MUSCULAR TISSUE
Muscle cells are structurally and functionally specialized for contraction, which requires 2 types of special protein filaments called myofilaments: thin filaments containing actin and thick filaments containing myosin.
Nearly all muscle cells arise from mesoderm. Exception: Smooth muscles of the iris arise from ectoderm. Muscle tissues are composed of groups of muscle cells organized by connective tissue elements. Their arrangement allows the groups to act together or separately, generating mechanical forces of varying strength. Muscle cells are typically longer than they are wide, sometimes reaching lengths of
Types of Muscle Tissue: The main muscle tissue types are smooth muscle and the 2 types of striated muscle, skeletal and cardiac. Smooth muscle is found mainly in the walls of hollow organs (eg, intestines and blood vessels); its contraction is slow, often in waves, and under involuntary control. In histologic section, it lacks the banding pattern, or striation, seen in the other type 2 types. Skeletal muscle is found mainly in association with bones, which act as pulleys and levers to multiply the force of its quick, strong, voluntary contractions. Cardiac muscle is found exclusively in the walls of the heart; its contractions are quick, strong, rhythmic, and involuntary.
SKELETAL MUSCLE
Skeletal muscle arises from mesenchyme of mesodermal origin. Mature skeletal muscle fibers are elongated, unbranched, cylindrical, multi-nucleated. The flattened, peripheral nuclei lie just under the sarcolemma (muscle cell plasma membrane); most of the organelles and sacroplasm (muscle cell cytoplasm) are near the poles of the nuclei. The sarcoplasm contains many mitochondria, glycogen granules, and an oxygen-binding protein called myoglubin, and it accumulates lipofuscin pigment with age. Mature skeletal muscle fibers cannot divide.
Myofilaments In skeletal muscle fibers, these are of 2 major types. a. Thin filaments and thick filaments. The grouping of myofilaments into parallel bundles of thick and thin filaments called myofibrils. Each muscle fiber may contain several myofibrils, the number depending on its size.
At both light and electron microscopic levels, each myofibril exhibits repeating, linearly arranged, functional sub-units called sarcomeres, which have bands (striations) running perpendicular to the long axis of the myofibril. The sarcomeres of each myofibril lie in register with those in adjacent myofibrils so that their bands appear continuous. The sarcomere is separated from its neighbors at each end by a dense Z line, or Z disk. A major protein of the Z disk, alpha actinin, anchors one end of the thin filaments and helps maintain proper spatial distribution. The thin filaments extend to the middle of the sarcomere. The center of each sarcomere is marked by the M line, which holds the thick filaments in place. The thick filament bundles lie at the center of each sarcomere, are bisected by the M line, and overlap the free ends of the thin filaments. The pattern of overlapping between the thick and thin filaments is responsible for the banding pattern and differs depending on the myofibrils’ state of contraction.
The bands With the light microscope, skeletal muscle exhibits alternating light- and dark-staining bands running perpendicular to the long axis of the muscle fibers.
I bands The light-staining bands contain only thin filaments. They are known as I bands (isotropic) because they do not rotate polarized light. Each I band is bisected by a Z line. Thus each sarcomere has 2 half I bands, one at each end.
A bands One dark-staining band lies in the middle of each sarcomere and shows the position of the thick filament bundles. This is known as an A band (anisotropic) because it is birefrmgent (rotates polarized light). At the EM level, each A band has a lighter-staining central region termed the H band, which is bisected by an M line. The H band lies between the free ends of the thin filaments and contains only the shafts of myosin molecules. The darker peripheral portions of the A bands are regions of overlap between the thick and thin filaments and contain the heads of the myosin molecules. The interaction between the myosin heads of the thick filaments and the free ends of the thin filaments causes muscle contraction.
The sarcolemma and muscle fibrils are partially cut, showing the following components: The invaginations of the T system occur at the level of transition between the A and I bands twice in every sarcomere. They associate with terminal cisternae of the sarcoplasmic reticulum (SR), forming triads. Abundant mitochondria lie between the myofibrils. The cut surface of the myofibrils shows the thin and thick filaments. Surrounding the sarcolemma are a basal lamina and reticular fibers.
Muscle contraction, initiated by the binding of Ca2+ to the TnC unit of troponin, which exposes the myosin binding site on actin (cross-hatched area). In a second step, the myosin head binds to actin and the ATP breaks down into ADP, yielding energy, which produces a movement of the myosin head. As a consequence of this change in myosin, the bound thin filaments slide over the thick filaments. This process, which repeats itself many times during a single contraction, leads to a complete overlapping of the actin and myosin and a resultant shortening of the whole muscle fiber. I, T, C are troponin subunits.
The drawing at the upper right shows branching of a small nerve with a motor end-plate for each muscle fiber. The structure of one of the bulbs of an end-plate is highly enlarged in the center drawing. Note that the axon terminal bud contains synaptic vesicles. The region of the muscle cell membrane covered by the terminal bud has clefts and ridges called junctional folds. The axon loses its myelin sheath and dilates, establishing close, irregular contact with the muscle fiber. Muscle contraction begins with the release of acetylcholine from the synaptic vesicles of the end-plate. This neurotransmitter causes a local increase in the permeability of the sarcolemma. The process is propagated to the rest of the sarcolemma, including its invaginations (all of which constitute the T system), and is transferred to the sarcoplasmic reticulum (SR). The increase of permeability in this organelle liberates calcium ions (drawing at upper left) that trigger the sliding filament mechanism of muscle contraction. Thin filaments slide between the thick filaments and reduce the distance between the Z lines, thereby reducing the size of all bands except the A band. H, H band; S, sarcomere.
Sarcoplasmic reticulum This is the smooth endoplasmic reticulum of striated muscle cells, specialized to sequester calcium ions. In skeletal muscle, it consists of an anas-tomosing complex of membrane-limited tubules and cisternae that ensheathe each myofibril. At each A-I band junction, a tubular invagination of the sarcolemma termed a transverse tubule, or T tubule, penetrates the muscle fiber and comes to lie close to the surface of the myofibrils. On each side of the T tubule lies an expansion of the sarcoplas-mic reticulum termed a terminal cisterna. A complex of 2 terminal cisternae and an intervening T tubule constitutes a triad. Triads have an important role in initiating muscle contraction.
Energy Production: Muscles use glucose (from stored glycogen and from the blood) and fatty acids (from the blood) to form the ATP and phosphocreatine that provide chemical energy for contraction. When ATP is not available, actin-myosin binding becomes stabilized, accounting for rigor mortis, the muscular rigidity that occurs shortly after death.
Other Components of the Sarcoplasm
Glycogen is found in abundance in the sarcoplasm in the form of coarse granules. It serves as a depot of energy that is mobilized during muscle contraction.
Another component of the sarcoplasm is myoglobin; this oxygen-binding protein, which is similar to hemoglobin, is principally responsible for the dark red color of some muscles. Myoglobin acts as an oxygen-storing pigment, which is necessary for the high oxidative phosphorylation level in this type of fiber. For obvious reasons, it is present in great amounts in the muscle of deep-diving ocean mammals (eg, seals, whales). Muscles that must maintain activity for prolonged periods usually are red and have a high myoglobin content. Mature muscle cells have negligible amounts of rough endoplasmic reticulum and ribosomes, an observation that is consistent with the low level of protein synthesis in this tissue.
Organization of the Skeletal Muscles:
Named muscles are bundles of muscle fascicles surrounded by a sheath of dense connective tissue termed the epimysium. Each fascicle is a bundle of muscle fibers surrounded by a dense connective tissue sheath called the perimysium, which consists of septumlike inward extensions of epimysium. Each muscle fiber is a bundle of myofibrils surrounded by a delicate connective tissue sheath termed the endo-mysium, which consists of a basal lamina and a loose meshwork of reticular fibers. Each myofibril is a bundle of myofilaments surrounded by an investment of sarcoplasmic reticulum, with a triad at both A-I junctions of each sarcomere. The connective tissue investments are continuous with one another. They bind together subunits that function together and separate subunits that function independently.
CARDIAC MUSCLE
Cardiac muscle arises as parallel chains of elongated splanchnic mesenchymal cells in the walls of the embryonic heart tube (myoepicardial plate of visceral mesoderm – splanchnic layer).
Cardiac muscle cells are elongated, cilindrycal cells with one or 2 elongated, central nuclei. The sarcoplasm near the nuclear poles contains many mitochondria and glycogen granules and some lipofuscin pigment. Mitochondria lie in chains between the myofilaments. The arrangement of myofilaments yields a pattern of striations identical to that of skeletal muscle.
Sarcoplasmic reticulum and T tubule system The sarcoplasmic reticulum in cardiac muscle fibers is less organized than that of skeletal muscle and does not subdivide myofilaments into discrete myofibrillar bundles. Cardiac T tubules are located at the Z line instead of the A-I junction. In most cells, cardiac T tubules are associated with a single expanded cisterna of the sarcoplasmic reticulum; thus, cardiac muscle contains dyads instead of triads.
Intercalated disks These unique histologic features of cardiac muscle appear as dark transverse lines between the muscle fibers and represent specialized junctional complexes. With the electron microscope, intercalated disks can be seen to have 3 major components arranged in a stepwise fashion.
a. The fascia adherens, similar to a zonula adherens, is a half Z line found in the vertical (transverse) portion of the step. Its alpha actinin anchors the thin filaments of the terminal sarcomeres.
b. The macula adherens (desmosome) is the second component of transverse portion of the junction. It prevents detachment of the cardiac muscle fibers from one another during contraction.
c. The gap junction of intercalated disks comprise the horizontal (lateral) portion of the step. They provide electrotonic coupling between adjacent cardiac muscle fibers and pass the stimulus for contraction from cell to cell.
Organization of Cardiac Muscle: Because of the abundant capillaries in the endomysium of each fiber, cardiac muscle fibers appear more loosely arranged in histologic section than those of skeletal muscle. The whorled arrangement of cardiac muscle fibers in the wall of the heart accounts for the ability of the myocardium to “wring out” blood in the heart chambers.
Initiation of Cardiac Muscle Contraction: Unlike skeletal muscle fibers, which rarely contract without direct motor innervation, cardiac muscle fibers contract spontaneously with an intrinsic rhythm. The heart receives autonomic innervation that cannot initiate contraction but can speed up or slow down the intrinsic beat. The initiating stimulus for contraction is normally provided by a collection of specialized cardiac muscle cells called the sinoatrial node; it is delivered by other specialized fibers, called Purkinje fibers, to the other cardiac muscle cells (conductive system of the heart). The stimulus is passed between adjacent cells through the gap junctions of the intercalated disks. The gap junctions establish an ionic continuity among cardiac muscle fibers that allows them to work together as a functional syncytium.
SMOOTH MUSCLE
Most smooth muscle cells differentiate from mesenchymal cells of mesodermal origin in the walls of developing hollow organs of cardiovascular, digestive, urinary, and reproductive systems. During differentiation, the cells elongate and accumulate myofilaments. Smooth muscles of the iris arise from ectoderm.
Smooth Muscle Cells: Mature smooth muscle fibers are elongated, spindle-shaped cells with a single central ovoid nucleus. The sarcoplasm at the nuclear poles contains abundant mitochondria, some rough endoplasmic reticulum, and a large Golgi complex. Each fiber produces its own basal lamina, consisting of proteoglycan-rich material and type III collagen fibers.
Thin myofilaments The actin filaments of smooth muscle are like those of skeletal and cardiac muscle. They are always present in the cytoplasm and are anchored in dense bodies associated with the plasma membrane.
Thick filaments The myosin filaments of smooth muscle are less stable than those in striated muscle cells; they are not always present in the cytoplasm but seem to form in response to a contractile stimulus. Unlike the thick filaments in striated muscle cells, those in smooth muscle have heads along most of their length and bare areas at the ends of the filaments.
Organization of the myofilaments The filaments run mostly parallel to the long axis of smooth muscle fibers, but they overlap much more than those of striated muscle, accounting for the absence of cross striations. The greater overlap of thick and thin filaments results from the unique organization of the thick filaments and permits greater contraction. The ratio of thin to thick filaments in smooth muscle is about 12:1, and the arrangement of the filaments is less regular and crystalline than in striated muscle.
Sarcoplasmic reticulum Smooth muscle cells contain a poorly organized sarcoplasmic reticulum; these fibers have no T tubules and no dyads or triads.
Organization of Smooth Muscle: Unlike striated-muscle fibers, which abut end-to-end, smooth muscle fibers overlap to varying degrees and attach to one another by fusing their endo-mysial sheaths. The sheaths are interrupted by many gap junctions, which transmit the ionic currents that initiate contraction. Smooth muscle fibers form fascicles that vary in size but are usually smaller than those m striated muscle. The fascicles, each surrounded by a meager penmysium, are often organized in layers separated by the thicker epimysial connective tissue. Fibers in adjacent layers often lie perpendicular to one another.
REGENERATION OF MUSCLE TISSUE
The three types of adult muscle have different potentials for physiologic regeneration and reparative after injury.
Cardiac muscle physiologic regeneration occurs intracellular (cardiomyocytes are renewing their structural compounds mainly in diastole), but this muscular tissue has virtually no reparative capacity beyond early childhood. Defects or damage (e.g., infarcts) in heart muscle are generally replaced by the proliferation of connective tissue, forming myocardial scars.
In skeletal muscle, although the nuclei are incapable of undergoing mitosis, the tissue can undergo limited regeneration. The source of regenerating cells is believed to be the satellite cells. The latter are a sparse population of mononucleated spindle-shaped cells that lie within the basal lamina surrounding each mature muscle fiber. Because of their intimate apposition with the surface of the muscle fiber, they can be identified only with the electron microscope. They are considered to be inactive myoblasts that persist after muscle differentiation. After injury or certain other stimuli, the normally quiescent satellite cells become activated, proliferating and fusing to form new skeletal muscle fibers. A similar activity of satellite cells has been implicated in muscle hypertrophy, where they fuse with their parent fibers to increase muscle mass after extensive exercise. The regenerative capacity of skeletal muscle is limited, however, after major muscle trauma or degeneration.
Smooth muscle is capable of an active regenerative response. After injury, viable mononucleated smooth muscle cells and myofibroblasts of connective tissue undergo mitosis and provide for the replacement of the damaged tissue.
Cartilage cells can give rise to benign (chondroma) or malignant (chondrosarcoma) tumors.
In contrast to other tissues, hyaline cartilage is more susceptible to degenerative aging processes. Calcification of the matrix, preceded by an increase in the size and volume of the chondrocytes and followed by their death, is a common process in some cartilage. “Asbestiform” degeneration, frequent in aged cartilage, is due to the formation of localized aggregates of thick, abnormal collagen fibrils
MEDICAL APPLICATION
The fluorescent antibiotic tetracycline interacts with great affinity with recently deposited mineralized bone matrix. Based on this interaction, a method was developed to measure the rate of bone apposition—an important parameter in the study of bone growth and the diagnosis of bone growth diseases. Tetracycline is administered twice to patients, with an interval of 5 days between injections. A bone biopsy is then performed, and the sections are studied by means of fluorescence microscopy. The distance between the two fluorescent layers is proportional to the rate of bone apposition. This procedure is of diagnostic importance in such diseases as osteomalacia, in which mineralization is impaired, and osteitis fibrosa cystica, in which increased osteoclast activity results in removal of bone matrix and fibrous degeneration.
In the genetic disease osteopetrosis, which is characterized by dense, heavy bones (“marble bones”), the osteoclasts lack ruffled borders, and bone resorption is defective.
The organic matter embedded in the calcified matrix is type I collagen and ground substance, which contains proteoglycan aggregates and several specific multiadhesive glycoproteins, including osteonectin. Calcium-binding glycoproteins, notably osteocalcin, and the phosphatases released in matrix vesicles by osteoblasts promote calcification of the matrix. Other tissues containing type I collagen do not contain these glycoproteins or matrix vesicles and are not normally calcified. Because of its high collagen content, decalcified bone matrix is usually acidophilic.
The association of minerals with collagen fibers is responsible for the hardness and resistance of bone tissue. After a bone is decalcified, its shape is preserved, but it becomes as flexible as a tendon. Removal of the organic part of the matrix—which is mainly collagenous—also leaves the bone with its original shape; however, it becomes fragile, breaking and crumbling easily when handled.
When a bone is fractured, blood vessels are disrupted and bone cells adjoining the fracture die. The damaged blood vessels produce a localized hemorrhage and form a blood clot.
Soon the blood clot is removed by macrophages and the adjacent matrix of bone is resorbed by osteoclasts. The periosteum and the endosteum at the site of the fracture respond with intense proliferation producing a soft callus of fibrocartilage-like tissue that surrounds the fracture and covers the extremities of the fractured bone (Figure 8–18).
Primary bone is then formed by a combination of endochondral and intramembranous ossification. Further repair produces irregularly formed trabeculae of primary bone that temporarily unite the extremities of the fractured bone, forming a hard bone callus (Figure 8–18).
Stresses imposed on the bone during repair and during the patient’s gradual return to activity serve to remodel the bone callus. The primary bone of the callus is gradually resorbed and replaced by secondary bone, remodeling and restoring the original bone structure. Unlike other connective tissues, bone tissue heals without forming a scar.
Because the concentration of calcium in tissues and blood must be kept constant, nutritional deficiency of calcium results in decalcification of bones. Severely decalcified bones are more likely to fracture.
Decalcification of bone may also be caused by excessive production of PTH (hyperparathyroidism), which can cause increased osteoclastic activity, intense resorption of bone, elevation of blood Ca2+ and PO3– 4 levels, and abnormal deposits of calcium in the kidneys and arterial walls.
The opposite occurs in osteopetrosis (L. petra, stone), a disease caused by defective osteoclast function that results in overgrowth, thickening, and hardening of bones. This process can obliterate the bone marrow cavities, depressing blood cell formation and causing anemia and the loss of white blood cells.
Nutritional Deficiencies and Bone Remodeling
Especially during growth, bone is sensitive to nutritional factors. Calcium deficiency, which leads to incomplete calcification of the organic bone matrix, can be due either to a lack of calcium in the diet or a failure to produce the steroid prohormone vitamin D, which is important for the absorption of Ca2+ and> PO3–4 by the small intestine.
Calcium deficiency in children causes rickets, a disease in which the bone matrix does not calcify normally and the epiphyseal plate becomes distorted by the normal strains of body weight and muscular activity. Ossification processes at this level are consequently hindered, and the bones not only grow more slowly but also become deformed.
Calcium deficiency in adults gives rise to osteomalacia (osteon + Gr. malakia, softness), which is characterized by deficient calcification of recently formed bone and partial decalcification of already calcified matrix. Osteomalacia should not be confused with osteoporosis. In osteomalacia, there is a decrease in the amount of calcium per unit of bone matrix. Osteoporosis, frequently found in immobilized patients and in postmenopausal women, is an imbalance in skeletal turnover so that bone resorption exceeds bone formation.
Hormones Acting on Bone Tissue
In addition to PTH and calcitonin, several other hormones act on bone. The anterior lobe of the pituitary synthesizes growth hormone (GH or somatotropin), which stimulates the liver to produce insulin-like growth factor-1 (IGF-1 or somatomedin). IGF has an overall growth effect, especially on the epiphyseal cartilage. Consequently, lack of growth hormone during the growing years causes pituitary dwarfism; an excess of growth hormone causes excessive growth of the long bones, resulting in gigantism. Adult bones cannot increase in length even with excess IGF because they lack epiphyseal cartilage, but they do increase in width by periosteal growth. In adults, an increase in GH causes acromegaly, a disease in which the bones—mainly the long ones—become very thick.
The sex hormones, both male (androgens) and female (estrogens), have a complex effect on bones and are, in a general way, stimulators of bone formation. They influence the time of appearance and development of ossification centers and accelerate the closure of epiphyses.
Cancer originating directly from bone cells is fairly uncommon (0.5% of all cancer deaths) but a form called osteosarcoma can arise in osteoblasts. The skeleton is often the site of metastases from tumors originating from malignancies in other organs, most commonly from breast, lung, prostate, kidney, and thyroid tumors.
The variation in diameter of skeletal muscle fibers depends on factors such as the specific muscle and the age and sex, state of nutrition, and physical training of the individual. It is a common observation that exercise enlarges the musculature and decreases fat depots. The increase in muscle thus obtained is caused by formation of new myofibrils and a pronounced growth in the diameter of individual muscle fibers. This process, characterized by increased of cell volume, is called hypertrophy (Gr. hyper, above, + trophe, nourishment). Tissue growth by an increase in the number of cells is termed hyperplasia (hyper + Gr. plasis, molding), which takes place most readily in smooth muscle, whose cells have not lost the capacity to divide by mitosis.
Myasthenia gravis is an autoimmune disorder characterized by progressive muscular weakness caused by a reduction in the number of functionally active acetylcholine receptors in the sarcolemma of the myoneural junction. This reduction is caused by circulating antibodies that bind to the acetylcholine receptors in the junctional folds and inhibit normal nerve-muscle communication. As the body attempts to correct the condition, membrane segments with affected receptors are internalized, digested by lysosomes, and replaced by newly formed receptors. These receptors, however, are again made unresponsive to acetylcholine by similar antibodies, and the disease follows its progressive course.
30 Fun Facts about sceletal tissues!
1. It takes 17 muscles to smile and 43 to frown. Unless you’re trying to give your face a bit of a workout, smiling is a much easier option for most of us. Anyone who’s ever scowled, squinted or frowned for a long period of time knows how it tires out the face which doesn’t do a thing to improve your mood.
2. Babies are born with 300 bones, but by adulthood the number is reduced to 206. The reason for this is that many of the bones of children are composed of smaller component bones that are not yet fused like those in the skull. This makes it easier for the baby to pass through the birth canal. The bones harden and fuse as the children grow.
3. We are about
4. The strongest muscle in the human body is the tongue. While you may not be able to bench press much with your tongue, it is in fact the strongest muscle in your body in proportion to its size. If you think about it, every time you eat, swallow or talk you use your tongue, ensuring it gets quite a workout throughout the day.
5. The hardest bone in the human body is the jawbone. The next time someone suggests you take it on the chin, you might be well advised to take their advice as the jawbone is one of the most durable and hard to break bones in the body.
6. You use 200 muscles to take one step. Depending on how you divide up muscle groups, just to take a single step you use somewhere in the neighborhood of 200 muscles. That’s a lot of work for the muscles considering most of us take about 10,000 steps a day.
7. The tooth is the only part of the human body that can’t repair itself. If you’ve ever chipped a tooth you know just how sadly true this one is. The outer layer of the tooth is enamel which is not a living tissue. Since it’s not alive, it can’t repair itself, leaving your dentist to do the work instead.
8. It takes twice as long to lose new muscle if you stop working out than it did to gain it. Lazy people out there shouldn’t use this as motivation to not work out, however. It’s relatively easy to build new muscle tissue and get your muscles in shape, so if anything, this fact should be motivation to get off the couch and get moving.
9. Bone is stronger than some steel. This doesn’t mean your bones can’t break of course, as they are much less dense than steel. Bone has been found to have a tensile strength of 20,000 psi while steel is much higher at 70,000 psi. Steel is much heavier than bone, however, and pound for pound bone is the stronger material.
10. The feet account for one quarter of all the human body’s bones. You may not give your feet much thought but they are home to more bones than any other part of your body. How many? Of the two hundred or so bones in the body, the feet contain a whopping 52 of them.
11. Muscles can account for about 40% your body weight.
12. Muscles can only pull, they cannot, as some people assume, push.
13. The longest muscle has muscle cells that can be over a foot long.
14. The smallest muscles are in the middle of the ear;examples are the tensor tympani, and stapedius.
15. The strongest, pound for pound, are the masseters, the chewing muscles.
16. There are 640 individual names for muscles.
17. Muscles need OXYGEN and FOOD to function properly.
18. The hardest working muscles in the body are the muscles in the eye. It takes 17 muscles in the body to smile.
19. There are muscles in the root of our hair that gives us goose bumps!
20. You have all the muscle fiber you will ever have at birth. Once damaged they can’t be replaced.
21. Arnold Schwarzenegger has as many muscle fibers as you – They’re just thicker!
22. A single muscle cell of the sartorius muscle in the thigh can be more than
23. There are more than 600 voluntary muscles in the body.
24. The strongest muscle of the body is the masseter muscle used for chewing!
25. Your hand contains 20 different muscles.
26. If all your muscles could pull in one direction you could create a force of 25 tons!
27. Muscles account for approximately 40% of your body weight.
28. It takes 17 muscles in your face to smile, but it takes 43 muscles to frown.
29. You take approximately 5 million steps per year using your leg muscles!
30. Muscles and Bones provide the framework for our bodies and allow us to jump, run or just lie on the couch.
References:
a) main
1. Practical classes materials:
3. Stevens A. Human Histology / A. Stevens, J. Lowe. – [second edition]. –Mosby, 2000. – P. 65-76, 60-61, 227-250.
4. Wheter’s Functional Histology : A Text and Colour Atlas / [Young B., Lowe J., Stevens A., Heath J.]. – Elsevier Limited, 2006. – P. 101 – 122, 186 – 207.
5. Inderbir Singh Textbook of Human Histology with colour atlas / Inderbir Singh. – [fourth edition]. – Jaypee Brothers Medical Publishers (P) LTD, 2002. – P. 89-134.
6. Ross M. Histology : A Text and Atlas / M. Ross W.Pawlina. – [sixth edition]. – Lippincott Williams and Wilkins, 2011. – P. 198 – 218, 218 – 254, 310 – 352.
b) additional
1. Eroschenko V.P. Atlas of Histology with functional correlations / Eroschenko V.P. [tenth edition]. – Lippincott Williams and Wilkins, 2008. – P. 267-277, 281.
2. Junqueira L. Basic Histology / L. Junqueira, J. Carneiro, R. Kelley. – [seventh edition]. –
3. Charts:
http://intranet.tdmu.edu.ua/index.php?dir_name=kafedra&file_name=tl_34.php#inf3
4. Disk:
http://intranet.tdmu.edu.ua/data/teacher/video/hist/
5. Volkov K. S. Ultrastructure of cells and tissues / K.
http://intranet.tdmu.edu.ua/data/books/Volkov(atlas).pdf
http://en.wikipedia.org/wiki/Histology
http://www.meddean.luc.edu/LUMEN/MedEd/Histo/frames/histo_frames.html
