N 12. The skeletal system. The Muscular System
Skeleton
A human skeleton - (endoskeleton)
In biology,
the skeleton (from Greek
σκελετός, "dried-up") or skeletal
system is the biological system providing physical support in living
organisms. (By extension, non-biological outline structures such as gantries or buildings
may also acquire skeletons.)
Types and classification
Skeletal systems are commonly divided
into three types - external (an exoskeleton), internal (an endoskeleton), and
fluid based (a hydrostatic skeleton), although hydrostatic skeletal systems may
be classified separately from the other two, because they lack hardened support
structures.
External skeletons
Large external systems support
proportionally less weight than endoskeletons of the same size, thus many
larger animals, such as the vertebrates, have internal skeletal systems. Examples of
exoskeletons are found in arthropods and shellfish, in which the skeleton forms a hard shell-like
covering protecting the internal organs.
The phyla Arthropoda and Mollusca
both have exoskeletons. Since exoskeletons necessarily limit growth, phyla with
exoskeletons have developed various solutions. Most mollusks have calcareous
shells and, as they grow, the diameter of the shell is enlarged without
altering its shape. On the other hand, arthropods shed their exoskeletons to
grow, a process known as ecdysis (or molting). During molting the arthropod
breaks down the old exoskeleton and then generates a new one, parts of which
then harden, through various processes (such as calcification or
sclerotization). An arthropod exoskeleton typically also has internal
extensions, commonly referred to as an endoskeleton, although it is not a true
endoskeleton.
Internal skeletons
An internal skeletal system
consists of rigid (or semi-rigid) structures, within the body, moved by the muscular
system. If the structures are mineralized or ossified,
as they are in humans and other mammals, they are referred to as bones. Cartilage
is another common component of skeletal systems, supporting and supplementing
the skeleton. The human ear
and nose
are shaped by cartilage. Some organisms have a skeleton consisting entirely of
cartilage and without any calcified bones at all, for example sharks. The bones or other
rigid structures are connected by ligaments
and connected to the muscular system via tendons.
Hydrostatic skeletons are similar to a
water-filled balloon. Located internally in cnidarians
(coral,
jellyfish
etc.) and annelids
(leeches,
earthworms etc.), among others, these animals can move by contracting the
muscles surrounding the fluid-filled pouch, creating pressure within the pouch
that causes movement. Animals such as earthworms use their hydrostatic
skeletons to change their body shape, as they move forward, from long and thin
to shorter and wider.
Skull classification
Amniotes,
a group of animals that have an endoskeleton can also be further classed by
their skeletons, specifically their skulls. The
number of holes (temporal fenestra) in the top of their crania
decide what class they fall into.
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Human Skull Anatomy Pictures |
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Function
The skeleton has six main
functions:
Support
The skeleton provides the
framework which supports the body, allowing large animals to maintain their
shape. And helps large animals to decrease its chance to have too much injury.
Attachment
The bones of the skeleton provide
an attachment surface for muscles, tendons
and ligaments.
Movement
Movement in vertebrates
is dependent on the skeletal muscles, which are attached to the skeleton by tendons.
Without the skeleton to give leverage, movement would be greatly restricted.
Protection
The skeleton protects many vital organs:
The skull protects the brain, the vertebral column protects the spinal cord,
and the ribcage protects the lungs and the heart.
] Blood cell
production
The skeleton is the site of haematopoiesis
- the generation of blood cells, that takes place in red bone marrow
(which is why bone marrow cancer is very often a terminal
disease)
Storage
Bone also serves as a mineral
storage deposit in which nutrients can be stored and retrieved. Calcium,
especially, can be released by dissolution of bone tissue under the control of 1,25-dihydroxyvitamin
D3 during periods of low calcium intake.
Organization
The human skeleton can be divided
into the axial skeleton and the appendicular skeleton.
The axial skeleton has five areas
and consists of 80 bones in a typical adult:
·
Skull
(22)
·
Ossicles
(bones of the middle ear) (6)
·
Hyoid bone
(bone in the throat) (1)
·
Vertebral
column (26)
·
Chest (25)
The appendicular skeleton has six
areas and consists of 126 bones in a typical adult:
·
Shoulder
girdle (4)
·
Arms (6)
·
Hands (54)
·
Pelvic girdle
(2)
·
Legs
(8)
·
Feet (52)
Human
newborns have over 270 bones some of which fuse together into a longitudinal
axis, the axial skeleton, to which the appendicular skeleton is attached.
Axial
skeleton
Diagram
of the axial skeleton
The
axial skeleton consists of the 80 bones along the central axis of the human
body. It is composed of six parts; the human skull, the ossicles of the middle
ear, the hyoid bone of the throat, the rib cage, sternum and the vertebral column.
The axial skeleton and the appendicular skeleton together form the complete
skeleton.
Flat
bones house the brain, spinal cord, and other vital organs. This article mainly
deals with the axial skeletons of humans; however, it is important to understand
the evolutionary lineage of the axial skeleton. The human axial skeleton
consists of 80 different bones. It is the midial core of the body and connects
the pelvis to the body, where the appendix skeleton attaches. As the skeleton
grows older the bones get weaker with the exception of the skull. The skull
remains strong to protect the brain from injury.
Etymology
The
word "Axial" is taken from the word "axis" and refers to
the fact that the bones are located close to or along the central axis of the
body.
Skull.
The human skull is a bony structure, part of the skeleton, that is in the human
head and which supports the structures of the face and forms a cavity for the
brain.
The
adult human skull is said to consist of two categorical parts of different embryological
origins: The neurocranium and the viscerocranium. The neurocranium (or
braincase) is a protective vault surrounding the brain and brain stem. The
viscerocranium (also splanchnocranium or facial skeleton) is formed by the
bones supporting the face.
Except
for the mandible, all of the bones of the skull are joined together by sutures,
synarthrodial (immovable) joints formed by bony ossification, with Sharpey's
fibres permitting some flexibility.
Human
skull side bones
Components
Skull
(22)
The
lower inner surface of the neurocranium
·
Cranial Bones (8)
·
Parietal (2)
·
Temporal (2)
·
Frontal (1)
·
Occipital (1)
·
Ethmoid (1)
·
sphenoid (1)
Various
sources provide different numbers for the count of constituent bones of the
human neuro- and viscerocranium. The reasons for such counting discrepancies
are numerous. Different textbooks classify the bones of the human skull
differently, e.g. they may (also) include (parts of) bones that are ordinarily
considered neurocranial bones in their list of facial bones. Some textbooks
count paired bones (where there is one bone on each side) only once instead of
twice. Some sources describe the maxilla's left and right parts as two bones.
Likewise, the palatine bone is also sometimes described as two bones. The hyoid
bone is usually not considered part of the skull, as it does not articulate
with any other bones, but some sources include it. Some sources include the
ossicles, three of which on each side are encased within the temporal bones,
though these are also usually not considered part of the skull. Extra sutural
bones may also variably be present, but they are not counted. For all of these
reasons, it may not be easy[2] to reach agreement on an authoritative bone
count for the neuro- and viscerocranium and the human skull. However, such
discrepancies between various sources are only differences in how to classify
and/or describe the anatomy of the human skull, and regardless of what
classification/description is used, the basic anatomy remains the same. With
that in mind, as one possible classification, the human skull could for example
be said to consist of twenty two bones: Eight bones of the neurocranium
(occipital bone, 2 temporal bones, 2 parietal bones, sphenoid bone, ethmoid
bone, frontal bone), and fourteen bones of the viscerocranium (vomer, 2
conchae, 2 nasal bones, 2 maxilla, mandible, 2 palatine bone, 2 zygomatic
bones, 2 lacrimal bones).
The
skull also contains the sinus cavities, which are air-filled cavities lined
with respiratory epithelium, which also lines the large airways. The exact
functions of the sinuses are debatable; they contribute to lessening the weight
of the skull with a minimal reduction in strength, they contribute to resonance
of the voice, and assist in the warming and moistening of air drawn in through
the nasal cavity.
Development
of the skull
The
lower inner surface of the neurocranium- 11 weeks' fertilization age
The
skull is a complex structure; its bones are formed both by intramembranous and
endochondral ossification. The skull roof, comprising the bones of the
splanchnocranium (face) and the sides and roof of the neurocranium, is formed
by intramembranous (or dermal) ossification, though the temporal bones are
formed by endochondral ossification. The endocranium, the bones supporting the
brain (the occipital, sphenoid, and ethmoid) are largely formed by endochondral
ossification. Thus frontal and parietal bones are purely membranous.[3] The
geometry of the cranial base and its fossas: anterior, middle and posterior
changes rapidly, especially during the first trimester of pregnancy. The first
trimester is crucial for development of skull defects.[4]
At
birth, the human skull is made up of 44 separate bony elements. As growth
occurs, many of these bony elements gradually fuse together into solid bone
(for example, the frontal bone). The bones of the roof of the skull are
initially separated by regions of dense connective tissue called
"fontanels". There are six fontanels: one anterior (or frontal), one
posterior (or occipital), two sphenoid (or anterolateral), and two mastoid (or
posterolateral). At birth these regions are fibrous and moveable, necessary for
birth and later growth. This growth can put a large amount of tension on the
"obstetrical hinge", which is where the squamous and lateral parts of
the occipital bone meet. A possible complication of this tension is rupture of
the great cerebral vein of Galen. As growth and ossification progress, the
connective tissue of the fontanelles is invaded and replaced by bone creating sutures.
The five sutures are the two squamous, one coronal, one lambdoid, and one
sagittal sutures. The posterior fontanel usually closes by eight weeks, but the
anterior fontanel can remain open up to eighteen months. The anterior fontanel
is located at the junction of the frontal and parietal bones; it is a
"soft spot" on a baby's forehead. Careful observation will show that
you can count a baby's heart rate by observing his or her pulse pulsing softly
through the anterior fontanel.
[edit]
Pathology
If
the brain is bruised or injured it can be life-threatening. Normally the skull
protects the brain from damage through its hard unyieldingness; the skull is
one of the least deformable structures found in nature with it needing the
force of about 1 ton to reduce the diameter of the skull by
Dating
back to Neolithic times, a skull operation called trepanation was sometimes
performed. This involved drilling holes in the cranium. Examination of skulls
from this period reveals that the "patients" sometimes survived for
many years afterward. It seems likely that trepanation was performed for
ritualistic or religious reasons and not only as an attempted life-saving
technique.
[edit]
Craniometry
and morphology of human skulls
Like
the face of a living individual, a human skull and teeth can also tell, to a
certain degree, the life history and origin of its owner. Forensic scientists
and archaeologists use metric and nonmetric traits to estimate what the bearer
of the skull looked like. When a significant amount of bones are found, such as
at Spitalfields in the UK and Jōmon shell mounds in Japan, osteologists
can use traits, such as the proportions of length, height and width, to know
the relationships of the population of the study with other living or extinct
populations.
The
German physician Franz Joseph Gall in around 1800 formulated the theory of
phrenology, which attempted to show that specific features of the skull are
associated with certain personality traits or intellectual capabilities of its
owner. This theory is now considered to be obsolete.
[edit]
Sexual
dimorphism
In
the past, specifically in the mid-nineteenth century, anthropologists found it
crucial to distinguish between male and female skulls. An anthropolgist of the
time, McGrigor Allan, argued that the female brain was similar to that of an
animal[6] . This allowed anthropologists to declare that women were in fact
more emotional and less like their rational male counterparts. McGrigor then
concluded that women’s brains were more analogous to infants, thus deeming them
inferior at the time[7] . To further these claims of female inferiority and
silence the feminists of the time, other anthropolgists joined in on the
studies of the female skull. These cranial measurements are the basis of what
is known as craniology. These cranial measurements were also used to draw a
connection between females and Negroes. French craniolgist, F. Pruner, went on
to describe this relationship as: “The Negro resemble[ing] the female in his
love for children, his family, and his cabin"[8] . Pruner also went on to
say that the negro is what the female is to the white man, “a loving being and
a being of pleasure”[9] . New forms of cranial measurement continued to
progress well into the early twentieth century in a effort to further implement
the sexual dimorphism between male and female skulls.
Research
today shows that while in early life there is little difference between male
and female skulls, in adulthood male skulls tend to be larger and more robust
than female skulls, which are lighter and smaller, with a cranial capacity
about 10 percent less than that of the male.[10] However, new studies show that
women's skulls are thicker and thus men may be more susceptible to head injury
than women.[11][12] The male body is larger than the female body, which
accounts for the larger size of the male skull; proportionally, the male skull
is about the same size as the female skull. Male skulls typically have more
prominent supraorbital ridges, a more prominent glabella, and more prominent
temporal lines. Female skulls generally have rounder orbits, and narrower jaws.
Male skulls on average have larger, broader palates, squarer orbits, larger
mastoid processes, larger sinuses, and larger occipital condyles than those of
females. Male mandibles typically have squarer chins and thicker, rougher
muscle attachments than female mandibles.
A
cross-section of a skull
Male
human skull
Child
viscerocranium
Anterior,
middle and posterior fossa
Bones
of human skull Endobasis-resistances
beams
Endobasis-resistances
beams
Endobasis-resistances
nodes
Auditory
Ossicles
Ossicles
(6 )
·
Malleus (2)
·
Incus (2)
·
Stapes (2)
Hyoid
bone
Hyoid
bone U-shape bone located in the neck. It
anchors the tongue and is associated with swallowing.
Vertebral
column
The
vertebral column, also known as backbone or spine, is a bony structure found in
Vertebrates. It is formed from the vertebrae. There are normally thirty-three (33)
vertebrae in humans, including the five that are fused to form the sacrum (the
others are separated by intervertebral discs) and the four coccygeal bones that
form the tailbone. The upper three regions comprise the remaining 24, and are
grouped under the names cervical (7 vertebrae), thoracic (12 vertebrae) and
lumbar (5 vertebrae), according to the regions they occupy. This number is
sometimes increased by an additional vertebra in one region, or it may be
diminished in one region, the deficiency often being supplied by an additional
vertebra in another. The number of cervical vertebrae is, however, very rarely
increased or diminished.[2]
Vertebral column
Divisions
of Spinal Segments
egmental
Spinal Cord Level and Function
|
Level |
Function |
|
C1-C6 |
Neck
flexors |
|
C1-T1 |
Neck
extensors |
|
C3,
C4, C5 |
Supply
diaphragm (mostly C4) |
|
C5,
C6 |
Shoulder
movement, raise arm (deltoid); flexion of elbow (biceps); C6 externally
rotates the arm (supinates) |
|
C6,
C7 |
Extends
elbow and wrist (triceps and wrist extensors); pronates wrist |
|
C7,
T1 |
Flexes
wrist |
|
C7,
T1 |
Supply
small muscles of the hand |
|
T1
-T6 |
Intercostals
and trunk above the waist |
|
T7-L1 |
Abdominal
muscles |
|
L1,
L2, L3, L4 |
Thigh
flexion |
|
L2,
L3, L4 |
Thigh
adduction |
|
L4,
L5, S1 |
Thigh
abduction |
|
L5,
S1, S2 |
Extension
of leg at the hip (gluteus maximus) |
|
L2,
L3, L4 |
Extension
of leg at the knee (quadriceps femoris) |
|
L4,
L5, S1, S2 |
Flexion
of leg at the knee (hamstrings) |
|
L4,
L5, S1 |
Dorsiflexion
of foot (tibialis anterior) |
|
L4,
L5, S1 |
Extension
of toes |
|
L5,
S1, S2 |
Plantar
flexion of foot |
|
L5,
S1, S2 |
Flexion
of toes |
With
the exception of the first and second cervical, the true or movable vertebrae
(the upper three regions) present certain common characteristics that are best
studied by examining one from the middle of the thoracic region.
Vertebral
Column (26)
·
Cervical vertebrae (7)
·
Thoracic vertebrae (12)
·
Lumbar vertebrae (5)
·
Sacrum (1) (5 at birth, later fused
in adult stage)
·
Coccyx (1) (4 at birth, later fused
to form one single bone, varies between 3-5)
Structure
of individual vertebrae
A
diagram of a human thoracic vertebra. Notice the articulations for the ribs
Oblique
view of cervical vertebrae.
A
typical vertebra consists of two essential parts: an anterior (front) segment,
which is the vertebral body; and a posterior part – the vertebral (neural) arch
– which encloses the vertebral foramen. The vertebral arch is formed by a pair
of pedicles and a pair of laminae, and supports seven processes, four
articular, two transverse, and one spinous, the latter also being known as the
neural spine.
When
the vertebrae are articulated with each other, the bodies form a strong pillar
for the support of the head and trunk, and the vertebral foramina constitute a
canal for the protection of the medulla spinalis (spinal cord). In between
every pair of vertebrae are two apertures, the intervertebral foramina, one on
either side, for the transmission of the spinal nerves and vessels.
Two
transverse processes and one spinous process are posterior to (behind) the
vertebral body. The spinous process comes out the back, one transverse process
comes out the left, and one on the right. The spinous processes of the cervical
and lumbar regions can be felt through the skin.
Superior
and inferior articular facets on each vertebra act to restrict the range of
movement possible. These facets are joined by a thin portion of the neural arch
called the pars interarticularis.
Curves
Viewed
laterally the vertebral column presents several curves, which correspond to the
different regions of the column, and are called cervical, thoracic, lumbar, and
pelvic.
The
cervical curve, convex forward, begins at the apex of the odontoid (tooth-like)
process, and ends at the middle of the second thoracic vertebra; it is the
least marked of all the curves.
The
thoracic curve, concave forward, begins at the middle of the second and ends at
the middle of the twelfth thoracic vertebra. Its most prominent point behind
corresponds to the spinous process of the seventh thoracic vertebra. This curve
is known as a tt curve.
The
lumbar curve is more marked in the female than in the male; it begins at the
middle of the last thoracic vertebra, and ends at the sacrovertebral angle. It
is convex anteriorly, the convexity of the lower three vertebrae being much
greater than that of the upper two. This curve is described as a lordotic
curve.
The
pelvic curve begins at the sacrovertebral articulation, and ends at the point
of the coccyx; its concavity is directed downward and forward.
The
thoracic and pelvic curves are termed primary curves, because they alone are
present during fetal life. The cervical and lumbar curves are compensatory or
secondary, and are developed after birth, the former when the child is able to
hold up its head (at three or four months) and to sit upright (at nine months),
the latter at twelve or eighteen months, when the child begins to walk.
Regions
Orientation
of vertebral column on surface. T3 is at level of medial part of spine of
scapula. T7 is at inferior angle of the scapula. L4 is at highest point of
iliac crest. S2 is at the level of posterior superior iliac spine. Furthermore,
C7 is easily localized as a prominence at the lower part of the neck.[3]
There
are a total of 33 vertebrae in the vertebral column, if assuming 4 coccygeal
vertebrae.
The
individual vertebrae, named according to region and position, from superior to
inferior, are:
·
Cervical: 7 vertebrae (C1–C7)
·
Thoracic: 12 vertebrae (T1–T12)
·
Lumbar: 5 vertebrae (L1–L5)
·
Sacral: 5 (fused) vertebrae (S1–S5)
·
Coccygeal: 4 (3–5) (fused) vertebrae
(Tailbone)
Cervical
There
are seven (7) cervical bones (but 8 cervical spinal nerves) and these bones
are, in general, small and delicate. Their spinous processes are short (with
the exception of C2 and C7, which have palpable spinous processes). Numbered
top-to-bottom from C1-C7, atlas (C1) and axis (C2), are the vertebrae that
allow the neck and head so much movement. For the most part, the
atlanto-occipital joint allows the skull to move up and down, while the
atlanto-axial joint allows the upper neck to twist left and right. The axis
also sits upon the first intervertebral disk of the spinal column. All mammals
except manatees and sloths have seven cervical vertebrae, whatever the length
of the neck.
Cervical
vertebrae possess transverse foramina to allow for the vertebral arteries to
pass through on their way to the foramen magnum to end in the circle of Willis.
These are the smallest, lightest vertebrae and the vertebral foramina are
triangular in shape. The spinous processes are short and often bifurcated (the
spinous process of C7, however, is not bifurcated, and is substantially longer
than that of the other cervical spinous processes).
The
term cervicothoracic is often used to refer to the cervical and thoracic
vertebrae together, and sometimes also their surrounding areas.
Thoracic
The
twelve (12) thoracic bones and their transverse processes have surfaces that
articulate with the ribs. Some rotation can occur between the thoracic
vertebrae, but their connection with the rib cage prevents much flexion or
other excursion. They may also be known as 'dorsal vertebrae', in the human
context.
Bodies
are roughly heart-shaped and are about as wide anterio-posterioly as they are
in the transverse dimension. Vertebral foramina are roughly circular in shape.
The
term thoracolumbar is sometimes used to refer to the thoracic and lumbar
vertebrae together, and sometimes also their surrounding areas.
Lumbar
These
five (5) vertebrae are very robust in construction, as they must support more
weight than other vertebrae. They allow significant flexion, extension and
moderate lateral flexion (sidebending). The discs between these vertebrae
create a lumbar lordosis (curvature that is concave posteriorly) in the human spine.
The
term lumbosacral is often used to refer to the lumbar and sacral vertebrae
together, and sometimes also their surrounding areas.
Sacral
There
are five (5) vertebrae (S1-S5) which are fused in maturity, with no
intervertebral discs. The 5 fused bones are collectively known as the sacrum.
Coccygeal
There
are usually four (4) and rarely 3 or 5 vertebrae (Co1-Co5), with no
intervertebral discs. Many animals have a greater number of "tail
vertebrae," and, in animals, they are more commonly known as "caudal
vertebrae." Pain at the coccyx (tailbone) is known as coccydynia.
Development
The
striking segmented pattern of the human spine is established during
embryogenesis when the precursor of the vertebrae, the somites, are rhythmically
added to the forming posterior part of the embryo. In humans, somite formation
begins around the third week post-fertilization and continues until a total of
around 52 somites are formed. The somites are epithelial spheres that contain
the precursors of the vertebrae, the ribs, the skeletal muscles of the body
wall and limbs, and the dermis of the back. The periodicity of somite
distribution and production is thought to be imposed by a molecular oscillator
or clock acting in cells of the presomitic mesoderm (PSM). Somites form soon
after the beginning of gastrulation, on both sides of the neural tube from a
tissue called the presomitic mesoderm (PSM). The PSM is part of the paraxial
mesoderm and is generated caudally by gastrulation when cells ingress through
the primitive streak, and later, through the tail bud. Soon after their
formation, somites become subdivided into the dermomyotome dorsally, which
gives rise to the muscles and dermis, and the sclerotome ventrally, which will
form the spine components. Sclerotomes become subvidided into an anterior and a
posterior compartment. This subdivision plays a key role in the definitive
patterning of vertebrae that form when the posterior part of one somite fuses
to the anterior part of the consecutive somite during a process termed
resegmentation. Disruption of the somitogenesis process in humans results in
diseases such as congenital scoliosis. So far, the human homologues of three
genes associated to the mouse segmentation clock (MESP2, DLL3 and LFNG) have
been shown to be mutated in human patients with human congenital scoliosis
suggesting that the mechanisms involved in vertebral segmentation are conserved
across vertebrates. In humans the first four somites are incorporated in the
basi-occipital bone of the skull and the next 33 somites will form the
vertebrae.[6] The remaining posterior somites degenerate. During the fourth
week of embryonic development, the sclerotomes shift their position to surround
the spinal cord and the notochord. The sclerotome is made of mesoderm and
originates from the ventromedial part of the somites. This column of tissue has
a segmented appearance, with alternating areas of dense and less dense
areas.[citation needed]
As
the sclerotome develops, it condenses further eventually developing into the
vertebral body. Development of the appropriate shapes of the vertebral bodies
is regulated by HOX genes.
The
less dense tissue that separates the sclerotome segments develop into the
intervertebral discs.
The
notochord disappears in the sclerotome (vertebral body) segments, but persists
in the region of the intervertebral discs as the nucleus pulposus. The nucleus
pulposus and the fibers of the annulus fibrosus make up the intervertebral
disc.
The
primary curves (thoracic and sacral curvatures) form during fetal development.
The secondary curves develop after birth. The cervical curvature forms as a
result of lifting the head and the lumbar curvature forms as a result of
walking.
Unfused
arch of C1 at CT.
There
are various defects associated with vertebral development. Scoliosis will
result in improper fusion of the vertebrae. In Klippel-Feil anomaly patients
have two or more cervical vertebrae that are fused together, along with other
associated birth defects. One of the most serious defects is failure of the
vertebral arches to fuse. This results in a condition called spina bifida.
There are several variations of spina bifida that reflect the severity of the
defect.
Surfaces
Anterior
surface
The
vertebrae may be used as vertical reference points to describe the locations of
the organs of the trunk, such as with the transpyloric line (seen at body of
L1). If not else specified, it is usually the middle of the vertebral body that
is used as reference, although the palpable spinous processes may be located
considerably lower.
When
viewed from in front, the width of the bodies of the vertebrae is seen to
increase from the second cervical to the first thoracic; there is then a slight
diminution in the next three vertebrae; below this there is again a gradual and
progressive increase in width as low as the sacrovertebral angle. From this
point there is a rapid diminution, to the apex of the coccyx.
Posterior
surface
Orientation
of the rib cage on the vertebral column
The
posterior surface of the vertebral column presents in the median line the
spinous processes. In the cervical region (with the exception of the second and
seventh vertebrae) these are short and horizontal, with bifid extremities. In
the upper part of the thoracic region they are directed obliquely downward; in
the middle they are almost vertical, and in the lower part they are nearly
horizontal. In the lumbar region they are nearly horizontal. The spinous
processes are separated by considerable intervals in the lumbar region, by
narrower intervals in the neck, and are closely approximated in the middle of
the thoracic region. Occasionally one of these processes deviates a little from
the median line — a fact to be remembered in practice, as irregularities of this
sort are attendant also on fractures or displacements of the vertebral column.
On either side of the spinous processes is the vertebral groove formed by the
laminae in the cervical and lumbar regions, where it is shallow, and by the
laminae and transverse processes in the thoracic region, where it is deep and
broad; these grooves lodge the deep muscles of the back. Lateral to the
vertebral grooves are the articular processes, and still more laterally the
transverse processes. In the thoracic region, the transverse processes stand
backward, on a plane considerably behind that of the same processes in the
cervical and lumbar regions. In the cervical region, the transverse processes
are placed in front of the articular processes, lateral to the pedicles and between
the intervertebral foramina. In the thoracic region they are posterior to the
pedicles, intervertebral foramina, and articular processes. In the lumbar
region they are in front of the articular processes, but behind the
intervertebral foramina.
Lateral
surfaces
The
lateral surfaces are separated from the posterior surface by the articular
processes in the cervical and lumbar regions, and by the transverse processes
in the thoracic region. They present, in back, the sides of the bodies of the
vertebrae, marked in the thoracic region by the facets for articulation with
the heads of the ribs. More posteriorly are the intervertebral foramina, formed
by the juxtaposition of the vertebral notches, oval in shape, smallest in the
cervical and upper part of the thoracic regions, and gradually increasing in
size to the last lumbar. They transmit the special spinal nerves and are
situated between the transverse processes in the cervical region, and in front
of them in the thoracic and lumbar regions.
Vertebral
canal
The
vertebral canal follows the different curves of the column; it is large and
triangular in those parts of the column which enjoy the greatest freedom of
movement, such as the cervical and lumbar regions; and is small and rounded in
the thoracic region, where motion is more limited.
Abnormalities
Occasionally
the coalescence of the laminae is not completed, and consequently a cleft is
left in the arches of the vertebrae, through which a protrusion of the spinal
membranes (dura mater and arachnoid), and generally of the spinal cord (medulla
spinalis) itself, takes place, constituting the malformation known as spina
bifida. This condition is most common in the lumbosacral region, but it may
occur in the thoracic or cervical region, or the arches throughout the whole
length of the canal may remain incomplete.
The
following abnormal curvatures may occur in some people:
Kyphosis
is an exaggerated kyphotic (posterior) curvature in the thoracic region. This
produces the so-called "humpback" or "dowager's hump", a
condition commonly observed in osteoporosis.
Lordosis
is an exaggerated lordotic (anterior) curvature of the lumbar region,
"swayback". Temporary lordosis is common among pregnant women.
Retrolisthesis
is a posterior displacement of one vertebral body with respect to the adjacent
vertebral segment to a degree less than a luxation (dislocation).
Scoliosis, lateral curvature,
is the most common abnormal curvature, occurring in 0.5% of the population. It
is more common among females and may result from unequal growth of the two
sides of one or more vertebrae. It can also be caused by pulmonary atelectasis
(partial or complete deflation of one or more lobes of the lungs) as observed
in asthma or pneumothorax.
The
spinal cord nested in the vertebral column.
Relation
of the vertebral column to the surrounding muscles.
Chest
Thoracic
cage (27)
·
Sternum (3) - Manubrium (1) Body of
sternum (1) Xiphoid process (1)
·
Ribs (24)
The
appendicular skeleton is composed of 126 bones in the human body. The word
appendicular is the adjective of the noun appendage, which itself means a part
that is joined to something larger. Functionally it is involved in locomotion
(Lower limbs) of the axial skeleton and manipulation of objects in the
environment (Upper limbs).
The
appendicular skeleton forms during development from cartlilage, by the process
of endochondral ossification.
The
appendicular skeleton is divided into six major regions:
1) Pectoral Girdles (4 bones) - Left and right
Clavicle (2) and Scapula (2).
Left and right clavicle: in human anatomy, the clavicle or
collarbone is a long bone of short length that serves as a strut between the
scapula and the sternum. It is the only long bone in the body that lies
horizontally. It makes up part of the shoulder and the pectoral girdle and is
palpable in all people, and, in people who have less fat in this region, the
location of the bone is clearly visible as it creates a bulge in the skin. It
receives its name from the Latin: clavicula ("little key") because
the bone rotates along its axis like a key when the shoulder is abducted.
Bone:
Clavicle
Human
anatomy
Right
clavicle — from below, and from above.
Left
clavicle — from above, and from below.
The
clavicle is a doubly curved short bone that connects the arm (upper limb) to
the body (trunk), located directly above the first rib. It acts as a strut to
keep the scapula in place so the arm can hang freely. Medially, it articulates
with the manubrium of the sternum (breast-bone) at the sternoclavicular joint.
At its lateral end it articulates with the acromion of the scapula (shoulder
blade) at the acromioclavicular joint. It has a rounded medial end and a
flattened lateral end.
From
the roughly pyramidal sternal end, each clavicle curves laterally and
anteriorly for roughly half its length. It then forms a smooth posterior curve
to articulate with a process of the scapula (acromion). The flat acromial end
of the clavicle is broader than the sternal end. The acromial end has a rough
inferior surface that bears prominent line, Trapezoid line and a small rounded
projection, Conoid tubercle. These surface features are attachment sites for
muscles and ligaments of the shoulder.
It
can be divided into three parts: medial end, lateral end and shaft.
Medial
end
The
medial end is the quadrangular and articulates with the clavicular notch of the
menubrium sterni to form the sternoclavicular joint. The articular surface
extends to the inferior aspect for attachment with the first costal cartilage.
It
gives attachments to:
fibrous
capsule joint all around
articular
disc superoposteriorly
interclavicular
ligament superiorly
Lateral
end
The
lateral end is flat from above downward. It bears a facet for attachment to the
acromion process of the scapula, forming the acromioclavicular joint. The area
surrounding the joint gives an attachment to the joint capsule.
Shaft
The
shaft is divided into medial 2/3 and lateral 1/3. The medial 2/3 is thicker
than the lateral 1/3.
Medial
2/3 of the shaft
The
medial 2/3 of the shaft has four surfaces and no borders.
The
anterior surface is convex forward and gives origin to pectoralis major.
Posterior surface is smooth and gives origin to sternohyoid muscle at its
medial end. Superior surface is rough at its medial part and gives origin to
sternocleidomastoid muscle . Inferior surface has an oval impression at its
medial end for costoclavicular ligament. At the lateral side of inferior
surface, there is a subclavian groove for insertion of subclavius muscle. At
the lateral side of subclavian groove, nutrient foramen lies. The medial part
is quadangular in shape where it makes a joint with the manubrium of the
sternum at sternoclavicular joint. The margins of subclavian groove gives
attachment to the clavipectoral fascia.
Lateral
1/3 of the shaft
The
lateral 1/3 of the shaft has two borders and two surfaces.
The
Anterior border is concave forward and gives origin to the deltoid muscle. The
Posterior border is convex backward and gives attachment to the trapezius
muscle . The
Attachments
Muscles
and ligaments that attach to the clavicle include:
|
Attachment
on clavicle |
Muscle/Ligament |
Other
attachment |
|
Superior
surface and anterior border |
Deltoid
muscle |
deltoid
tubercle, anteriorly on the lateral third |
|
Superior
surface |
Trapezius
muscle |
posteriorly
on the lateral third |
|
Inferior
surface |
Subclavius
muscle |
subclavian
groove |
|
Inferior
surface |
Conoid
ligament (the medial part of the coracoclavicular ligament) |
conoid
tubercle |
|
Inferior
surface |
Trapezoid
ligament (the lateral part of the coracoclavicular ligament) |
trapezoid
line |
|
Anterior
border |
Pectoralis
major muscle |
medial
third (rounded border) |
|
Posterior
border |
Sternocleidomastoid
muscle (clavicular head) |
superiorly,
on the medial third |
|
Posterior
border |
Sternohyoid
muscle |
inferiorly,
on the medial third |
|
Posterior
border |
Trapezius
muscle |
lateral
third |
The
levator claviculae muscle, present in 2–3% of people, originates on the
transverse processes of the upper cervical vertebrae and is inserted in the
lateral half of the clavicle.
Functions
The
clavicle serves several functions:
It
serves as a rigid support from which the scapula and free limb (arm) are
suspended; an arrangement that keeps the upper limb away from the thorax so
that the arm has maximum range of movement. Acting as flexible, crane-like
strut, it allows the scapula to move freely on the thoracic wall.
Covering
the cervicoaxillary canal, it protects the neurovascular bundle that supplies
the upper limb.
Transmits
physical impacts from the upper limb to the axial skeleton.
Development
The
clavicle is the first bone to begin the process of ossification (laying down of
minerals onto a preformed matrix) during development of the embryo, during the
5th and 6th weeks of gestation. However, it is one of the last bones to finish
ossification at about 21–25 years of age, and a study measuring 748 males and
252 females saw a difference in clavicle length between age groups 18-20 and
21-25 of about 6 and
Even
though it is classified as a long bone, the clavicle has no medullary (bone
marrow) cavity like other long bones, though this is not always true.[citation
needed] It is made up of spongy (trabecular) bone with a shell of compact bone.
It is a dermal bone derived from elements originally attached to the skull.
Variations
The
shape of the clavicle varies more than most other long bones. It is
occasionally pierced by a branch of the supraclavicular nerve. In males it is
thicker and more curved and the sites of muscular attachments are more
pronounced. The right clavicle is usually stronger and shorter than the left
clavicle. In females the clavicle is thinner, smoother and lighter than that of
males. Clavicle form is a reliable criterion for sex determination.
The
collarbones are sometimes partly or completely absent in cleidocranial
dysostosis.
Common
clavicle injuries
Acromioclavicular
dislocation ("AC Separation")
Clavicle
fractures
Degeneration
of the clavicle
Osteolysis
Sternoclavicular
dislocations
Evolutionary
variation
The
clavicle first appears as part of the skeleton in primitive bony fish, where it
is associated with the pectoral fin; they also have a bone called the
cleithrum. In such fish, the paired clavicles run behind and below the gills on
each side, and are joined by a solid symphysis on the fish's underside. They
are, however, absent in cartilagenous fish and in the vast majority of living
bony fish, including all of the teleosts.
The
earliest tetrapods retained this arrangement, with the addition of a
diamond-shaped interclavicle between the base of the clavicles, although this
is not found in living amphibians. The cleithrum disappeared early in the
evolution of reptiles, and is not found in any living amniotes, but the
interclavicle is present in most modern reptiles, and also in monotremes. In
modern forms, however, there are a number of variations from the primitive
pattern. For example, crocodilians and salamanders lack clavicles altogether
(although crocodilians do retain the interclavicle), while in turtles, they
form part of the armoured plastron.
In
birds, the clavicles and interclavicle have fused to form a single Y-shaped
bone, the furcula or "wishbone".
The
interclavicle is absent in marsupials and placental mammals. In many mammals,
the clavicles are also reduced, or even absent, to allow the scapula greater
freedom of motion, which may be useful in fast-running animals.
Though
a number of fossil hominin (humans and chimpanzees) clavicles have been found,
most of these are mere segments offering limited information on the form and
function of the pectoral girdle. One exception is the clavice of AL 333x6/9
attributed to Australopithecus afarensis which has a well-preserved sternal
end. One interpretation of this specimen, based on the orientation of its
lateral end and the position of the deltoid attachment area, suggests that this
clavicle is distinct from those found in extant apes (including humans), and
thus that the shape of the human shoulder dates back to less than 3 to 4
million years ago. However, analyses of the clavicle in extant primates suggest
that the low position of the scapula in humans is reflected mostly in the
curvature of the medial portion of the clavicle rather than the lateral
portion. This part of the bone is similar in A. afarensis and it is thus
possible that this species had a high shoulder position similar to that in
modern humans.
Human
arm bones diagram
Diagram
of the human shoulder joint
Sternoclavicular
articulation. Anterior view.
The
left shoulder and acromioclavicular joints, and the proper ligaments of the
scapula.
Muscles
of the neck. Lateral view.
Muscles
of the neck. Anterior view.
Anterolateral
view of head and neck.
Front
view of neck.
Clavicle
Clavicle
Scapula: In anatomy, the scapula (Medical Latin), or
shoulder blade, is the bone that connects the humerus (upper arm bone) with the
clavicle (collar bone).
The
scapula forms the posterior (back) located part of the shoulder girdle. In
humans, it is a flat bone, roughly triangular in shape, placed on a
posterolateral aspect of the thoracic cage.
A
posterior view of the thorax (scapula shown in red.)
Surfaces
Costal
(Front, Ventral, Anterior)
The
costal or ventral surface [Fig. 1] presents a broad concavity, the subscapular
fossa.
1.
Subscapular fossa
2. Glenoid cavity
3. Coracoid process
4. Acromion
5. Superior border
6. Scapular notch
7. Superior angle
8. Medial border
9. Inferior angle
10. Lateral border
11. Infraglenoid tubercle
Dorsal
(Back, Posterior)
The
dorsal surface [Fig. 2] is arched from above downward, and is subdivided into
two unequal parts by the spine; the portion above the spine is called the
supraspinous fossa, and that below it the infraspinous fossa.
The
supraspinous fossa, the smaller of the two, is concave, smooth, and broader at
its vertebral than at its humeral end; its medial two-thirds give origin to the
Supraspinatus.
The
infraspinous fossa is much larger than the preceding; toward its vertebral
margin a shallow concavity is seen at its upper part; its center presents a
prominent convexity, while near the axillary border is a deep groove which runs
from the upper toward the lower part. The medial two-thirds of the fossa give
origin to the Infraspinatus; the lateral third is covered by this muscle.
The
dorsal surface is marked near the axillary border by an elevated ridge, which
runs from the lower part of the glenoid cavity, downward and backward to the vertebral
border, about
The
ridge serves for the attachment of a fibrous septum, which separates the
Infraspinatus from the Teres major and Teres minor.
The
surface between the ridge and the axillary border is narrow in the upper
two-thirds of its extent, and is crossed near its center by a groove for the
passage of the scapular circumflex vessels; it affords attachment to the Teres
minor.
The
costal surface superior of the scapula is the origin of 1st digitation for the
serratus anterior origin. The broad and narrow portions above alluded to are
separated by an oblique line, which runs from the axillary border, downward and
backward, to meet the elevated ridge: to it is attached a fibrous septum which
separates the Teres muscles from each other.
Its
lower third presents a broader, somewhat triangular surface, which gives origin
to the Teres major, and over which the Latissimus dorsi glides; frequently the
latter muscle takes origin by a few fibers from this part.
Figure
1 : Left scapula. Costal surface.
The
medial two-thirds of this fossa are marked by several oblique ridges, which run
lateralward and upward. The ridges give attachment to the tendinous insertions,
and the surfaces between them to the fleshy fibers, of the Subscapularis. The
lateral third of the fossa is smooth and covered by the fibers of this muscle.
At
the upper part of the fossa is a transverse depression, where the bone appears
to be bent on itself along a line at right angles to and passing through the
center of the glenoid cavity, forming a considerable angle, called the
subscapular angle; this gives greater strength to the body of the bone by its
arched form, while the summit of the arch serves to support the spine and
acromion.
1.
Supraspinatous fossa
2. Spine
3. Infraspinatous fossa
4. Superior border
5. Superior angle
6. Medial border
7. Inferior angle
8. Lateral border
9. Lateral angle
10. Acromion
11. Coracoid process
12. Orgin of teres major muscle
13. Orgin of teres minor muscle
Figure
2 : Left scapula. Dorsal surface.
Borders
There
are three borders of the scapula:
The
superior border is the shortest and thinnest; it is concave, and extends from
the medial angle to the base of the coracoid process. It is referred to as the
cranial border in animals.
The
axillary border (or "lateral border") is the thickest of the three.
It begins above at the lower margin of the glenoid cavity, and inclines
obliquely downward and backward to the inferior angle. It is referred to as the
caudal border in animals.
The
vertebral border (or "medial border") is the longest of the three,
and extends from the medial to the inferior angle. It is referred to as the
dorsal border in animals.
Angles
There
are 3 angles
·
The superior angle is covered by
trapezius.
·
The inferior angle is covered by
latissimus dorsi. It moves forwards round the chest when the arm is abducted.
·
The lateral or glenoid angle is broad
and bears the glenoid cavity or fossa, which is directed forward, laterally and
slightly upwards.
The
acromion
The
acromion forms the summit of the shoulder, and is a large, somewhat triangular
or oblong process, flattened from behind forward, projecting at first
laterally, and then curving forward and upward, so as to overhang the glenoid
cavity.
Figure
3 : Left scapula. Lateral surface.
1.
Coracoid process
2. Glenoid cavity
3. Supraspinatous fossa
4. Acromion
5. Infraspinatous fossa
6. Inferior angle
7. Lateral border
Development
Main
article: ossification of scapula
The
larger part of the scapula undergoes membranous ossification.. Some of the
outer parts of the scapula are cartilaginous at birth, and would therefore
undergo endochondral ossification .
The
head, processes, and the thickened parts of the bone, contain cancellous
tissue; the rest consists of a thin layer of compact tissue.
The
central part of the supraspinatus fossa and the upper part of the
infraspinatous fossa, but especially the former, are usually so thin in humans
as to be semitransparent; occasionally the bone is found wanting in this
situation, and the adjacent muscles are separated only by fibrous tissue.
Muscular
attachments
The
following muscles attach to the scapula:
|
Muscle |
Direction |
Region |
|
Pectoralis
Minor |
insertion |
coracoid
process |
|
Coracobrachialis |
origin |
coracoid
process |
|
Serratus
Anterior |
insertion |
medial
border |
|
Triceps
Brachii (long head) |
origin |
infraglenoid
tubercle |
|
Biceps
Brachii (short head) |
origin |
coracoid
process |
|
Biceps
Brachii (long head) |
origin |
supraglenoid
tubercle |
|
Subscapularis |
origin |
subscapular
fossa |
|
Rhomboid
Major |
insertion |
medial
border |
|
Rhomboid
Minor |
insertion |
medial
border |
|
Levator
Scapulae |
insertion |
medial
border |
|
Trapezius |
insertion |
spine
of scapula |
|
Deltoid |
origin |
spine
of scapula |
|
Supraspinatus |
origin |
supraspinous
fossa |
|
nfraspinatus |
origin |
infraspinous
fossa |
|
Teres
Minor |
origin |
lateral
border |
|
Teres
Major |
origin |
lateral
border |
|
Latissimus
Dorsi (a few fibers) |
origin |
inferior
angle |
|
Omohyoid |
origin |
superior border |
Movements
Movements
of the scapula are brought about by scapular muscles:
Elevation,
Depression, Protraction (abduction) Retraction (adduction) Upward (lateral)
rotation, Downward (medial) rotation, Anterior Tipping, and Posterior Tipping
Injury
Main
article: Scapular fracture
Because
of its sturdy structure and protected location, scapular fractures are
uncommon; when they do occur, they are an indication that severe chest trauma
has occurred.
A
winged scapula is a condition in which the medial border (the side nearest the
spine) of a person's scapula is abnormally positioned outward and backward. The
resulting appearance of the upper back is said to be wing-like because the
inferior angle of the shoulder blade protrudes backward rather than lying mostly
flat. In addition, any condition causing weakness of the serratus anterior
muscle may cause scapular "winging".
Shoulder
Impingement Syndrome and the Scapula
The
scapula has been found to play an important role in shoulder impingement
syndrome. It is a wide, flat bone lying
on the thoracic wall that provides an attachment for three different groups of
muscles. The intrinsic muscles of the scapula include the muscles of the
rotator cuff- the subscapularis, teres minor, supraspinatus, and infraspinatus.
These muscles attach to the surface of the scapula and are responsible for the
internal and external rotation of the glenohumeral joint, along with humeral
abduction. The extrinsic muscles include the biceps, triceps, and deltoid
muscles and attach to the coracoid process and supraglenoid tubercle of the
scapula, infraglenoid tubercle of the scapula, and spine of the scapula. These
muscles are responsible for several actions of the glenohumeral joint. The
third group, which is mainly responsible for stabilization and rotation of the
scapula, consists of the trapezius, serratus anterior, levator scapulae, and
rhomboid muscles and attach to the medial, superior, and inferior borders of
the scapula. Each of these muscles has their own role in proper shoulder
function and must be in balance with each other in order to avoid shoulder
pathology. Abnormal scapular function is called scapular dyskinesis. One action
the scapula performs during a throwing or serving motion is elevation of the
acromion process in order to avoid impingement of the rotator cuff tendons. If
the scapula fails to properly elevate the acromion, impingement may occur
during the cocking and acceleration phase of an overhead activity. The two
muscles most commonly inhibited during this first part of an overhead motion
are the serratus anterior and the lower trapezius. These two muscles act as a
force couple within the glenohumeral joint to properly elevate the acromion
process, and if a muscle imbalance exists, shoulder impingement may develop.
In
other animals
Scapulae,
spine and ribs of Myotis lucifugus (Little Brown Bat).
In
fish, the scapular blade is a structure attached to the upper surface of the
articulation of the pectoral fin, and is accompanied by a similar coracoid
plate on the lower surface. Although sturdy in cartilagenous fish, both plates
are generally small in most other fish, and may be partially cartilagenous, or
consist of multiple bony elements.
In
the early tetrapods, these two structures respectively became the scapula and a
bone referred to as the procoracoid (commonly called simply the
"coracoid", but not homologous with the mammalian structure of that
name). In amphibians and reptiles (birds included), these two bones are
distinct, but together form a single structure bearing many of the muscle
attachments for the forelimb. In such animals, the scapula is usually a
relatively simple plate, lacking the projections and spine that it possesses in
mammals. However, the detailed structure of these bones varies considerably in
living groups. For example, in frogs, the procoracoid bones may be braced
together at the animal's underside to absorb the shock of landing, while in
turtles, the combined structure forms a Y-shape in order to allow the scapula
to retain a connection to the clavicle (which is part of the shell). In birds,
the procoracoids help to brace the wing against the top of the sternum.
In
the fossil therapsids, a third bone, the true coracoid, formed just behind the
procoracoid. The resulting three-boned structure is still seen in modern
monotremes, but in all other living mammals, the procoracoid has disappeared,
and the coracoid bone has fused with the scapula, to become the coracoid
process. These changes are associated with the upright gait of mammals, compared
with the more sprawling limb arrangement of reptiles and amphibians; the
muscles formerly attached to the procoracoid are no longer required. The
altered musculature is also responsible for the alteration in the shape of the
rest of the scapula; the forward margin of the original bone became the spine
and acromion, from which the main shelf of the shoulder blade arises as a new
structure.
2)
Arm and Forearm (6 bones) - Left and right Humerus (2) (Arm), Ulna (2) and
Radius (2) (Fore Arm).
Arm and Forearm (6 bones) - Left and right Humerus (2) (Arm),
Ulna (2) and Radius (2) (Fore Arm).
The humerus (pron.:
/ˈhjuːmərəs/; ME from Latin humerus, umerus upper arm,
shoulder; cf. Gothic ams shoulder, Greek ōmos. Plural: humeri) is a long bone
in the arm or forelimb that runs from the shoulder to the elbow.
Anatomically,
it connects the scapula and the lower arm (consisting of the radius and ulna),
and consists of three sections. The upper extremity consists of a rounded head,
a narrow neck, and two short processes (tubercles, sometimes called
tuberosities.) Its body is cylindrical in its upper portion, and more prismatic
below. The lower extremity consists of 2 epicondyles, 2 processes (trochlea
& capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon
fossa). As well as its true anatomical neck, the constriction below the greater
and lesser tubercles of the humerus is referred to as its surgical neck due to
its tendency to commonly get fractured, thus often becoming the focus of
surgeons.
Position
of humerus (shown in red). Anterior view.
Muscles
attached to the humerus
The
deltoid originates on the lateral third of the clavicle, acromion and the crest
of the spine of the scapula. It is inserted on the deltoid tuberosity of the
humerus and has several actions including abduction, extension, and
circumduction of the shoulder. The supraspinatus also originates on the spine
of the scapula. It inserts on the greater tubercle of the humerus, and assists
in abduction of the shoulder.
The
pectoralis major, teres major, and latissimus dorsi insert at the
intertubercular groove of the humerus. They work to adduct and medially, or
internally, rotate the humerus.
The
infraspinatus and teres minor insert on the greater tubercle, and work to
laterally, or externally, rotate the humerus. In contrast, the subscapularis
muscle inserts onto the lesser tubercle and works to medially, or internally,
rotate the humerus.
The
biceps brachii, brachialis, and brachioradialis (which attaches distally) act
to flex the elbow. (The biceps, however, does not attach to the humerus.) The
triceps brachii and anconeus extend the elbow, and attach to the posterior side
of the humerus.
The
four muscles of supraspinatus, infraspinatus, teres minor and subscapularis
form a musculo-ligamentous girdle called the rotator cuff. This cuff stabilizes
the very mobile but inherently unstable glenohumeral joint. The other muscles
are used as counterbalances for the actions of lifting/pulling and
pressing/pushing.
Left
humerus. Anterior view
A.
Supraspinatus muscle
B. Latissimus dorsi muscle
C. Pectoralis major muscle
D. Deltoid muscle
E. Brachioradialis
F. Extensor carpi radialis longus muscle
G.
H. Subscapularis muscle
I. Teres major muscle
J. Coracobrachialis muscle
K. Brachialis muscle
L. Pronator teres muscle
Left humerus. Posterior view
Articulations
At
the shoulder, the head of the humerus articulates with the glenoid fossa of the
scapula. More distally, at the elbow, the capitulum of the humerus articulates
with the head of the radius, and the trochlea of the humerus articulates with
the trochlear notch of the ulna.
The
left shoulder and acromioclavicular joints, and the proper ligaments of the
scapula.
Head
of humerus
The
Supinator
Nerves
The
axillary nerve is located at the proximal end, against the shoulder girdle.
Dislocation of the humerus's glenohumeral joint, has the potential to injure
the axillary nerve or the axillary artery. Signs and symptoms of this
dislocation include a loss of the normal shoulder contour and a palpable
depression under the acromion.
The
radial nerve follows the humerus closely. At the midshaft of the humerus, the
radial nerve travels from the posterior to the anterior aspect of the bone in
the spiral groove. A fracture of the humerus in this region can result in
radial nerve injury.
The
ulnar nerve at the distal end of the humerus near the elbow is sometimes
referred to in popular culture as 'the funny bone'. Striking this nerve can
cause a tingling sensation ("funny" feeling), and sometimes a
significant amount of pain. It lies anteriorly to the medial epicondyle, and is
easily damaged in elbow injuries.
Cross-section
through the middle of upper arm.
Humerus
Humerus
Human
arm bones diagram
Humerus
- inferior epiphysis. Anterior view.
Humerus
- inferior epiphysis. Posterior view.
Humerus
- superior epiphysis.
Ulna: The
ulna (/ˈʌlnə/[1][2])
or elbow bone is one of the two long bones in the forearm, the other being the
radius. It is prismatic in form and runs parallel to the radius, which is
shorter and smaller. In anatomical position (i.e. when the arms are down at the
sides of the body and the palms of the hands face forward) the ulna is located
at the side of the forearm closest to the body (the medial side), the side of
the little finger.
Upper extremity
Shown is the right hand, palm down
(left) and palm up (right). Ulna is #2
Articulations
The
ulna articulates with:
·
trochlea of the humerus, at the right
side elbow as a hinge joint with semilunar trochlear notch of the ulna.
·
the radius, near the elbow as a pivot
joint, this allows the radius to cross over the ulna in pronation.
·
the distal radius, where it fits into
the ulna notch.
·
the radius along its length via the
interosseous membrane that forms a syndesmoses joint
·
it is also called the poisidion
Proximal
and distal aspects
The
ulna is broader proximally, and narrower distally.
Proximally,
the ulna has a bony process, the olecranon process, a hook-like structure that
fits into the olecranon fossa of the humerus. This prevents hyperextension and
forms a hinge joint with the trochlea of the humerus. There is also a radial
notch for the head of the radius, and the ulnar tuberosity to which muscles
attach.
At
the distal end of the ulna is a styloid process.
Structure
The
long, narrow medullary cavity is enclosed in a strong wall of compact tissue
which is thickest along the interosseous border and dorsal surface. At the
extremities the compact layer thins. The compact layer is continued onto the
back of the olecranon as a plate of close spongy bone with lamellæ parallel.
From the inner surface of this plate and the compact layer below it
trabeculæ arch forward toward the olecranon and coronoid and cross other
trabeculæ, passing backward over the medullary cavity from the upper part
of the shaft below the coronoid. Below the coronoid process there is a small
area of compact bone from which trabeculæ curve upward to end obliquely
to the surface of the semilunar notch which is coated with a thin layer of
compact bone.
|
Muscle |
Direction |
Attachment |
|
Triceps
brachii muscle |
Insertion |
posterior
part of superior surface of Olecranon process (via common tendon) |
|
Anconeus
muscle |
Insertion |
olecranon
process (lateral aspect) |
|
Brachialis
muscle |
Insertion |
anterior
surface of the coronoid process of the ulna |
|
Pronator
teres muscle |
Origin |
medial
surface on middle portion of coronoid process (also shares origin with medial
epicondyle of the humerus) |
|
Flexor
carpi ulnaris muscle |
Origin |
olecranon
process and posterior surface of ulna (also shares origin with medial
epicondyle of the humerus) |
|
Flexor
digitorum superficialis muscle |
Origin |
coronoid
process (also shares origin with medial epicondyle of the humerus and shaft
of the radius) |
|
Flexor
digitorum profundus muscle |
Origin |
coronoid
process, anteromedial surface of ulna (also shares origin with the
interosseous membrane) |
|
Pronator
quadratus muscle |
Origin |
distal
portion of anterior ulnar shaft |
|
Extensor
carpi ulnaris muscle |
Origin |
posterior
border of ulna (also shares origin with lateral epicondyle of the humerus) |
|
Supinator
muscle |
Origin |
proximal
ulna (also shares origin with lateral epicondyle of the humerus) |
|
Abductor
pollicis longus muscle |
Origin |
posterior
surface of ulna (also shares origin with the posterior surface of the radius
bone) |
|
Extensor
pollicis longus muscle |
Origin |
dorsal
shaft of ulna (also shares origin with the dorsal shaft of the radius and the
interosseous membrane) |
|
Extensor
pollicis brevis muscle |
Origin |
dorsal
shaft of ulna (also shares origin with the dorsal shaft of the radius and the
interosseous membrane) |
|
Extensor
indicis muscle |
Origin |
posterior
surface of distal ulna (also shares origin with the interosseous membrane) |
Fracture
Specific
fracture types of the ulna include:
Monteggia
fracture - a fracture of the proximal third of the ulna with the dislocation of
the head of the radius
Hume
fracture - a fracture of the olecranon with an associated anterior dislocation
of the radial head
Radius (bone): he
radius or radial bone is one of the two large bones of the forearm, the other being
the ulna. It extends from the lateral side of the elbow to the thumb side of
the wrist and runs parallel to the ulna, which exceeds it in length and size.
It is a long bone, prism-shaped and slightly curved longitudinally. The radius
articulates with the capitulum of the humerus, the radial notch and the head of
the ulna. The corresponding bone in the lower leg is the tibia.
The
word radius is Latin for "ray". In the context of the radius bone, a
ray can be thought of rotating around an axis line extending diagonally from
center of capitulum to the center of distal ulna. While the ulna is the major
contributor to the elbow joint, the radius primarily contributes to the wrist
joint.
The
radius is named so because the radius (bone) acts like the radius (of a
circle). The ulna acts as the center point to the circle because when the arm
is rotated the ulna does not move. The radius (bone) acts like the radius (of a
circle) because it rotates around the ulna and the far end (where it joins to
the bones of the hand), known as the styloid process of the radius, is the
distance from the ulna (center of the circle) to the edge of the radius (the
circle).
Shape
The
radius has a body and two extremities. The upper extremity of the radius
consists of a somewhat cylindrical head articulating with the ulna and the
humerus, a neck, and a double tuberosity. The body of the radius is
self-explanatory, and the lower extremity of the radius is roughly quadrilateral
in shape, with articular surfaces for the ulna, scaphoid and lunate bones. The
distal end of the radius forms a palpable point called the styloid process.
Along with the proximal and distal radioulnar articulations, an interosseous
membrane originates medially along the length of the body of the radius to
attach the radius to the ulna.
Muscle
attachments
The
biceps muscle inserts on the radial tuberosity of the upper extremity of the
bone. The upper third of the body of the bone attaches to the supinator, the
flexor digitorum superficialis, and the flexor pollicis longus muscles. The
middle third of the body attaches to the extensor ossis metacarpi pollicis,
extensor primi internodii pollicis, and the pronator teres muscles. The lower
quarter of the body attaches to the pronator quadratus muscle and the tendon of
the supinator longus.
Structure
The
long narrow medullary cavity is enclosed in a strong wall of compact bone. It
is thickest along the interosseous border and thinnest at the extremities, save
over the cup-shaped articular surface (fovea) of the head.
The
trabeculae of the spongy tissue are somewhat arched at the upper end and pass
upward from the compact layer of the shaft to the fovea capituli (the humerus's
cup-shaped articulatory notch); they are crossed by others parallel to the
surface of the fovea. The arrangement at the lower end is somewhat similar. It
is missing in radial aplasia.
Fracture
A
subtle radial head fracture with associated positive sail sign
Radius,
styloid process - anterior view
Radius,
ulnar noch - posterior veiw
Specific
fracture types of the radius include:
Essex-Lopresti
fracture - a fracture of the radial head with concomitant dislocation of the
distal radio-ulnar joint with disruption of the interosseous membrane.[3]
Distal
radius fracture
Galeazzi
fracture - a fracture of the radius with dislocation of the distal radioulnar
joint
Colles'
fracture - a distal fracture of the radius with dorsal (posterior) displacement
of the wrist and hand
Smith's
fracture - a distal fracture of the radius with volar (ventral) displacement of
the wrist and hand
Barton's
fracture - an intra-articular fracture of the distal radius with dislocation of
the radiocarpal joint.
3)
Hands (54 bones) - Left and right Carpal (16) (wrist), Metacarpal (10),
Proximal phalanges (10), Middle phalanges (8), distal phalanges (10).
Carpal: In human anatomy, the carpal bones can be
classified as belonging to two transverse rows or three longitudinal columns.
Micro-radiography
of 8 weeks human embryo hand
Ligaments
Ligaments
of the wrist
There
are four groups of ligaments in the region of the wrist:
1.
The ligaments of the wrist proper
which unite the ulna and radius with the carpus: the ulnar and radial
collateral ligaments; the palmar and dorsal radiocarpal ligaments; and the
palmar ulnocarpal ligament.
2.
The ligaments of the intercarpal
articulations which unite the carpal bones with one another: the radiate carpal
ligament; the dorsal, palmar, and interosseous intercarpal ligaments; and the
pisohamate ligament,
3.
The ligaments of the carpometacarpal
articulations which unite the carpal bones with the metacarpal bones: the
pisometacarpal ligament and the palmar and dorsal carpometacarpal ligaments
4.
The ligaments of the intermetacarpal
articulations which unite the metacarpal bones: the dorsal, interosseous, and
palmar metacarpal ligaments
The
pair of rows together form an arch which is convex proximally and concave
distally. On the palmar side, the carpus is concave, forming the carpal tunnel
which is covered by the flexor retinaculum.
Because the proximal row is simultaneously related to the articular
surfaces of the radius and the distal row, it adapts constantly to these mobile
surfaces. The bones of this row - scaphoid, lunate, and triquetrum - have their
individual movements. The scaphoid contributes to the stability of the
midcarpus as it articulates distally with the trapezium and the trapezoid. The
distal row is more rigid as its transverse arch moves with the metacarpals.
Biomechanically
and clinically, the carpal bones are better understood as arranged in three
longitudinal columns:
A
radial scaphoid column consisting of the scaphoideum, trapezium, and
trapezoideum
A
lunate column consisting of the lunate and capitate
A
ulnar triquetral column consisting of the triquetrum and hamatum.
In
this context the pisiform is regarded as a sesamoid bone embedded in the tendon
of the flexor carpi ulnaris. The ulnar column leaves a gap between the ulna and
the triquetrum, and therefore, only the radial or scaphoid and central or
capitate columns articulate with the radius. The wrist is more stable in
flexion than in extension more because of the strength of various capsules and
ligaments than the interlocking parts of the skeleton.
Movements
The
hand is said to be in straight position when the third finger runs over the
capitate bone and is in a straight line with the forearm. This should not be
confused with the midposition of the hand which corresponds to an ulnar
deviation of 12 degrees. From the straight position two pairs of movements of
the hand are possible: abduction (movement towards the radius, so called radial
deviation or abduction) of 15 degrees and adduction (movement towards the ulna,
so called ulnar deviation or adduction) of 40 degrees when the arm is in strict
supination and slightly greater in strict pronation. Flexion (tilting towards
the palm, so called palmar flexion) and extension (tilting towards the back of
the hand, so called dorsiflexion) is possible with a total range of 170
degrees.
Radial
abduction/ulnar adduction
During
radial abduction the scaphoid is tilted towards the palmar side which allows
the trapezium and trapezoid to approach the radius. Because the trapezoid is
rigidly attached to the second metacarpal bone to which also the flexor carpi
radialis and extensor carpi radialis are attached, radial abduction effectively
pulls this combined structure towards the radius. During radial abduction the
pisiform traverses the greatest path of all carpal bones. Radial abduction is
produced by (in order of importance) extensor carpi radialis longus, abductor
pollicis longus, extensor pollicis longus, flexor carpi radialis, and flexor
pollicis longus.
Ulnar
adduction causes a tilting or dorsal shifting of the proximal row of carpal
bones. It is produced by extensor carpi ulnaris, flexor carpi ulnaris, extensor
digitorum, and extensor digiti minimi.
Both
radial abduction and ulnar adduction occurs around a dorsopalmar axis running
through the head of the capitate bone.
Palmar
flexion/dorsiflexion
During
palmar flexion the proximal carpal bones are displaced towards the dorsal side
and towards the palmar side during dorsiflexion. While flexion and extension
consist of movements around a pair of transverse axes — passing through the
lunate bone for the proximal row and through the capitate bone for the distal
row — palmar flexion occurs mainly in the radiocarpal joint and dorsiflexion in
the midcarpal joint.
Dorsiflexion
is produced by (in order of importance) extensor digitorum, extensor carpi
radialis longus, extensor carpi radialis brevis, extensor indicis, extensor
pollicis longus, and extensor digiti minimi. Palmar flexion is produced by (in
order of importance) flexor digitorum superficialis, flexor digitorum
profundus, flexor carpi ulnaris, flexor pollicis longus, flexor carpi radialis,
and abductor pollicis longus.
Combined
movements
Combined
with movements in both the elbow and shoulder joints, intermediate or combined
movements in the wrist approximate those of a ball-and-socket joint with some
necessary restrictions, such as maximum palmar flexion blocking abduction.
Accessory
movements
Anteroposterior
gliding movements between adjacent carpal bones or along the midcarpal joint
can be achieved by stabilizing individual bones while moving another (i.e.
gripping the bone between the thumb and index finger).
Individual
bone
Posterior
and anterior view of a human carpus
Almost
all carpals (except the pisiform) have six surfaces. Of these the palmar or
anterior and the dorsal or posterior surfaces are rough, for ligamentous
attachment; the dorsal surfaces being the broader, except in the lunate.
The
superior or proximal, and inferior or distal surfaces are articular, the
superior generally convex, the inferior concave; the medial and lateral
surfaces are also articular where they are in contact with contiguous bones,
otherwise they are rough and tuberculated.
Metacarpal: In human anatomy, the metacarpus is the
intermediate part of the hand skeleton that is located between the phalanges
(bones of the fingers) and the carpus which forms the connection to the
forearm. The metacarpus consists of metacarpal bones. Its equivalent in the
foot is the metatarsus.
The
five metacarpal bones, numbered. (Left hand shown with thumb on right.)
Multiple
fractures of the metacarpals (aka broken hand). (Right hand shown with thumb on
left.)
Human
anatomy
The
metacarpals form a transverse arch to which the rigid row of distal carpal
bones are fixed. The peripheral metacarpals (those of the thumb and little
finger) form the sides of the cup of the palmar gutter and as they are brought
together they deepen this concavity. The index metacarpal is the most firmly
fixed, while the thumb metacarpal articulates with the trapezium and acts
independently from the others. The middle metacarpals are tightly united to the
carpus by intrinsic interlocking bone elements at their bases. The ring
metacarpal forms a transitional element of the semi-independent last
metacarpal.
Each
metacarpal bone consists of a body and two extremities.
Body
The
body (corpus; shaft) is prismoid in form, and curved, so as to be convex in the
longitudinal direction behind, concave in front. It presents three surfaces:
medial, lateral, and dorsal.
The
medial and lateral surfaces are concave, for the attachment of the interosseus
muscles, and separated from one another by a prominent anterior ridge.
The
dorsal surface presents in its distal two-thirds a smooth, triangular,
flattened area which is covered in by the tendons of the extensor muscles. This
surface is bounded by two lines, which commence in small tubercles situated on
either side of the digital extremity, and, passing upward, converge and meet
some distance above the center of the bone and form a ridge which runs along
the rest of the dorsal surface to the carpal extremity. This ridge separates
two sloping surfaces for the attachment of the interossei dorsales.
To
the tubercles on the digital extremities are attached the collateral ligaments
of the metacarpophalangeal joints.
Base
The
base or carpal extremity (basis) is of a cuboidal form, and broader behind than
in front: it articulates with the carpus, and with the adjoining metacarpal
bones; its dorsal and volar surfaces are rough, for the attachment of
ligaments.
Head
The
head or digital extremity (capitulum) presents an oblong surface markedly
convex from before backward, less so transversely, and flattened from side to
side; it articulates with the proximal phalanx. It is broader, and extends
farther upward, on the volar than on the dorsal aspect, and is longer in the
antero-posterior than in the transverse diameter. On either side of the head is
a tubercle for the attachment of the collateral ligament of the
metacarpophalangeal joint.
The
dorsal surface, broad and flat, supports the tendons of the extensor muscles.
The
volar surface is grooved in the middle line for the passage of the flexor
tendons, and marked on either side by an articular eminence continuous with the
terminal articular surface.
Articulations
Besides
the metacarpophalangeal joints, the metacarpal bones articulate by
carpometacarpal joints as follows:
the
first with the trapezium;
the
second with the trapezium, trapezoid, capitate and third metacarpal;
the
third with the capitate and second and fourth metacarpals;
the
fourth with the capitate, hamate, and third and fifth metacarpals;
and
the fifth with the hamate and fourth metacarpal.
Insertions
Extensor
Extensor
Abductor
Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts
thumb in frontal plane; extends thumb at carpometacarpal joint
Opponens
Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to
the fingertips
Opponens
digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal
V at carpometacarpal joint when little finger is moved into opposition with tip
of thumb; deepens palm of hand.
Congenital
disorders
The
fourth and fifth metacarpal bones are commonly "blunted" or
shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.
A
blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner
syndrome.
Blunted
metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal
cell carcinoma syndrome.
Fracture
The
neck of a metacarpal (in the transition between the body and the head) is a
common location for a boxer's fracture.
Metacarpals
of left hand, anterior aspect
Metacarpals
of left hand, medial aspect
First
metacarpal bone (left)
Second
metacarpal bone (left)
Third
metacarpal bone (left)
Fourth
metacarpal bone (left)
Fifth
metacarpal bone (left)
4)
Pelvis (2 bones) - Left and right os coxae (2) (ilium).
Pelvis: In human anatomy, the pelvis (plural pelves or pelvises,
sometimes also called pelvic region of the trunk) is the lower part of the
trunk, between the abdomen and the lower limbs (legs).[1] The pelvis includes
several structures:[1]
the
bony pelvis, or pelvic skeleton, the part of the skeleton connecting the sacrum
region of the spine to the femurs, subdivided into:
·
the pelvic girdle (the two hip bones,
which are part of the appendicular skeleton) and
·
the pelvic region of the spine
(sacrum, and coccyx, which are part of the axial skeleton)
·
the pelvic cavity, typically defined
as a small part of the space enclosed by the pelvic skeleton, delimited by the
pelvic brim above and the pelvic floor below; alternatively, the pelvic cavity
is sometimes also defined as the whole space enclosed by the pelvic skeleton,
subdivided into:
1.
the greater or false pelvis, above
the pelvic brim
2.
the lesser or true pelvis, below the
pelvic brim
3.
the pelvic floor or pelvic diaphragm,
below the pelvic cavity
4.
the perineum, below the pelvic
diaphragm
In
the human, the pelvic skeleton is formed in the area of the back (posterior
dorsal), by the sacrum and the coccyx (the caudal portion of the axial
skeleton), and laterally and anteriorly (forward and to the side), by a pair of
hip bones, the lower extremity, (parts of the appendicular skeleton). In an
adult human being, the pelvic skeleton is thus composed of three large bones,
and the coccyx (3–5 bones); however, before puberty, each hip bone consists of
three discrete (separate) bones — the ilium, ischium, pubis — that have yet to
fuse at adulthood; thus, in puberty, the human pelvic skeleton can comprise
more than 10 bones, depending upon the
composition of the person’s coccyx.
Female
type pelvis
Male
type pelvis
Brief
description
The
bony pelvis (or pelvic skeleton) is the section between the legs and the torso
that connects the spine (backbone) to the thigh bones. In adults, it is mainly
constructed of two hip bones, one on the right and one on the left of the body.
The two hip bones are each made up of 3 sections, the
The
gap enclosed by the pelvic skeleton, called the pelvic cavity, is the section
of the body underneath the abdomen and mainly consists of the reproductive
organs (sex organs) and the rectum.
Bony
pelvis
1.
Sacrum
2.
3. Ischium
4. Pubic bone
5. Pubic symphysis
6. Acetabulum
7. Obturator foramen
8. Coccyx
Red line: Terminal line/pelvic brim
Functions
The
skeleton of the pelvis is a basin-shaped ring of bones connecting the vertebral
column to the femora.
Its
primary functions are to bear the weight of the upper body when sitting and
standing; transfer that weight from the axial skeleton to the lower
appendicular skeleton when standing and walking; and provide attachments for
and withstand the forces of the powerful muscles of locomotion and posture.
Compared to the shoulder girdle, the pelvic girdle is thus strong and rigid.
Its
secondary functions are to contain and protect the pelvic and abdominopelvic
viscera (inferior parts of the urinary tracts, internal reproductive organs);
provide attachment for external reproductive organs and associated muscles and
membranes.
As
a mechanical structure
The
pelvic girdle consists of the two hip bones. The hip bones are connected to
each other anteriorly at the pubic symphysis, and posteriorly to the sacrum at
the sacroiliac joints to form the pelvic ring. The ring is very stable and
allows very little mobility, a prerequisite for transmitting loads from the
trunk to the lower limbs.
As
a mechanical structure the pelvis may be thought of as four roughly triangular
and twisted rings. Each superior ring is formed by the iliac bone; the anterior
side stretches from the acetabulum up to the anterior superior iliac spine; the
posterior side reaches from the top of the acetabulum to the sacroiliac joint;
and the third side is formed by the palpable iliac crest. The lower ring,
formed by the rami of the pubic and ischial bones, supports the acetabulum and
is twisted 80-90 degrees in relation to the superior ring.
An
alternative approach is to consider the pelvis part of an integrated mechanical
system based on the tensegrity icosahedron as an infinite element. Such a
system is able to withstand omnidirectional forces — ranging from weight-bearing
to childbearing — and, as a low energy requiring system, is favoured by natural
selection.
The
pelvic inclination angle is the single most important element of the human body
posture and is adjusted at the hips. It is also one of the rare things that can
be measured at the assessment of the posture. A simple method of measurement
was described by the British orthopedist Philip Willes and is performed by
using an inclinometer.
Junctions
Coronal
section through pubic symphysis
The
two hip bones are joined anteriorly at the pubic symphysis by a fibrous
cartilage covered by a hyaline cartilage, the interpubic disk, within which a
non-synovial cavity might be present. Two ligaments, the superior and inferior
pubic ligaments, reinforce the symphysis.
Both
sacroiliac joints, formed between the auricular surfaces of the sacrum and the
two hip bones. are amphiarthroses, almost immobile joints enclosed by very taut
joint capsules. This capsule is strengthened by the ventral, interosseous, and
dorsal sacroiliac ligaments. The most important accessory ligaments of the
sacroiliac joint are the sacrospinous and sacrotuberous ligaments which
stabilize the hip bone on the sacrum and prevent the promonotory from tilting
forward. Additionally, these two ligaments transform the greater and lesser
sciatic notches into the greater and lesser foramina, a pair of important
pelvic openings. The iliolumbar ligament is a strong ligament which connects
the tip of the transverse process of the fifth lumbar vertebra to the posterior
part of the inner lip of the iliac crest. It can be thought of as the lower
border of the thoracolumbar fascia and is occasionally accompanied by a smaller
ligamentous band passing between the fourth lumbar vertebra and the iliac
crest. The lateral lumbosacral ligament is partly continuous with the
iliolumbar ligament. It passes between the transverse process of the fifth
vertebra to the ala of the sacrum where it intermingle with the anterior
sacroiliac ligament.
The
joint between the sacrum and the coccyx, the sacrococcygeal symphysis, is
strengthened by a series of ligaments. The anterior sacrococcygeal ligament is
an extension of the anterior longitudinal ligament (ALL) that run down the
anterior side of the vertebral bodies. Its irregular fibers blend with the
periosteum. The posterior sacrococcygeal ligament has a deep and a superficial
part, the former is a flat band corresponding to the posterior longitudinal
ligament (PLL) and the latter corresponds to the ligamenta flava. Several other
ligaments complete the foramen of the last sacral nerve.
Articulations
The
lumbosacral joint, between the sacrum and the last lumbar vertebra, has, like
all vertebal joints, an intervertebral disc, anterior and posterior ligaments,
ligamenta flava, interspinous and supraspinous ligaments, and synovial joints
between the articular processes of the two bones. In addition to these
ligaments the joint is strengthened by the iliolumbar and lateral lumbosacral
ligaments. The iliolumbar ligament passes between the tip of the transverse
process of the fifth lumbar vertebra and the posterior part of the iliac crest.
The lateral lumbosacral ligament, partly continuous with the iliolumbar
ligament, passes down from the lower border of the transverse process of the
fifth vertebra to the ala of the sacrum. The movements possible in the
lumbosacral joint are flexion and extension, a small amount of lateral flexion
(from 7 degrees in childhood to 1 degree in adults), but no axial rotation.
Between ages 2–13 the joint is responsible for as much as 75% (about 18
degrees) of flexion and extension in the lumbar spine. From age 35 the
ligaments considerably limit the range of motions.
The
three extracapsular ligaments of the hip joint — the iliofemoral,
ischiofemoral, and pubofemoral ligaments — form a twisting mechanism encircling
the neck of the femur. When sitting, with the hip joint flexed, these ligaments
become lax permitting a high degree of mobility in the joint. When standing,
with the hip joint extended, the ligaments get twisted around the femoral neck,
pushing the head of the femur firmly into the acetabulum, thus stabilising the
joint. The zona orbicularis assists in maintaining the contact in the joint by
acting like a buttonhole on the femoral head. The intracapsular ligament, the
ligamentum teres, transmits blood vessels that nourish the femoral head.
Pelvic
cavity
Main
article: Pelvic cavity
The
pelvic cavity is a body cavity that is bounded by the bones of the pelvis and which
primarily contains reproductive organs and the rectum.
A
distinction is made between the lesser or true pelvis inferior to the terminal
line, and the greater or false pelvis above it. The pelvic inlet or superior
pelvic aperture, which leads into the lesser pelvis, is bordered by the
promontory, the arcuate line of ilium, the iliopubic eminence, the pecten of
the pubis, and the upper part of the pubic symphysis. The pelvic outlet or
inferior pelvic aperture is the region between the subpubic angle or pubic
arch, the ischial tuberosities and the coccyx.
Ligaments:
obturator membrane, inguinal ligament (lacunar ligament, iliopectineal arch)
Development
Each
side of the pelvis is formed as cartilage, which ossifies as three main bones
which stay separate through childhood: ilium, ischium, pubis. At birth the
whole of the hip joint (the acetabulum area and the top of the femur) is still
made of cartilage (but there may be a small piece of bone in the great
trochanter of the femur); this makes it difficult to detect congenital hip
dislocation by X-raying.
Muscles
Shoulder
and intrinsic back
Intrinsic
back muscles
The
inferior parts of latissimus dorsi, one of the muscles of the upper limb,
arises from the posterior third of the iliac crest. Its action on the shoulder
joint are internal rotation, adduction, and retroversion. It also contributes
to respiration (i.e. coughing). When the arm is adducted, latissimus dorsi can
pull it backward and medially until the back of the hand covers the buttocks.
In
a longitudinal osteofibrous canal on either side of the spine there is a group
of muscles called the erector spinae which is subdivided into a lateral
superficial and a medial deep tract. In the lateral tract, the iliocostalis
lumborum and longissimus thoracis originates on the back of the sacrum and the
posterior part of the iliac crest. Contracting these muscles bilaterally
extends the spine and unilaterally contraction bends the spine to the same
side. The medial tract has a "straight" (interspinales, intertransversarii,
and spinalis) and an "oblique" (multifidus and semispinalis)
component, both of which stretch between vertebral processes; the former acts
similar to the muscles of the lateral tract, while the latter function
unilaterally as spine extensors and bilaterally as spine rotators. In the
medial tract, the multifidi originates on the sacrum.
Abdomen
The
muscles of the abdominal wall are subdivided into a superficial and a deep
group.
The
superficial group is subdivided into a lateral and a medial group. In the
medial superficial group, on both sides of the centre of the abdominal wall
(the linea alba), the rectus abdominis stretches from the cartilages of ribs
V-VII and the sternum down to the pubic crest. At the lower end of the rectus
abdominis, the pyramidalis tenses the linea alba. The lateral superficial
muscles, the transversus and external and internal oblique muscles, originate
on the rib cage and on the pelvis (iliac crest and inguinal ligament) and are
attached to the anterior and posterior layers of the sheath of the rectus.
Flexing
the trunk (bending forward) is essentially a movement of the rectus muscles,
while lateral flexion (bending sideways) is achieved by contracting the
obliques together with the quadratus lumborum and intrinsic back muscles.
Lateral rotation (rotating either the trunk or the pelvis sideways) is achieved
by contracting the internal oblique on one side and the external oblique on the
other. The transversus' main function is to produce abdominal pressure in order
to constrict the abdominal cavity and pull the diaphragm upward.
There
are two muscles in the deep or posterior group. Quadratus lumborum arises from
the posterior part of the iliac crest and extends to the rib XII and lumbar
vertebrae I-IV. It unilaterally bends the trunk to the side and bilaterally
pulls the 12th rib down and assists in expiration. The iliopsoas consists of
psoas major (and occasionally psoas minor) and iliacus, muscles with separate
origins but a common insertion on the lesser trochanter of the femur. Of these,
only iliacus is attached to the pelvis (the iliac fossa). However, psoas passes
through the pelvis and because it acts on two joints, it is topographically
classified as a posterior abdominal muscle but functionally as a hip muscle.
Iliopsoas flexes and externally rotates the hip joints, while unilateral
contraction bends the trunk laterally and bilateral contraction raises the
trunk from the supine position.
Pelvic
floor
Perineum
The
pelvic floor has two inherently conflicting functions: One is to close the
pelvic and abdominal cavities and bear the load of the visceral organs, the
other is to control the openings of the rectum and urogenital organs that
pierce the pelvic floor and make it weaker. To achieve both these tasks, the
pelvic floor is composed of several overlapping sheets of muscles and
connective tissues.
The
pelvic diaphragm is composed of the levator ani and the coccygeus muscle. These
arise between the symphysis and the ischial spine and converge on the coccyx
and the anococcygeal ligament which spans between the tip of the coccyx and the
anal hiatus. This leaves a slit for the anal and urogenital openings. Because
of the width of the genital aperture, which is wider in females, a second
closing mechanism is required. The urogenital diaphragm consists mainly of the
deep transverse perineal which arises from the inferior ischial and pubic rami
and extends to the urogential hiatus. The urogenital diaphragm is reinforced posteriorly
by the superficial transverse perineal.
The
external anal and urethral sphincters close the anus and the urethra. The
former is surrounded by the bulbospongiosus which narrows the vaginal introitus
in females and surrounds the corpus spongiosum in males. Ischiocavernosus
squeezes blood into the corpus cavernosum penis and clitoridis.
Hip
and thigh
Muscles
of the hip
The
muscles of the hip are divided into a dorsal and a ventral group.
The
dorsal hip muscles are either inserted into the region of the lesser trochanter
(anterior or inner group) or the greater trochanter (posterior or outer group).
Anteriorly, the psoas major (and occasionally psoas minor) originates along the
spine between the rib cage and pelvis. The iliacus originates on the iliac
fossa to join psoas at the iliopubic eminence to form the iliopsoas which is
inserted into the lesser trochanter. The iliopsoas is the most powerful hip
flexor.
The
posterior group includes the gluteii maximus, medius, and minimus. Maximus has
a wide origin stretching from the posterior part of the iliac crest and along
the sacrum and coccyx, and has two separate insertions: a proximal which
radiates into the iliotibial tract and a distal which inserts into the gluteal
tuberosity on the posterior side of the femoral shaft. It is primarily an
extensor and lateral rotator of the hip joint, but, because of its bipartite
insertion, it can both adduct and abduct the hip. Medius and minimus arise on
the external surface of the ilium and are both inserted into the greater
trochanter. Their anterior fibers are medial rotators and flexors while the
posterior fibers are lateral rotators and extensors. The piriformis has its
origin on the ventral side of the sacrum and is inserted on the greater
trochanter. It abducts and laterally rotates the hip in the upright posture and
assists in extension of the thigh. The tensor fasciae latae arises on the
anterior superior iliac spine and inserts into the iliotibial tract. It presses
the head of the femur into the acetabulum and flexes, medially rotates, and
abducts the hip.
The
ventral hip muscles are important in the control of the body's balance. The
internal and external obturator muscles together with the quadratus femoris are
lateral rotators of the hip. Together they are stronger than the medial
rotators and therefore the feet point outward in the normal position to achieve
a better support. The obturators have their origins on either sides of the
obturator foramen and are inserted into the trochanteric fossa on the femur.
Quadratus arises on the ischial tuberosity and is inserted into the
intertrochanteric crest. The superior and inferior gemelli, arising from the
ischial spine and ischial tuberosity respectively, can be thought of as
marginal heads of the obturator internus, and their main function is to assist
this muscle.
Anterior
thigh muscles
Posterior
thigh muscles
The
muscles of the thigh can be subdivided into adductors (medial group), extensors
(anterior group), and flexors (posterior group). The extensors and flexors act
on the knee joint, while the adductors mainly act on the hip joint.
The
thigh adductors have their origins on the inferior ramus of the pubic bone and
are, with the exception of gracilis, inserted along the femoral shaft. Together
with sartorius and semitendinosus, gracilis reaches beyond the knee to their
common insertion on the tibia.
The
anterior thigh muscles form the quadriceps which is inserted on the patella
with a common tendon. Three of the four muscles have their origins on the
femur, while rectus femoris arises from the anterior inferior iliac spine and
is thus the only of the four acting on two joints.
The
posterior thigh muscles have their origins on the inferior ischial ramus, with
the exception of the short head of the biceps femoris. The semitendinosus and
semimembranosus are inserted on the tibia on the medial side of the knee, while
biceps femoris is inserted on the fibula, on the knee's lateral side.
Pregnancy
and childbirth
In
later stages of pregnancy the fetus's head aligns inside the pelvis. Also
joints of bones soften due to the effect of pregnancy hormones. These factors
may cause pelvic joint pain (Symphysis Pubis Dysfunction or SPD). As the end of
pregnancy approaches, the ligaments of the sacroiliac joint loosen, letting the
pelvis outlet widen somewhat; this is easily noticeable in the cow.
During
childbirth (unless by Cesarean section) the fetus passes through the maternal
pelvic opening.
Sexual
dimorphism
Modern
humans are to a large extent characterized by bipedal locomotion and large
brains. Because the pelvis is vital to both locomotion and childbirth, natural
selection has been confronted by two conflicting demands: a wide birth canal
and locomotion efficiency, a conflict referred to as the "obstetrical
dilemma". The female pelvis has evolved to its maximum width for
childbirth — a wider pelvis would make women unable to walk. In contrast, human
male pelves are not constrained by the need to give birth and therefore are
optimized for bipedal locomotion.
The
principal differences between male and female true and false pelvis include:
The
female pelvis is larger and broader than the male pelvis which is taller,
narrower, and more compact.
The
female inlet is larger and oval in shape, while the male sacral promontory
projects further (i.e. the male inlet is more heart-shaped).
The
sides of the male pelvis converge from the inlet to the outlet, whereas the
sides of the female pelvis are wider apart.
The
angle between the inferior pubic rami is acute (70 degrees) in men, but obtuse
(90-100 degrees) in women. Accordingly, the angle is called subpubic angle in
men and pubic arch in women. Additionally, the bones forming the angle/arch are
more concave in females but straight in males.
The
distance between the ischia bones is small in males, making the outlet narrow,
but large in females, who have a relatively large outlet. The ischial spines
and tuberosities are heavier and project farther into the pelvic cavity in
males. The greater sciatic notch is wider in females.
The
iliac crests are higher and more pronounced in males, making the male false
pelvis deeper and more narrow than in females.
The
male sacrum is long, narrow, more straight, and has a pronounced sacral
promontory. The female sacrum is shorter, wider, more curved posteriorly, and
has a less pronounced promontory.
The
acetabula are wider apart in females than in males. In males, the acetabulum
faces more laterally, while it faces more anteriorly in females. Consequently,
when men walk the leg can move forwards and backwards in a single plane. In
women, the leg must swing forward and inward, from where the pivoting head of
the femur moves the leg back in another plane. This change in the angle of the
femoral head gives the female gait its characteristic (i.e. swinging of hips).
See
also: Sex differences in humans
Caldwell-Moloy
classification
Throughout
the 20th century pelvimetric measurements were made on pregnant women to
determine whether a natural birth would be possible, a practice today limited
to cases where a specific problem is suspected or following a caesarean
delivery. William Edgar Caldwell and Howard Carmen Moloy studied collections of
skeletal pelves and thousands of stereoscopic radiograms and finally recognized
three types of female pelves plus the masculine type. In 1933 and 1934 they
published their typology, including the Greek names since then frequently
quoted in various handbooks: Gynaecoid (gyne, woman), anthropoid (anthropos,
human being), platypelloid (platys, flat), and android (aner, man).
The
gynaecoid pelvis is the so-called normal female pelvis. Its inlet is either
slightly oval, with a greater transverse diameter, or round. The interior walls
are straight, the subpubic arch wide, the sacrum shows an average to backward
inclination, and the greater sciatic notch is well rounded. Because this type
is spacious and well proportioned there is little or no difficulty in the birth
process. Caldwell and his co-workers found gynaecoid pelves in about 50 per
cent of specimens.
The
platypelloid pelvis has a transversally wide, flattened shape, is wide
anteriorly, greater sciatic notches of male type, and has a short sacrum that
curves inwards reducing the diameters of the lower pelvis. This is similar to
the rachitic pelvis where the softened bones widen laterally because of the
weight from the upper body resulting in a reduced anteroposterior diameter.
Giving birth with this type of pelvis is associated with problems, such as
transverse arrest. Less than 3 per cent of women have this pelvis type.
The
android pelvis is a female pelvis with masculine features, including a wedge or
heart shaped inlet caused by a prominent sacrum and a triangular anterior
segment. The reduced pelvis outlet often causes problems during child birth. In
1939
The
anthropoid pelvis is characterized by an oval shape with a greater
anteroposterior diameter. It has straight walls, a small subpubic arch, and
large sacrosciatic notches. The sciatic spines are placed widely apart and the
sacrum is usually straight resulting in deep non-obstructed pelvis.
However,
Caldwell and Moloy then complicated this simple fourfold scheme by dividing the
pelvic inlet into posterior and anterior segments. They named a pelvis
according to the anterior segment and affixed another type according to the
character of the posterior segment (i.e. anthropoid-android) and ended up with
no less than 14 morphologies. Notwithstanding the popularity of this simple
classification, the pelvis is much more complicated than this as the pelvis can
have different dimensions at various levels of the birth canal.
Caldwell
and Moloy also classified the physique of women according to their types of
pelves: the gynaecoid type has small shoulders, a small waist and wide hips;
the android type looks square-shaped from behind; and the anthropoid type has
wide shoulders and narrow hips. Lastly, in their article they described all
non-gynaecoid or "mixed" types of pelves as "abnormal", a
word which has stuck in the medical world even though at least 50 per cent of
women have these "abnormal" pelves.
The
classification of Caldwell and Moloy was influenced by earlier classifications
attempting to define the ideal female pelvis, treating any deviations from this
ideal as dysfunctions and the cause of obstructed labour. In the 19th century
anthropologists and others saw an evolutionary scheme in these pelvic
typologies, a scheme since then refuted by archaeology. Since the 1950s
malnutrition is thought to be one of the chief factors affecting pelvic shape
in the
Nowadays
obstetric suitability of the female pelvis is assessed by ultrasound. The
dimensions of the head of the fetus and of the birth canal are accurately
measured and compared, and the feasibility of labor can be predicted.
5)
Thigh and leg (8 bones) - Femur (2) (thigh), Tibia (2), Patella (2) (knee), and
Fibula (2) (leg).
6)
Feet and ankles (52 bones) - Tarsals (14) (ankle), Metatarsals (10), Proximal
phalanges (10), middle phalanges (8), distal phalanges (10).
It
is important to realize that through anatomical variation it is common for the
skeleton to have many extra bones (sutural bones in the skull, cervical ribs,
lumbar ribs and even extra lumbar vertebrae)
The
appendicular skeleton of 126 bones and the axial skeleton of 80 bones together
form the complete skeleton of 206 bones in the human body. Unlike the axial
skeleton, the appendicular skeleton is unfused. This allows for a much greater
range of motion.
Appendicular
skeleton diagram
VIDEO
Muscular system
The muscular system is the
biological system of humans that allows them to move. The muscular system in vertebrates
is controlled through the nervous system, although some muscles (such as
the cardiac
muscle) can be completely autonomous.
Skeletal
muscle structure
Skeletal muscle fibers are
multinucleated, with the cell's nuclei located just beneath the plasma
membrane. The cell is comprised of a series of striped or striated, thread-like
myofibrils.
Within each myofibril there are protein filaments that are anchored by dark Z lines. The fiber is one long continuous thread-like
structure. The smallest cross section of skeletal muscle is called a sarcomere
which is the functional unit within the cell. It extends from one Z line to the
next attached Z line. The individual sarcomere has alternating thick myosin and thin
actin
protein filaments. Myosin forms the center or middle of each sarcomere. The exact
center of the sarcomere is designated the M line. Thinner actin filaments form
a zig zag pattern along the anchor points or Z line.
Upon stimulation by an action potential,
skeletal muscles perform a coordinated contraction by shortening each
sarcomere. The best proposed model for understanding contraction is the sliding filament model of muscle
contraction. Actin and myosin fibers overlap in a contractile motion towards
each other. Myosin filaments have club-shaped heads that project toward the
actin filaments.
Larger structures along the
myosin filament called myosin heads are used to provide attachment points on binding
sites for the actin filaments. The myosin heads move in a coordinated style,
they swivel toward the center of the sarcomere, detach and then reattach to the
nearest active site of the actin filament. This is called a rachet type drive
system. This process consumes large amounts of adenosine triphosphate (ATP).
Energy for this comes from ATP,
the energy source of the cell. ATP binds to the cross bridges between myosin
heads and actin filaments. The release of energy powers the swiveling of the
myosin head. Muscles store little ATP and so must continuously recycle the
discharged adenosine diphosphate molecule (ADP) into
ATP rapidly. Muscle tissue also contains a stored supply of a fast acting
recharge chemical, creatine phosphate which can assist initially
producing the rapid regeneration of ADP into ATP.
Calcium ions
are required for each cycle of the sarcomere. Calcium is released from the sarcoplasmic reticulum into the sarcomere
when a muscle is stimulated to contract. This calcium uncovers the actin
binding sites. When the muscle no longer needs to contract, the calcium ions
are pumped from the sarcomere and back into storage in the sarcoplasmic reticulum.
Control of
muscle contraction
Neuromuscular junctions are the focal
point where a motor neuron attaches to a muscle.
Acetylcholine, (a neurotransmitter used in skeletal muscle
contraction) is released from the axon terminal of the nerve cell when an
action potential reaches the miscoscopic junction, called a synapse.
A group of chemical messengers cross the synapse and stimulate the formation of
electrical changes, which are produced in the muscle cell when the
acetylcholine binds to receptors on its surface. Calcium is released from its
storage area in the cell's sarcoplasmic reticulum. An impulse from a nerve cell
causes calcium release and brings about a single, short muscle contraction called a muscle twitch.
If there is a problem at the neuromuscular junction, a very prolonged
contraction may occur, tetanus. Also, a loss of function at the junction can produce paralysis.
Skeletal muscles are organized
into hundreds of motor units, each of which involves a motor
neuron, attached by a series of thin finger-like structures called axon
terminals. These attach to and control discrete bundles of muscle
fibers. A coordinated and fine tuned response to a specific circumstance will
involve controlling the precise number of motor units used. While individual
muscle units contract as a unit, the entire muscle can contract on a
predetermined basis due to the structure of the motor unit. Motor unit
coordination, balance, and control frequently come under the direction of the cerebellum
of the brain. This allows for complex muscular coordination with little
conscious effort, such as when one drives a car without thinking about the
process.
Muscles
Muscle
activity in an anaerobic vs aerobic environment
Some information
in this article or section has not been verified and may not be reliable.
Please check for inaccuracies,
and modify and cite sources as needed.
At rest, the body produces small
amounts of ATP in an anaerobic production model through glycolysis
in the cytoplasm
of muscle cells. As activity increases to a sustained higher activity level
such as in running, the body can shift to aerobic
ATP production by producing increases in respiratory rate and heart rate. This
allows for a greater supply of oxygen to stimulate aerobic
production of ATP which occurs in the mitochondria.
Once the activity levels decrease, such as occurs at the end of a race, the
body will continue to maintain a short elevated respiratory and heart rate
while the energy borrowed from the bone cells during the transformation to the
aerobic mode is restored. This physiological process is called repayment of oxygen debt.
Once all borrowed substances have been repaid to the muscle cells, the body
will return to homestatic metabolism.
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Bones
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Literature:
1. Адамчик М.В.
Великий англо-український словник. – Київ, 2007.
2. Англійська мова
за професійним спрямуванням: Медицина: навч. посіб. для студ. вищ. навч. закл.
IV рівня акредитації / І. А. Прокоп, В. Я. Рахлецька, Г. Я. Павлишин ; Терноп.
держ. мед. ун-т ім. І. Я. Горбачевського. –
Тернопіль: ТДМУ : Укрмедкнига, 2010. – 576 с.
3. Балла М.І.,
Подвезько М.Л. Англо-український словник. – Київ: Освіта, 2006. – Т. 1,2.
4.
Hansen J. T. Netter’s Anatomy Coloring Book. –
Saunders Elsevier, 2010. – 121 p.
5. Henderson B., Dorsey J. L. Medical Terminology for Dummies. – Willey
Publishing, 2009. – P. 189-211.