Muscular tissue

General Histology - Muscular tissue
Dr.Nimoshini

1. MUSCULAR TISSUE DR.G.NIMOSHINI Post graduate student Department of Oral Pathology & Microbiology SRM Dental College, Ramapuram , Chennai, India

2. INTRODUCTION Latin – musculus (mouse). Mice moving under the skin. Greek- sarco (flesh). Over 700 skeletal muscles. Distributed almost everwhere in the body.

3. Muscle Derived from mesoderm , by modification of cells into muscle fibres.

4. Muscle tissue

5. SPECIAL TERM Used for the various cytoplasmic organelles of the muscle fibers Plasma membrane- sarcolemma Cytoplasm- sarcoplasm Smooth endoplasmic reticulum- sarcoplasmic reticulum Mitochondira-sarcosomes

6. Muscular System Functions Body movement Maintenance of posture Respiration Production of body heat Communication Constriction of organs and vessels Heart beat

7. Properties of Muscle Excitability Capacity of muscle to respond to a stimulus Contractility Ability of a muscle to shorten with force Extensibility Muscle can be stretched to its normal resting length and beyond to a limited degree Elasticity Ability of muscle to recoil to original resting length after stretched

8. Classification of muscles Contractile cell functioning as Multicellular contractile units

9. Muscle Tissue Types Skeletal Attached to bones Nuclei multiple and peripherally located Striated, Voluntary and involuntary (reflexes) Smooth Walls of hollow organs, blood vessels, eye, glands, skin Single nucleus centrally located Not striated, involuntary, gap junctions in visceral smooth Cardiac Heart Single nucleus centrally located Striations, involuntary, intercalated disks

10. Contractile cell functioning as single-cell contractile units: Myoepithelial cells(found in association with secretory acini ) Myofibroblasts (involved in wound healing) Myoid cells(found around seminiferous tubules) Pericytes (smooth muscle like cells that surround blood vessels)

11. Skeletal Muscle Structure Muscle fibers or cells Develop from myoblasts Numbers remain constant Connective tissue Nerve and blood vessels

12. STRUCTURE OF MUSCLE FIBER CT EPIMYSIUM :- Encloses whole muscle CT PERIMYSIUM :- Encloses each fasciculus(bundle) CT ENDOMYSIUM :-Encloses each muscle fibres.

13. STRUCTURE OF MUSCLE FIBERS Cylindrical in shape Outside lies connective tissue endomysium with some fibroblasts, collagen fibrils ,capillaries. A. Skeletal muscle mass; B. Cross­ section of muscle; C. One muscle fasciculus

14. MUSCLE FIBRE Cell membrane of fibre is sarcolemma Cytoplasm of muscle is known as Sarcoplasm

15. Connective Tissue, Nerve, Blood Vessels Connective tissue External lamina Endomysium Perimysium Fasciculus Epimysium Fascia Nerve and blood vessels Abundant

16. Parts of a Muscle

17. STRUCTURE EMBEDDED WITHIN SARCOPLASM :- Nuclei Myofibril Golgi apparatus Mitochondria Sarcoplasm reticulum Ribosomes Glycogen Lipids

18. MYOFIBRIL & ITS MICROSCOPIC STRUCTURE

19. SARCOMERE STRUCTURAL AND FUNCTIONAL UNIT OF SKELETAL MUSCLE. EXTENDS BETWEEN TWO Z LINES.

20. ELECTRON MICROSCOPIC STUDY OF SARCOMERE Sarcomere consists of thread known as myofilaments . They are of two types:- ACTIN FILAMENT(THIN) MYOSIN FILAMENT(THICK)

21. Structure of Actin and Myosin

22. CONTRACTILE ELEMENTS OF MUSCLE Myosin filaments formed by myosin molecules Actin filaments are formed by three types of protein:- Actin Tropomyosin Troponin

23. MYOSIN FILAMENT Each myosin molecule made up of 6 polypeptide chain,2 heavy chains and 4 light chains. PORTION OF MYOSIN MOLECULE :- TAIL PORTION HEAD PORTION

24. MYOSIN MOLECULE Myosin molecule formed by two heavy chains and four light chains of polypeptides

25. ACTIN MOLECULE The major constituents of the thin actin filaments. Each actin molecule is called F- actin and it is the polymer of a small protein known as G- actin Actin molecules in the actin filament are arranged in the form of a double helix. Each F ­ actin molecule has an active site to which the myosin head is attached

26. TROPONIN FORMED BY THREE SUBUNITS:- TROPONIN I:- attached to F actin TROPONIN T:- attached to Tropomyosin TROPONIN C:- attached to calcium ions.

27. TROPOMYOSIN About 40 to 60 Tropomyosin molecules are situated along the double helix strand of actin filament. In relaxed condition of the muscle, the Tropomyosin molecules cover all the active sites of F ­ actin molecules.

28. OTHER PROTEINS OF MUSCLE :- ACTININ DESMIN NEBULIN TITIN DYSTROPHIN

29. SARCOTUBULAR SYSTEM System of membranous structures in the form of vesicles and tubules in the sarcoplasm of the muscle fibres Formed mainly by two types of structures: T ­tubules :- T ­tubules or transverse tubules are narrow tubules formed by the invagination of the sarcolemma L­ tubules or sarcoplasmic reticulum :- L­tubules or longitudinal tubules are the closed tubules that run in long axis of the muscle fiber

30. FUNCTION OF SARCOTUBULAR SYSTEM Function of T-Tubules responsible for rapid transmission of impulse in the form of action potential from sarcolemma to the myofibrils. Function of L-Tubules L-­tubules store a large quantity of calcium ions. When action potential reaches the cisternae of L- ­tubule, the calcium ions are released into the sarcoplasm .

31. Molecular basis of muscular contraction Includes three stages:- Excitation-contraction coupling Role of troponin and Tropomyosin Sliding Mechanism

32. EXCITATION CONTRACTION COUPLING Excitation-contraction coupling is the process that occurs in between the excitation and contraction of the muscle.

33. Role of Troponin and Tropomyosin

34. SLIDING MECHANISM

35. Components of Sarcomeres

36. Sliding Filament Model Actin myofilaments sliding over myosin to shorten sarcomeres Actin and myosin do not change length Shortening sarcomeres responsible for skeletal muscle contraction During relaxation, sarcomeres lengthen

37. SLIDING MECHANISM

38. Sarcomere Shortening

39. SEQUENCE OF MUSCLE RELAXATION:-

40. SPECIAL STAINS VAN GIESON – YELLOW MASSON TRICHOME - RED

41. PTAH - BLUE PAS – PALE PINK

42. METHENAMINE SILVER – PALE GREY H AND E – DEEP PINK

43. L.S STRIATED MUSCLE –H& E C.S OF STRAITED MUSCLE – H& E

44. GROWTH AND REGENERATION CELLS THAT FORM SKELETAL MUSCLE ARE CALLED MYOBLASTS SATELLITE CELLS SERVES AS A POTENTIAL SOURCE OF NEW MYOBLAST THAT ARE CAPABLE OF FUSING NEW MUSCLE FIBRE.

45. Smooth muscles Elongated spindle-shaped muscle 30um in length Non striated,involuntary Supplied by autonomic nerves system. MYOFIBRILS AND SARCOMERE ARE ABSENT.

46. Smooth Muscle Characteristics Not striated Dense bodies instead of Z disks as in skeletal muscle Have non contractile intermediate filaments Ca 2+ required to initiate contractions Types Visceral or unitary Function as a unit Multiunit Cells or groups of cells act as independent units

47. STRUCTURE IN WHICH SMOOTH MUSCLES ARE PRESENT

48. Functional Properties of Smooth Muscle Some visceral muscle exhibits autorhythmic contractions Tends to contract in response to sudden stretch but no to slow increase in length Exhibits relatively constant tension: Smooth muscle tone Amplitude of contraction remains constant although muscle length varies

49. Smooth Muscle Regulation Innervated by autonomic nervous system Neurotransmitter are acetylcholine and norepinephrine Hormones important as epinephrine and oxytocin Receptors present on plasma membrane which neurotransmitters or hormones bind determines response

50. CONTRACTILE PROTEINS ACTIN MYOSIN TROPOMYOSIN THICK AND THIN FILAMENTS Thick filaments formed by myosin molecule Thin filament formed by actin and Tropomyosin molecule.

51. SARCOTUBULAR SYSTEM T – Tubules are absent. L – tubules are poorly developed

52. TYPES OF SMOOTH MUSCLE :- SINGLE UNIT OR VISCERAL SMOOTH MUSCLE Fibres with interconnecting gap junction. Gap junctions allow rapid spread of action potential throughout the tissue. DISTRIBUTION OF SINGLE UNIT SMOOTH MUSCLE FIBERS Gastrointestinal organs Uterus Ureters Respiratory tract.

53. MULTIUNIT SMOOTH MUSCLE FIBERS :- MUSCLE FIBER WITHOUT INTERCONNECTING GAP JUNCTION . DISTRIBUTION OF MULTIUNIT SMOOTH MUSCLE FIBERS :- Ciliary muscle of eye Iris of the eye Nictitating membrane Arrector pili Smooth muscle of blood vessel and urinary bladder.

54. MOLECULAR BASIS OF SMOOTH MUSCLE CONTRACTION :- This process is called LATCH – BRIDGE mechanism.

55. CONTROL OF SMOOTH MUSCLE NERVOUS FACTOR:- Sympathetic and parasympathetic nerves control the activities. HUMORAL FACTOR:- Activity controlled by hormones , neurotransmitter and other humoral factor. HORMONES AND NEUROTRANSMITTER : acetyl choline , ADH, Adrenaline, noradrenaline , histamine. HUMORAL FACTORS CAUSES RELAXATION: Lack of oxygen, excess of carbon dioxide , lactic acid , excess of potassium ion , decrease in calcium ion.

56. Cardiac muscle The heart wall is made up of myocardium.

57. Cardiac muscle/myocardium Many similar structural and functional characteristics of skeletal and smooth muscles. Exhibits cross strations . Shorter muscle fibers. Shows branching pattern. One or two nuclei placed centrally Involuntary and contracts automatically like smooth muscle

58. FUNCTIONAL SYNCITIUM Darkly stained T lines across the fibers –intercalated discs Specialised cell junctions between the ends of adjacent muscle fibers. This cell junctions(gap junction and desmosomes ). Providing cytoplasmic continuity. Rapid trasmission of impluse . Contract simultaneously.

59. PURKINJE FIBRES The conducting system of the heart. Modified cardiac muscle fiber. Thicker ,larger, few myofilaments . Conduct stimuli faster (2-3m/s vs 0.6m/s). Seen beneath the endocardium .

60. Four properties of cardiac cells EXITABILITY: CONDUCTIVITY: CONTRACTILITY: RHYTHMICITY:

61. STRUCTURE EMBEDDED WITHIN SARCOPLASM :-

62. IHC MARKER FOR MUSCLES SMOOTH MUSCLE :- H.CAL DESMON,SMOOTH MUSCLE SPECIFIC ACTIN SKELETAL MUSCLE :- INTEGRIN β 1-d,FILAMIN –C (FLN-C)/ACTIN BINDING LIKE PROTEIN, ACTIN α -1 SKELETAL MUSCLE CARDIAC MUSCLE :- INTEGRIN β 1-d, ,FILAMIN –C (FLN-C)/ACTIN BINDING LIKE PROTEIN.

63. MUSCULAR DYSTROPHY Genetic disorder causes weakness in the muscle. Diagnosed by muscular biopsy. Individuals with MD donot produce dystrophin .

64. Duchenne’s muscular dystrophy Most common type. Caused by a defect with the gene that makes a protein – dystrophin . Without the protein, the muscles break down. And the person gradually becomes weaker. Symptoms:wasting of muscles,poor balance,limited range of movements.

65. Becker muscular dystrophy

66. Becker muscular dystrophy

67. REFERENCES TEXT BOOK OF HISTOLOGY-A PRACTICAL GUIDE-second edition , J P Gunasegaran . KRAUSE’S ESSENTIAL HUMAN HISTOLOGY FOR MEDICAL STUDENTS -Third Edition ,William J. Krause, Ph.D. HAM’S HISTOLOGY – Ninth edition ,David H. Cormack , Ph.D . WHEATHER’S FUNCTIONAL HISTOLOGY – 5 th Edition , Young ,Lowe ,Stevens ,Health .