1) Muscular tissue is composed of three main types - skeletal, smooth, and cardiac muscle. Skeletal muscle is striated and voluntary, attaching to bones, while smooth muscle is involuntary and not striated, found in organs and blood vessels. Cardiac muscle is striated and involuntary, unique to the heart. 2) All muscle types contain bundles of proteins called myofilaments that slide past each other to cause contraction. Skeletal muscle contains sarcomeres with overlapping actin and myosin filaments. Smooth muscle lacks sarcomeres but contains dense bodies. Cardiac muscle contains intercalated discs allowing synchronized contraction. 3) Contraction is initiated by calcium release from the sarcoplasmic retic

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

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

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

6. Muscle tissue

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

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

12. 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

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

14. 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

15. 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)

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

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

19. 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

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

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

22. Parts of a Muscle

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

24. MYOFIBRIL & ITS MICROSCOPIC
STRUCTURE

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

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

27. Structure of Actin and Myosin

28. CONTRACTILE ELEMENTS OF MUSCLE
• Myosin filaments
formed by myosin
molecules
• Actin filaments are
formed by three types
of protein:-
I. Actin
II. Tropomyosin
III.Troponin

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

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

31. 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

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

33. 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.

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

35. 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:
1. T tubules :-T tubules or
transverse tubules are narrow
tubules formed by the
invagination of the sarcolemma
2. L tubules or sarcoplasmic
reticulum:-Ltubules or
longitudinal tubules are the
closed tubules that run in long
axis of the muscle fiber

36. 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.

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

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

39. Role of Troponin and Tropomyosin

40. SLIDING MECHANISM

41. Components of Sarcomeres

42. 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

43. SLIDING MECHANISM

44. Sarcomere Shortening

45. SEQUENCE OF MUSCLE RELAXATION:-

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

47. PTAH - BLUE PAS – PALE PINK

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

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

50. 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.

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

52. Smooth Muscle
• Characteristics
– Not striated
– Dense bodies instead of Z disks as in skeletal muscle
• Have non contractile intermediate filaments
– Ca2+ required to initiate contractions
• Types
– Visceral or unitary
• Function as a unit
– Multiunit
• Cells or groups of cells act as independent units

53. STRUCTURE IN WHICH SMOOTH
MUSCLES ARE PRESENT

54. 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

55. 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

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

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

58. 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.

59. 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.

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

61. 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.

63. Cardiac muscle
• The heart wall is made
up of myocardium.

64. 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

66. 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.

67. 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.

68. Four properties of cardiac cells
• EXITABILITY:
• CONDUCTIVITY:
• CONTRACTILITY:
• RHYTHMICITY:

69. STRUCTURE EMBEDDED WITHIN
SARCOPLASM :-

71. IHC MARKER FOR MUSCLES
• SMOOTH MUSCLE:- H.CAL DESMON,SMOOTH
MUSCLE SPECIFIC ACTIN
• SKELETAL MUSCLE :- INTEGRIN β1-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.

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

74. 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.

77. Becker muscular dystrophy

78. Becker muscular dystrophy

83. 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 – 5th Edition ,
Young ,Lowe ,Stevens ,Health .