Histology of Muscles of the human body - Copy [A].pptx

this is about the microscopic nature of muscle tissue

1. Histology of Muscle Muscle Tissue 1

2. … Skeletal muscle cardiac muscle (L) smooth muscle 2

3. Myology (sarcology) Is science concerned with muscle and their accessory parts like tendons, aponeurosis & fascia. Muscles are organs that are capable of contraction, which is important for locomotion, movement and posture. Muscle tissue is characterized by its well-developed properties of contraction. Muscle develops from embryonic mesoderm. 3

4. TIP Specific nomenclature associated with muscle commonly involves the prefix sarco - or myo - . The cytoplasm of muscle fibers or cells is called sarcoplasm . The endoplasmic reticulum of fibers or cells is called sarcoplasmic reticulum. The plasmalemma of fibers or cells is called the sarcolemma . Individual muscle cells are called myocytes . 4

5. Muscle tissue Three types of muscle tissue can be distinguished on the basis of morphologic and functional characteristics and the structure of each type is adapted to its physiologic role. 1. Striated, voluntary or skeletal muscle 2. Specialized type of striated involuntary muscle called cardiac muscle 3. Non striated, involuntary or smooth muscle 5

6. I. Skeletal muscle Is composed of bundles of very long, cylindrical, multinucleated cells that show cross-striations. Their contraction is quick, forceful, and usually under voluntary control. It is caused by the interaction of thin actin filaments and thick myosin filaments whose molecular configuration allows them to slide upon one another. The forces necessary for sliding are generated by weak interactions in the bridges between actin and myosin. 6

7. Cardiac and smooth muscles II. Cardiac muscle : has cross-striations and is composed of elongated, branched individual cells that lie parallel to each other. At sites of end-to-end contact are the intercalated disks, structures found only in cardiac muscle. Contraction of cardiac muscle is involuntary, vigorous, and rhythmic. III. Smooth muscle: consists of collections of fusiform cells that do not show striations. Their contraction process is slow and not subject to voluntary control. 7

8. Skeletal Muscle Skeletal muscle, also known as striated or voluntary muscle, comprises some 40-50% of the body mass in adults and constitutes part of the largest organ system of the body. Skeletal muscle consists of muscle fibers, which are long, cylindrical multinucleated cells with diameters of 10–100 micro meter. Multinucleation results from the fusion of embryonic mesenchymal cells called myoblasts . The long oval nuclei are usually found at the periphery of the cell under the cell membrane. This characteristic nuclear location is helpful in discriminating skeletal muscle from cardiac and smooth muscle, both of which have centrally located nuclei. 8

9. Development of skeletal muscle 9

10. Connective tissue arrangements of skeletal muscles In skeletal muscles the myofibers are bound together in a similar manner to wires in a telecommunications cable. The connective tissue in the muscle serves to bind and integrate the action of the various contractile units. A thin and delicate connective tissue layer, known as the endomysium , surrounds each individual myofiber . 10

11. CT investment… Myofibers are grouped together in bundles or fascicles, which are also surrounded by connective tissue, known as the perimysium . The fascicles are surrounded and bound together by a further connective tissue coating known as the epimysium . All these connective tissue coatings ( endomysium , perimysium and epimysium ) contain collagen fibers, elastic fibers, fibroblasts and are richly vascularized. The three layers of CT extend from deep fascia to further protect and strengthen skeletal muscle 11

12. Connective tissue investment of skeletal muscle 12

13. Muscle types 13

14. Components of skeletal muscle cell. The cell membrane is called sarcolemma . The sarcolemma sends tubular invaginations within the muscle cell. These are called centrotubules . These centrotubules form the transverse or T-system within the cells. The nuclei are called sarcolemmal nuclei as they lie in contact with the sarcolemma . There are many nuclei in each cell. The major component of the cell is a collection of longitudinal fiber called myofibrils. These myofibrils lie in parallel longitudinal bundles and extend from one end of the fibre to the other. 14

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16. … A longitudinal section of striated muscle shows the parallel running fibres or muscle cells, surrounded by connective tissue. a. Each fibre shows alternative dark and light areas called bands which run at the right angles to the long axis of the fibre . b. The dark band is slightly basophilic or purplish with H&E stain. In polarizing microscopy, the dark bands are birefringent (i.e., they alter the polarized light in two planes).Therefore, the dark bands, being doubly refractive, are anisotropic and are given the name A band The A band is bisected by lighter H band or Henson’s line. The H band is further bisected by a light line called M line. 16

17. … c. The light band stains highly with basic dyes and rotates the plane of polarisation of light weakly, this is called isotropic or I band . It is also bisected by a Z band. The distance b/n two Z bands comprise a unit called Sarcomere . When seen by E.M. the muscle fibre is filled with two types of myofibrils called actin and myosin. The arrangement of the actin and myosin filaments within the muscle fibre is responsible for the striated appearance. 17

18. Myofibril 18

19. Internal structure of skeletal muscle fibre 19

20. Internal structure of skeletal muscle fibre 20

21. … During muscle contraction myosin fibrils slide between the actin fibrils and make contacts with each other and the two bands come close to each other. The T-system forms an anastomosing reticulum around the myofibrils. The arrangement is such that there is a tubular ring encircling each myofibril at the A-I junction . The rest of the myofibril is encircled by a reticulum of interconnecting tubes . 21

22. … The wave of depolarisation spreads form the motor end plate to each myofibril along the T-system as it is a continuation of the sarcolemma . At the A-I junction the endoplasmic reticulum is called terminal cisternae. The arrangement is – a transverse tubule or centrotubule is sandwiched on each side by a terminal cisternum of endoplasmic reticulum. This structure is called a muscle triad. When the wave of depolarisation spreads in the T-system it stimulates the terminal cisternae which in turn release the Ca++. 22

23. Structure & organization levels of skeletal muscle 23

24. Structure & organization levels of skeletal muscle 24

25. Structure & organization levels of skeletal muscle 25

26. Structure & organization levels of skeletal muscle 26

27. 2. Cardiac muscle It is a specialised type of striated muscle, which is found in myocardium of the heart and in the walls of pulmonary artery and aorta (nearer to the heart). It differs from the skeletal muscle in the following ways: Its striations are very faint and difficult to demonstrate by routine H&E staining. At regular intervals the cytoplasm shows a dark transverse line called intercalated disc. These discs are sites of cell junction. 27

28. Cardiac muscle (myocardium) 28

29. Cardiac muscle The adjoining cell membranes are attached by desmosomes and gap junctions, which enable all the cells to act as a single muscle. The cardiac muscle shows intercalated discs in two directions (a) Transverse intercalated discs revealing end to end contact (b) Lateral intercalated discs show contacts made between portion of two adjoining lateral sides. III . The cells appear to branch when seen by E.M. It is seen that the site of branching are actually cells attached along a portion of their length. 29

30. Cardiac muscle cells 30

31. … IV . The nucleus is central in position. V. Each fibre has a single nucleus. VI. There is perinuclear light zone, where there are no myofibrils. These area appears as a space around the nucleus. VIII. By E.M. a. Myofibrils are not very distinctive. b. The mitochondria and endoplasmic reticulum are surrounded on all sides by myofilaments . c. T-system surround the myofibrils at the Z line. 31

32. Internal structure of cardiac muscle fibre 32

33. Internal structure of cardiac muscle fibre 33

34. … d. Myoglobulin and glycogen are abundant in cardiac muscle. e. Sarcoplasmic reticulum is less than that in the skeletal muscle. IX. The cardiac muscle shows a spontaneous rhythm of contraction and relaxation called myogenic rhythm. 34

35. 3. Smooth muscle These cells appear to be non striated under L.M. I. Each isolated cell is spindle shaped . II. The cytoplasm takes a dark eosinophilic stain due to the myoglobulin . It shows very fine longitudinal striations due to myofilaments . III. The nucleus is central. Each cell is mononucleated . It is elongated in a stretched muscle and wavy in contracted cell. IV. They lie in parallel fasciculi . The blood vessels and nerves lie in the septa which separates the fasciculi . 35

36. Location of smooth muscles in the body 36

37. Arrangement of smooth muscle fibre 37

38. Smooth muscle V. The arrangement of fasciculi varies: a. They are parallel to the line of contraction, when action in one direction is required e.g. muscularis externa of the gut wall. These can be arranged longitudinally, circularly or obliquely. b. When the action is reduction in surface area in a particular plane, the fasciculi lying in that plane interweave with each other as in the muscularis mucosa of the intestines. VI. Like the skeletal muscle fibres the sarcolemma is surrounded by a basement membrane and reticular fibres except at some sites where the cells make contact with each other. 38

39. Smooth muscle cells 39

40. … VII. By E.M. The spindle shaped cells interdigitate with each other. They contain actin and myosin filaments within the sarcoplasm . They are anchored to dense bodies. When they contract the entire myosin filament makes contact with the entire actin filament. VIII. The cells are attached to each other by gap junctions. This enables the smooth muscles to contract as large single cell. 40

41. Arrangement of myofibrils of smooth muscle cell 41

42. … IX. Smooth muscles are of two types 1. Unitary muscles a. Few nerves b. Contraction is myogenic c. Found in walls of hollow viscera. d. Nervous control is to enhance or depress the rate and force of the rhythmic contraction. 2. Multi-unit muscles a. Have abundant nerve supply b. Contraction is initiated by nervous action c. Small groups of muscles operate independently e.g. muscles of iris and walls of large arteries. 42

43. Comparison of skeletal, cardiac and smooth muscle tissues 43

44. Comparison of skeletal, cardiac and smooth muscle tissues 44

45. Comparison of skeletal, cardiac and smooth muscle tissues 45

46. Comparison of skeletal, cardiac and smooth muscle tissues 46

47. Comparison of skeletal, cardiac and smooth muscle tissues 47

48. Comparison of Skeletal, Cardiac & Smooth Muscle Cells Skeletal Muscle Cell: Cardiac Muscle: Smooth Muscle Cell: Elongated Cells Branching Cells Spindle-Shaped Cell Multiple Peripheral Nuclei Single Central Nucleus Single Central Nucleus Visible Striations Visible Striations Lack Visible Striations Voluntary Involuntary Involuntary Shape of the muscle fiber Number of nuclei per cell Microscopic Appearance Nerve control 48