Menstrual cycle. Mammary glands
1. Uterine tube structure and functions.
2. Structure of uterus.
3. General description of some cyclic changes in the uterus and ovary. Periods of the menstrual (sexual
cycle).
4. Morphological and functional changes of the
endometrium in the menstrual phase.
5. Histological changes of the endometrium that cause the uterine bleeding.
6. Histophysiology of the endometrium in the
postmenstrual phase.
7. Hormonal adjusting of the cyclic
changes in the uterus.
8. Cyclic changes in the vagina.
9. Development and a general
structure of the mammary gland.
10. Fine structure of the secretory portion of the mammary gland before
lactation.
11. Structural features of the parenchyma of the active
and inactive mammary gland.
10. Description of the secretory process and hormonal regulation of the function of mammary gland.
Female reproductive system includes a lot of organs and all of them are
involved in periodic process, which is known as ovarial-menstrual cycle.
Uterine tubes
The Fallopian tubes, also known as oviducts, uterine
tubes, and salpinges (singular salpinx) are two very
fine tubes of great mobility leading
from the ovaries into the uterus.
Female
genitalia blood supply
There are two Fallopian tubes, attached to either side of the cornual
end of the uterus, and each terminating at or near one ovary forming a
structure called the fimbria. The Fallopian tubes are not
directly attached to the ovaries, but open into the peritoneal cavity
(essentially the inside of the abdomen); they thus form a direct communication
between the peritoneal cavity and the outside via the vagina. In humans, the
Fallopian tubes are about 7–14 cm long.
Fallopian tube has four regions from the ovary to the uterus:
1. Infundibulum -
contains fimbriae (a
fringe of finger-like extensions).
2. Ampulla - usual site of fertilization
3. Isthmus
4. Intramural oviduct
- inside wall of uterus
Oviduct with highly labyrinthine mucosa. Each piece of
folded, branching mucosa is lined with simple columnar epithelium. The rest of
the wall is rather thin and shows interlaced smooth muscle bundles.
.JPG)
Layers of the fallopian tube wall. Muscularis at the top of pointer.
There are three layers of the fallopian tube wall: mucosa (on the left),
muscularis and serosa composed of visceral peritoneum (on the right).
Mucosa has the distinctive
branched folds of the mucosa are the most unusual feature. In cross sections,
the lumen of the ampulla resembles a labyrinth. These folds become smaller in
the segments of the tube that are closer to the uterus. In the intramural
portion, the folds are reduced to small bulges in the lumen, so its internal
surface is almost smooth.
Photomicrograph of part of the wall of an oviduct. The
highly folded mucosa indicates that this region is close to the ovary. PT
stain. Low magnification.
Two layers are present in mucosa: epithelium and lamina propria (loose connective
tissue). The epithelium lining the mucosa is simple columnar and contains two
types of cells: ciliated and secretory ones.
Photomicrograph of the epithelial
lining of an oviduct. The epithelial lining is formed by
ciliated and more darkly staining nonciliated secretory cells. Ciliated cells
contribute to the movement of the oocyte or conceptus to the uterus. PT stain. High magnification.
Scanning electron micrograph of the
lining of an oviduct. Note the abundant cilia. In the
center is the apex of a secretory cell covered by short microvilli. x8000.
A higher power of the fimbriated
(finger-like) end of the oviduct. The surface
epithelium is high cuboidal or low columnar and has a ciliated surface. Arrows
indicate non-ciliated "peg" cells, which are secretory in function
and stand up higher than the other cells.
The cilia beat toward the uterus, causing movement of
the viscous liquid that covers the surface. This liquid consists mainly of
products of the secretory cells interspersed between ciliated cells. This
secretion has nutrient and protective functions for the ovum and promotes
activation (capacitation) of spermatozoa. Movement of the film that covers the
mucosa of the tube, in conjunction with contractions of the muscle layer, helps
to transport the ovum or the conceptus toward the uterus. This movement also
hampers the passage of microorganisms from
uterus to the peritoneal cavity. Transport of the ovum or conceptus to the
uterus, however, is normal in female with immotile cilia syndrome, showing that
ciliary activity is not essential for transport.
The lamina propria of the mucosa
is composed of loose connective tissue and has decidual cells similar to
uterine ones. This makes embryo implantation possible here. In cases of
abnormal nidation (ectopic pregnancy), the lamina propria reacts like the
endometrium, forming numerous decidual cells. Bbecause of its small diameter,
the oviduct cannot contain these new cells and bursts, causing extensive
hemorrhage that can be fatal if not treated immediately.
Muscularis externa consists
of smooth muscular tissue arranged in the inner circular and outer longitudinal
layer.
Outermost tunica serosa
are made up of peritoneum visceral layer (connective
tissue with mesothelium).
The oviduct captures the ovum expelled by the ovary
and carries it toward the uterus. Its lumen is an environment adequate for
fertilization, and its secretions contribute to the nutrition of the embryo
during the early phases of development (tubal period).
At the time of ovulation, the oviduct exhibits active
movement. The fimbria of the infundibulum move closer to the surface of the
ovary, and the funnel shape of the infundibulum facilitates the recovery of the
liberated ovum. The wall of the
oviduct is richly vascularized, and its vessels become dilated at the time of
ovulation. This dilatation gives rigidity and distension to the organ,
facilitating its approximation to the ovary. Fertilization usually takes place
in the lateral third of the oviduct.
The Fallopian tubes are mobile, and have been observed
on time-lapse videography moving about the pelvis. Although
anatomical illustrations have them proceeding from the uterine horns to the ovary, this is not the case for most of the menstrual cycle, and a tube may cross to the other side or lie on top
of the uterus.
Ampular,
isthmic and uterine parts of Fallopian tube
The ostium of the Fallopian tube is the opening in the infundibulum of uterine tube
into the abdominal cavity. In ovulation, the oocyte enters the Fallopian tube through this opening. It is
surrounded by fimbriae, which
help in the collection of the oocyte. In the female reproductive system, the
fimbria (plural, fimbriae) is a fringe of tissue around the ostium of the Fallopian tube, in the direction of the ovary.
An ovary is not directly connected to its adjacent
Fallopian tube. When ovulation is about to occur, the sex hormones activate the fimbriae, causing it to hit the ovary in
a gentle, sweeping motion. An oocyte is released from the ovary into the peritoneal cavity
and the cilia of the fimbriae sweep the ovum into the Fallopian
tube. Not all fimbriae, but only the ovarian
fibria is long enough to reach to ovary.
The third part of the uterine tube is the the infundibulum. It terminates with the ostium of Fallopian tube, surrounded by fimbriae, one of which, the ovarian fimbria is attached to the ovary.
The first part of the uterine tube is the isthmus tubae uterinae.
It is the medial third, and it is constricted.
The ampulla is the
second portion of the uterine tube. It is an intermediate dilated portion, which curves
over the ovary. It is the most common site of human
fertilization
In
a woman's body the tube allows passage of the egg from the ovary to the uterus.
Its different segments are (lateral to medial): the infundibulum with its associated fimbriae near the ovary, the ampullary
region that represents the major portion of the lateral tube, the isthmus
which is the narrower part of the tube that links to the uterus, and the
interstitial (also intramural) part that transverses the uterine musculature.
The tubal ostium is the point where the tubal canal
meets the peritoneal cavity, while the uterine opening of the Fallopian tube is
the entrance into the uterine
cavity, the utero-tubal
junction.
When
an ovum is
developing in an ovary, it is encapsulated in a sac known as an ovarian follicle.
On maturity of the ovum, the follicle and the ovary's wall rupture, allowing
the ovum to escape.
The egg is caught by the fimbriated end and travels to the ampulla where
typically the sperm are met and fertilization
occurs; the fertilized ovum, now a zygote,
travels towards the uterus aided by activity of tubal cilia and activity of the
tubal muscle. After about five days the new embryo enters the
uterine cavity and implants about a day later.
The
release of a mature egg does not alternate between the two ovaries and seems to
be random. After removal of an ovary, the remaining one produces an egg every
month. Occasionally the embryo implants into the Fallopian tube instead of the uterus, creating an
ectopic pregnancy,
commonly known as a "tubal pregnancy".
While
a full testing of tubal functions in patients with infertility
is not possible, testing of tubal patency is important as tubal obstruction
is a major cause of infertility. A hysterosalpingogram, laparoscopy
and dye, or HyCoSy will
demonstrate that tubes are open. Tubal
insufflation is a standard procedure for testing
patency. During surgery the condition of the tubes may be inspected and a dye
such as methylene blue
can be injected into the uterus and shown to pass through the tubes when the
cervix is occluded. As tubal disease is often related to Chlamydia infection,
testing for Chlamydia
antibodies has become a cost-effective
screening device for tubal pathology.
Fallopian tube
Embryos have two
pairs of ducts to let gametes
out of the body; one pair (the Müllerian
ducts) develops in females into the Fallopian tubes,
uterus and vagina, while the
other pair (the Wolffian ducts)
develops in males into the epididymis
and vas deferens.
Normally,
only one of the pairs of tubes will develop while the other regresses and
disappears in utero.
The
homologous organ in the male is the rudimentary appendix testis.
Salpingitis
is inflammation of the Fallopian tubes and may be found alone, or be a
component of pelvic inflammatory disease (PID).
Saccular dilation of the fallopian tube at its narrow portion, due to
inflammation, is known as salpingitis isthmica nodosa. Like PID and endometriosis,
it may lead to Fallopian tube obstruction. Fallopian
tube obstruction is associated with infertility
and ectopic pregnancy.
Fallopian
tube cancer, which typically arises from the epithelial
lining of the Fallopian tube, has historically been considered to be a very
rare malignancy. Recent evidence suggests it probably represents a significant
portion of what has been classified as ovarian
cancer in the past. While tubal cancers may be
misdiagnosed as ovarian cancer, it is of little consequence as the treatment of
both ovarian and Fallopian tube cancer is similar.
The
surgical removal of a Fallopian tube is called a salpingectomy.
To remove both sides is a bilateral salpingectomy. An operation that combines
the removal of a Fallopian tube with removal of at least one ovary is a salpingo-oophorectomy.
An operation to restore a fallopian tube obstruction is called a tuboplasty.
Uterus
The uterus or womb is the major female reproductive organ of most mammals, including humans. One end, the cervix, opens into the vagina; the other is connected on both sides to the fallopian tubes. The term uterus is commonly used within the medical
and related professions, whilst womb is in more common usage.
The bilateral Müllerian ducts form during early fetal life. In males, MIF
secreted from the testes leads to their regression. In females these ducts give
rise to the Fallopian tubes and the uterus. In humans the lower segments of the
two ducts fuse to form a single uterus, however, in cases of uterine
malformations this
development may be disturbed. The different uterine forms in various mammals
are due to various degrees of fusion of the two Müllerian ducts.
Uterus general wiev
The main function of the uterus is to accept a
fertilized ovum which becomes implanted into the endometrium, and
derives nourishment from blood vessels which develop exclusively for this purpose.
The fertilized ovum becomes an embryo, develops into a fetus and gestates until childbirth. Due to anatomical barriers such as the pelvis, the uterus is pushed partially into the abdomen due
to its expansion during pregnancy. Even in pregnancy the mass of a human uterus
amounts to only about a kilogram (
Regions from outside to inside, the path to the uterus is as
follows:
1. Vulva
2. Vagina
3.Cervix uteri -
"neck of uterus"
4. External orifice of the uterus
6. Internal orifice of the uterus
7.
Corpus uteri - "Body of uterus". Cavity of the body of the uterus
Layers from innermost to outermost,
are as follows:
Endometrium. The lining of the uterine cavity is called the
"endometrium." In most mammals, including humans, the endometrium
builds a lining periodically which, if no pregnancy occurs, is shed or
reabsorbed. Shedding of the endometrial lining in humans is responsible for menstrual bleeding (known colloquially as a woman's "period")
throughout the fertile years of a female and for some time beyond. In other
mammals there may be cycles set as widely apart as six months or as frequently
as a few days. Two layers are present in the endomethrium: basal layer lies ower
myomethrium and contains the bottoms of endomethrial glands, which have cambial
cells responsible for regeneration of epithelium; functional
layer is upper changeable layer of uterine wall. Endomethrium has
specific blood supply: basal layer has streight arteries in opposite to coiled
arteries of functional layer. This peculiarity constitute
a lot of in menstrual bleeding.
Myometrium. The uterus mostly consists of smooth muscle, known as "myometrium." Smoth myocytes of
myomethrium are arranged in three layers: epivascular, vascular and subvascular
and may have processes. In the case of pregnancy they may enlarge a lot of but
they are well connected. The innermost layer of myometrium is known as
the junctional zone, which becomes thickened in adenomyosis.
Perimetrium. The uterus is surrounded by "peritoneum."
Parametrium. The loose connective tissue
near the neck of uterus is called the "parametrium."
Uterus owerview. Haematoxylin and Eosin.
Upper – medium magnification, three layers are well seen. Lower – high
magnification, well prominent crypts in the endomethrium.
A panoramic view of the uterus showing the whole
thickness of the wall.
a =
endometrium (a proportionally thin layer, with a dark base as seen here.) This is a
mucosa, with epithelium and lamina propria and glands.
b =
wide, dark myometrium (smooth muscle in irregular, spiralling layers). This is
by far the widest layer in the wall.
c =
connective tissue perimetrium.
Major ligaments
Uterus lies in small pelvis and is held in place by several peritoneal ligaments, of which
the following are the most important (there are two of each): uterosacral
ligament and cardinal
ligaments
Other named ligaments near the uterus, i.e. the broad ligament, the
round ligament, the suspensory ligament of the ovary, the infundibulopelvic
ligament, have no role in the support of the uterus.
Hormonal adjusting of the
cyclic changes in the uterus
Menstrual
cycle, better ovarial-menstrual cycle
means periodic changes of female body, which occur in different organs and are
conneected with endocrine regulation.
Menstrual cycle includes periodic
changes of endomethrium (menstrual phase, postmenstrual or prolipherative and
premenstrual or secretory).
Ovarial cycle is connected with development of
follicle (follicular stage) its ovulation and lutein stgae (corpus luteum development).
Adequate changes could be seen in vagina, mammary
glands and e.t.c.
The length of menstrual cycle (usually 28 days) is
counted from the first day of bleeding to
the next one. The matter is, in
premenstrual phase progesteron of corpus lureum stimulies development and
secretion of uterine glands, when involution of corpus luteum begins,
progesterone volume in the blood sharply decreeses, thus promoting constriction
of endomethrial blood vessels (coiled arteries). Whithout normal blood supply endomethrium
undergo hypothrophy and distrophy and few hours later when blood passage is renewed the uppermost “dead” tissues are
removed. Usually the blood loss is about 100-200 ml.
Diagram of inter-relationships
between the anterior pituitary, ovary and uterus during the menstrual cycle.
Beginning at the upper left, the ovarian follicle enlarges under the influence
of high titers of FSH from the pituitary. As the follicle grows, its theca
interna produces increased amounts of estrogen which causes the endometrium
below to thicken. During this proliferative phase, the endometrial glands are
thin and straight and the coiled arteries increase in length.
At mid-cycle (about 14 days) there is a great surge of
LH from the pituitary, coinciding with the time of ovulation. The follicular
epithelium that remains behind undergoes a marked hyperplasia and
differentiates into granulosa lutein cells, which form the bulk of the new
corpus luteum. Under the influence of pituitary LH, these cells now produce
progesterone which, in turn, causes the endometrium to thicken somewhat further
and develop very wide, tortuous, sacculated glands, ready for implantation by
an ovum. Estrogen is still being produced by the theca interna.
The wall of the uterus changes during the menstrual
cycle, as shown diagramatically here.
Proliferative Phase
In the proliferative phase, facilitated by FSH,
the endometrium thickens, connective tissue is renewed, along with glandular
structures and ehlicrine arteries. Oestrogen causes the endometrial stroma to
become deep and richly vascularised.
Simple tubular glands in the stratum functionalis
open out onto the surface, and the endometrium thickens.
Secretory Phase
In the secretory phase, facilitated by LH, the
endometrial glands become cork-screw shaped, and filled with glycogen.
They secrete a glycogen rich secretion during the secretory phase (after
ovulation).
Menses
Decreased levels of LH and progesterone result in the menstrual
phase, or menses. During menses (shedding of the uterine
lining, which occurs if the egg is not fertilised) the spiral arterioles
in the stratum functionalis layer contract, resulting in ischaemia,
and degeneration of the functionalis layer. The arteries rupture, and the rapid
blood flow dislodges the necrotic functional layer, which is lost. (The basal
layer is unaffected, because it is supplied by straight arteries).
Pituitary hormones control most ovarian functions.
Follicle-stimulating hormone (FSH) stimulates follicular growth and synthesis
of estrogen by the granulosa cells. Luteinizing hormone (LH) induces ovulation
and transforms the granulosa layer and the theca interna into an actively
secreting gland, the corpus luteum. Estrogen and progesterone produced in the
ovary act on the hypothalamus, stimulating or inhibiting the liberation of
gonadotropin-releasing hormone (GnRH).
At about 28 days, if there is no implantation, the
titers of estrogen and progesterone fall off as the corpus luteum degenerates,
and, at the same time, the coiled arteries of the endometrium clamp down. Thus
deprived of nourishment, the endometrium begins to break up and slough off in
menstruation. Only the basal layer of the endometrium will remain. Hormonal
feedback now tells the pituitary to increase its secretion of FSH, thus
starting the cycle all over again. In the event of pregnancy, of course, the
corpus luteum is preserved, the production of estrogen and progesterone remains
high, and the glandular endometrium is maintained. In time, the developing
placenta itself produces an LH-like chorionic gonadotropin and, later, both
estrogen and progesterone, in order to maintain the appropriate hormonal
environment for the developing fetus and its needs.
Most prominent changes could be found in endomethrium.
Light microscopy of endometrium in different phases of menstrual cycle
(prolipherative early and late secretory) and in pregnancy.
Photomicrograph of the superficial
layer of the endometrium during the proliferative phase.
The surface epithelium and the uterine glands are embedded in a lamina propria
made of very loose connective tissue. PT stain. Medium
magnification.
Photomicrograph of straight uterine glands in the deep
endometrium during the proliferative phase. Smooth muscle of the myometrium is
also seen. H&E stain. Medium magnification.
Photomicrograph of uterine glands. During the luteal phase, the uterine glands become
tortuous and their lumen is filled with secretions. Some edema is present in
the connective tissue. H&E stain. Medium magnification.
Changes in the uterine glands and in the gland cells
during the menstrual cycle. In the proliferative stage the glands are straight
tubules, and their cells show no secretory activity. In the initial secretory
phase the glands begin to coil, and their cells accumulate glycogen in the
basal region. In the late secretory phase the glands are highly coiled, and
their cells present secretory activity at their apical portion.
cervix
Mucosa of the cervix with its lumen
to the left. (The uterus would lie above this region and the
vagina below.) Notice how the mucosal glands slant upwards. They produce a
mucoid secretion. Arrows = small blood vessels.
Sharp transition from simple columnar epithelium of
the endocervix to non-ceratinized stratified squamous epithelium of the
ectocervix and vagina.
vagina
The vagina, (from Latin,
literally "sheath" or
"scabbard" ) is a
fibromuscular tubular
tract leading from the uterus
to the exterior of the body in female placental
mammals and marsupials,
or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates
also have a vagina, which is the terminal part of the oviduct. The
Latinate plural (rarely used in English) is
vaginae. In common speech, the
term "vagina" is often used to refer to the vulva or female
genitals generally; strictly speaking, the vagina is a specific internal
structure and the vulva is the exterior genitalia only.
The human vagina is an
elastic muscular canal that extends from the cervix to the vulva.[1] Although
there is wide anatomical variation, the length of the unaroused vagina is
approximately 6 to
If the woman stands upright, the vaginal tube points in an
upward-backward direction and forms an angle
of slightly more than 45 degrees with the uterus. The vaginal opening is at the
caudal end of the
vulva, behind the opening of the urethra.
The upper one-fourth of the vagina is separated from the rectum by the rectouterine
pouch. Above the vagina is Mons Veneris.
The vagina, along with the inside of the vulva, is reddish pink in color, as
with most healthy internal mucous membranes in mammals.
Vaginal
lubrication is provided by the Bartholin's
glands near the vaginal opening and the cervix. The
membrane of the vaginal wall also produces moisture, although it does not
contain any glands. Before and during ovulation,
the cervix's
mucus glands secretes different variations of mucus, which
provides a favorable alkaline environment in the vaginal canal to maximize the
chance of surivival for sperm.
The hymen
is a thin membrane
of connective tissue
which is situated at the opening of the vagina. As with many female animals,
the hymen covers the opening of the vagina from birth until it is ruptured
during activity. The hymen may rupture during sexual or non-sexual activity.
Vaginal penetration may rupture the hymen. A pelvic
examination, injury, or certain types of
exercises, such as horseback
riding or gymnastics
may also rupture the hymen. Sexual intercourse does not always rupture the
hymen. Therefore, the presence or absence of a hymen does not indicate virginity or prior
sexual activity.
The
vagina has several biological functions.
1. Uterine secretions
2.
The vagina provides a path for menstrual blood and tissue
to leave the body. In industrial societies, tampons, menstrual cups
and sanitary napkins
may be used to absorb or capture these fluids.
3. Sexual activity
4.
The concentration of the nerve endings that lie close to the entrance of a
woman's vagina can provide pleasurable sensation during sexual activity, when
stimulated in a way that the particular woman enjoys. During sexual arousal
and particularly stimulation of the clitoris,
the walls of the vagina self-lubricate,
reducing friction during sexual
activity. Research has found that portions of the
clitoris extend into the vulva and vagina.
With arousal, the vagina lengthens rapidly to an average of about
An erogenous zone
referred to commonly as the G-spot
is located at the anterior wall of the vagina, about five centimeters in from
the entrance. Some women experience intense pleasure if the G-spot is
stimulated appropriately during sexual activity. A G-Spot orgasm may be
responsible for female
ejaculation, leading some doctors and
researchers to believe that G-spot pleasure comes from the Skene's glands,
a female homologue of the prostate,
rather than any particular spot on the vaginal wall.http://en.wikipedia.org/wiki/Vagina
- _note-10#_note-10 Some researchers deny the existence of
the G-spot.
![vagina(l)[1]](20%20Menstrual%20cycle.%20%20Mammary%20glands.files/image058.jpg)
Childbirth
During childbirth,
the vagina provides the channel to deliver the baby from the uterus to its
independent life outside the body of the mother. During birth, the vagina is
often referred to as the birth canal. The vagina is remarkably elastic and
stretches to many times its normal diameter during vaginal birth.
Vagina with stratified squamous epithelial lining
and a wide lamina propria (some people would call the deeper portion of this
layer the submucosa. The two connective tissue Iayers merge because there is no
muscularis mucosae to separate them.) Notice distended venules in the
connective tissue and the way the smooth muscle of the muscularis externa lies in loose
strands.
During the entire life of a woman, the structure and
functions of the vaginal epithelium and of the endometrium depend on ovarian
hormones.
Photomicrograph of stratified
squamous epithelium of the vagina supported by a dense connective tissue.
The cytoplasm of these epithelial cells is clear because of accumulated
glycogen. PSH stain. Medium
magnification.
Mammary glands
The mammary gland is a compound
branched tubular-alveolar gland with macroapocrine mode of secretion. It derives originally as multiple epithelial ingrowths
from the skin. The epithelium of its ducts and secretory units is directly
continuous with the epidermis of the nipple area. Inactive mammary gland is
composed mostly of pale, wide, connective tissue interlobular septa with
scattered lobules containing small dark cross-cuts of many intralobular ducts.
There are very few, if any, secretory alveoli in the inactive gland. Much of
the interlobular tissue is adipose tissue. Note that the intralobular ducts
branch frequently but have no secretory acini at their endings.
The
mammary glands are modified glands of the skin. Their development resembles
that of sweat glands. They are compound branched alveolar glands, which consist
of 15-25 lobes separated by dense interlobar connective tissue and fat. Each
lobe contains an individual gland. The excretory duct of each lobe, also called
lactiferous duct, has its own opening on the
nipple.
The
lactiferous duct has a two layered epithelium -
basal cells are cuboidal whereas the superficial cells are columnar. Beneath
the nipple, the dilated lactiferous duct forms a lactiferous
sinus , which functions as a reservoir for the milk. Branches of the
lactiferous duct are lined with a simple cuboidal epithelium. The secretory
units are alveoli, which are lined by a cuboidal or columnar epithelium. A layer of myoepithelial cells is always present between the
epithelium and the basement membrane of the branches of the lactiferous duct
and the alveoli.
The
above description corresponds basically to the appearance of the resting
mammary gland. Pregnancy induces a considerable growth of the epithelial
parenchyma leading to the formation of new terminal branches of ducts and of
alveoli in the first half of pregnancy. Growth is initiated by the elevated
levels of oestrogen and progesterone produced in the ovaries and placenta.
Concurrently, a reduction in the amount of intra- and interlobular connective
tissue takes place. The continued growth of the mammary glands during the
second half of pregnancy is due to increases in the height of epithelial cells
and an expansion of the lumen of the alveoli. They
contain a protein-rich (large amounts of immunoglobulins) eosinophilic
secretion - the colostrum or foremilk).
Secretion
of milk proteins proceeds by exocytosis (merocrine secretion), whereas lipids
are secreted by apocrine secretion. Secretion is stimulated by prolactin. Prolactin secretion in turn is stimulated by
sensory stimulation of the nipple, which also initiates the so-called milk ejection reflex via the secretion of oxytocin from the neurohypophysis. Milk is ejected from
the glandular tissue into the lactiferous sinuses - now it's up to the baby to
get things out.
Dense connective tissue and fat cells lie in the
surrounding interlobular septa. The connective tissue stroma within the lobule
is more cellular than the interlobular connective tissue outside.
Acinus is the structural unite of mammary gland, it consists
of lactocytes pyramidal secretory cells arranged in tubular-alveolar-shaped
secretory portion and intercallated lqactiferous duct.
Mammary gland is proliferating in pregnancy, lobules
now enlarging as secretory acini sprouts from the intralobular duct systems.
The septa (pale pink) are becoming compressed. Note large interlobular ducts
lying in the septa. Lobules now seem more comparable to the kind of thing seen
in the salivary gland. Secretion of watery cholostrum precedes the secretion of
true milk, which does not come until after the birth of the child.
Lactating mammary gland with alveoli (acini) very
distended with milk secretion, which stains bright pink here. Notice the
branching, tubular shapes to some of the secretory units. The lobule to the
right has emptied its contents. Notice how thin and compressed the interlobular
connective tissue septa are now (very thin, pink strands around groups of the
empty alveoli).
Schematic drawing of the female breast showing
inactive and active mammary glands. Each lactiferous duct with its accompanying
smaller ducts is a gland in itself and constitutes the lobes of the gland.
Photomicrograph of lactating mammary gland. Several
alveoli are filled with milk, visible as granular material. The vacuoles in the
lumen and in the alveolar cell cytoplasm represent the lipid portion of milk. PT
stain. Medium magnification.
Changes in the mammary gland. A: In nonpregnant
women, the gland is quiescent and undifferentiated, and its duct system is
inactive. B: During pregnancy, alveoli proliferate at the ends of the
ducts and prepare for the secretion of milk. C: During lactation,
alveoli are fully differentiated, and milk secretion is abundant. Once
lactation is completed, the gland reverts to the nonpregnant condition.
Secreting cells from the mammary gland. From left to
right, note the accumulation and extrusion of lipids and proteins. The proteins
are released through exocytosis.
Milk, which is produced by mammarey glands is compound
secretory product including water, salts, proteins,
lipids, carbohydrates, vitamins, antibodies and so on. Constituency og milk
varies very much in different periods of feeding
baby.
Endocrine regulation of
lactation is performed
mainly by prolactine, which is produced by adenopituitary, but normal
lactation requires enough growth-hormone, thyroxin and so on. Milk
effusion from lactocytes has dual regulation: irritation of nipple nerve
endings in suckling promotes throwing out the oxytocin of anterior hypothalamus
into the blood (through axo-vasal synapses of neuropituitary) thus stimulying
of myoepithelial cells, which surround the secretory portions of mammary gland
acini. Contractions of these stellate cells push out the milk from
lactocytes. The apical portions of secretory cells are destroing at this
moment. Some milk may be deposed in lactiferous sinuses, which lie right under th nipple.
The glandular tissue of the mammary gland is
frequently subject to pathological changes - the most serious being mammary
cancer, which is the most frequent malignancy in women (about 6.5% of all women
develop the disease).
Student’s Practical
Activities
Task
No 1. Students must know and
illustrate such a histologic specimens.
Specimen 1. Uterus in premenstrual period of cycle.
Haematoxylin and Eosin.
Endometrium in the early secretory stage. Glands are
becoming tortuous and sacculated under the influence of progesterone. Their
glycogen-rich mucoid secretion is stored within the glands, pending a possible
implantation of an embryo.
At a low magnification, the glands are seen to have
developed an irregular corkscrew configuration and the endometrium approaches
its maximum thickness.
Under the influence of progesterone, the glandular
epithelium is stimulated to synthesize glycogen. Initially glycogen accumulates
to form vacuoles in the basal aspect of the cells, thus displacing the nuclei
towards the centre of the now tall columnar cells. This basal vacuolation of
the cells is a characteristic feature of anearly secretory endometrium as seen
at a high magnification.
Illustrate and indicate:
1. Functional portion of the endometrium: a) compactum
stratum; b) spongiosum stratum; c) simple tubular branched glands.
2. Basal portion: a) fundus of the gland.
3. Veins.
4. Arteries.
5. Myometrium.
Specimen
2. Uterus at the postmenstrual period
of the cycle.
Haematoxylin
and Eosin.
Overview
of uterine wall in the early post-menstrual stage. Only the basal layer of
endometrium is present. Glands are sparse.
Illustrate and indicate:
1. Functional portion of the endometrium:
a) compactum stratum;
b) spongiosum stratum;
c) simple tubular branched glands.
2. Basal portion: a) fundus of the gland.
3. Veins.
4. Arteries.
5. Myometrium.
At a
low-magnification a specimen illustrates the myometrium and a relatively thin
endometrium consisting of the stratum basalis, stratum spongiosum and stratum
compactum. At a the postmenstrual period, the stroma
of the stratum functionalis (spongiosum plus compactum) has proliferated but
the simple tubular glands have hawever barely proliferated into the stratum
compactum. At high magnification the proliferating glandular epithelium is seen
to consist of low columnar cells. Occasional mitotic figures can be seen. The
highly cellular connective tissue stroma is noted to almost devoid of collagen
fibres, that resembles primitive mesenchyme.
Illustrate
and indicate: 1. Endomitrium: a) cuboidal epithelium; b)
uterus gland; 2. Connective tissue;3.
Blood vessels.
Specimen 3.
Mammary gland.
Haematoxylin and Eosin.
At a low magnification, the lobules of the mammary
glands are seen to form islands of a glandular tissue within an extensive mass
of a dense fibrous and adipose connective tissue. At higher magnification, the
lobules are seen to consist of alveolar ducts lined with a cuboidal epithelium
supported by a prominent basement membrane. Similar sweat glands, a
discontinuous layer of myoepithelial cells lies between the duct-lining cells
and the basement membrane. During the reproductive years, the duct epithelium
undergoes cyclic changes under the influence of ovarian hormones. Early in the
cycle, the duct lumina are not clearly evident but later in the cycle the
lumina become more prominent and may contain an eosinophilic secretion.
The interlobular connective tissue is usually dense
and fibrous whereas the connective tissue within the lobule is loose, highly
cellular, rarely contains fat, and has a rich capillary network.
Illustrate and indicate:
1. Lobule. Interlobular septum.
2. Alveolar secretory portion (lactocytes).
3. Alveolar lactiferous duct.
4. Myoepitheliocytes.
5. Interlobular milk duct.
References:
a)
basic
1.
Practical classes materials.
3.
Stevens A. Human Histology / A.
Stevens, J. Lowe. – [second
edition]. –Mosby, 2000. –
P. 327-350.
4.
Wheter’s Functional Histology : A
Text and Colour Atlas / [Young B.,
Lowe J., Stevens A., Heath J.]. – Elsevier
Limited, 2006. – P. 359-392.
5.
Ross M. Histology : A Text and Atlas
/ M. Ross W.Pawlina. – [sixth
edition]. – Lippincott Williams and Wilkins, 2011. – P. 845-894.
b)
additional
6. Eroschenko V.P. Atlas of Histology with functional
correlations / Eroschenko V.P. [tenth edition]. – Lippincott
Williams and Wilkins, 2008. – P. 455-488.
7. Charts:
http://intranet.tdmu.edu.ua/index.php?dir_name=kafedra&file_name=tl_34.php#n15
8. Volkov K. S. Ultrastructure of cells and tissues / K. S. Volkov, N. V.
Pasechko. – Ternopil : Ukrmedknyha, 1997. –
P.100-101.
http://en.wikipedia.org/wiki/Histology
http://www.meddean.luc.edu/LUMEN/MedEd/Histo/frames/histo_frames.html
http://www.udel.edu/biology/Wags/histopage/histopage.htm
Methodical instruction has been worked out by: ass. Lytvynyuk S.O.