3 types, skeletal muscle made of muscle fibers: which are syncitium..

1. MUSCULAR TISSUE
Dr Akhila V
senior Resident
Department of Anatomy
GMCT

2. MUSCULAR TISSUE
• Cells that are specialized to shorten in length
by contraction
• Myocytes / muscle fibers
• Contractile proteins: Actin & Myosin
• Cell organelles:
• Sarcolemma
• Sarcoplasm
• Sarcoplasmic reticulum
• Sarcosome
• Mesodermal exception: erector pili, iris
muscles, myoepitheliocytes

4. Types
SKELETAL MUSCLE SMOOTH MUSCLE CARDIAC MUS LE
In relation with limbs & body wall Relation to viscera Exclusively in the heart
Transverse striations present Transverse striations absent Transverse striations present
Voluntary Involuntary Involuntary
Somatic motor nerves Autonomic nerves Autonomic nerves

6. SKELETAL MUSCLE FIBER
• A syncytium
• Numerous elongated nuclei along the periphery
• Myofibrils
• Transverse striations:
A- band (Anisotropic)dArk
I - band (Isotropic) lIght
• Numerous mitochondria
• Glycogen rich
• Bundles/ fasciculi

7. Sarcoplasmic reticulum

8. CONNECTIVE TISSUE FRAMEWORK
• Epimysium
• Perimysium
• Endomysium

9. • Endomysium: around
each muscle fiber
• Perimysium: around
individual fasciculi
• Epimysium:
around entire muscle

10. L S

11. Ultrastructure of myofibrils
• Made of myofilaments
• Actin myofilament
• Myosin myofilament
• Alignment creates bands

13. Types of skeletal muscle
Red muscle fiber White muscle fiber
((Type 1 fibers/ slow twitch fibers)) ((Type 2 fibers/ fast twitch fibers))
Rich in myoglobin & cytochrome
Red in colour
Less myoglobin & cytochrome
White in colour
Narrow diameter
Less defined striations
Nuclei not always at periphery
Broader diameter
Well defined striations
Nuclei at periphery
More cytoplasm
More glycogen
More myofibrils
Less glycogen
Numerous mitochondria
SR less extensive
Few mitochondria
Extensive SR
Slow & continuous contraction
Not easily fatigued
Rapid contraction
Easily fatigued
Rich blood supply Poor blood supply
Eg: postural muscles Eg: extraocular muscles & flight muscles in birds

14. Blood vessels and lymphatics of skeletal muscle:
• Neurovascular hilus
• Arterial plexus  in epimysium, perimysium
• Veins - accompany arteries
• Lymphatics plexus  also in epimysium, perimysium
Innervation of skeletal muscle:
• Neurovascular hilus

15. Motor unit
• A single alpha motor neuron
with its supplied muscle fibres.
• Because of repeated branching
• Number of fibres- varies

16. Motor end plate
• The junction between a muscle
fibre and the nerve terminal that
supplies
• Nerve loses its myelin sheath
and breaks up into number of
branches

17. SKELETAL MUSCLE – L.S
striations
Peripheral nucleus
Muscle fiber
LS

18. Skeletal Muscle- C.S
epimysium
perimysium
endomysium
Muscle fiber
fascicle
nucleus
CS

19. SMOOTH MUSCLE
• Non-striated/ involuntary/ plain
muscle
• Myocytes:
• long spindle shaped cells
• broad central part and tapering ends
• Form bundles/ fasciculi layers
• Gap junctions
• Delicate myofilaments- irregularly
arranged
• Caveolae – calcium storage

20. Distribution
• Walls of hollow viscera:
• stomach
• intestine
• urinary bladder
• uterus
• Walls of narrow tube :
• arteries, veins, bronchi, ureters, deferent ducts, uterine tubes, ducts of
several glands
• Pupillary Muscles
• Constrictor pupillae
• Dilator pupillae
• Errector pili muscle

21. Contraction of smooth muscle:
• Smooth muscle need very little ATP for contraction
• caveolae - regulation of flow of calcium ions
Innervation: autonomic nerves
Blood vessels and lymphatics: density is much less than in skeletal
muscle

22. Smooth muscle
nucleus
Muscle fiber
LS
CS

23. CARDIAC MUSCLE
Similarities with skeletal muscle
• Elongated muscle fibers
• Transverse striations
• A,I,Z & H bands
• Connective tissue framework
• Capillary network
• Actin and myosin filaments
• Cell organelles

24. Differences with skeletal muscle
• Muscle fibers – branch and anastomose
• Not a syncytium
• Central nucleus/ abundant sarcoplasm/numerous mitochondria
• Striations are not as distinct
• Intercalated discs
• Involuntary

26. Clinical Correlation
• Myasthenia gravis: Autoimmune disorder, AChR in the motor
endplates of the muscle are damaged
• Skeletal muscle tumours
Rhabdomyoma
Rhabdomyosarcoma
• Excessive activity of smooth muscle:
Bronchial asthma
Intestinal colic/ renal colic/ biliary colic

27. Characteristics Skeletal muscle Cardiac muscle Smooth muscle
Muscle fiber Long, cylindrical &
branched
Short, narrow & branched Fusiform/ spindle shaped
& unbranched
Control Voluntary Involuntary Involuntary
Location Muscle of skeleton,
tongue, esophagus,
diaphragm
Heart, pulmonary veins,
superior & inferior vena
cavae
Vessels, organs & viscera
Striations Present (well defined) Present (poorly defined) Absent
Nuclei Multiple, flat, located at
periphery
Single, oval, present in
centre
Single, oval, present in
centre
Sarcoplasmic reticulum Present ( form triads) Present ( form diads) Absent
Intercalated disc Absent Present Absent
Regeneration after injury Seen (limited) Not seen seen

28. Cardiac muscle
nucleus
Intercalated disc

29. THANK YOU