11.12.
2014
Muscular Tissue
Dr. Archana Rani
Associate Professor
Department of Anatomy
KGMU UP, Lucknow
What is Muscle Tissue?
• Composed of cells that are highly specialized
to shorten in length by contractility.
• Made up of cells that are called myocytes.
• Elongated in one direction (muscle fibres).
• Histologically, it is of 3 types:
(i) Skeletal muscle
(ii) Cardiac muscle
(iii) Smooth muscle
Skeletal Muscle
• Striated or voluntary muscle
• Present mainly in limbs and in relation to body
wall
• Supplied by somatic division of nervous system
• Formed by fusion of multiple myoblasts during
embryonic life
• Motor end plate
• Mostly originate from somatic mesoderm
Connective tissue frame work
Microscopic structure of Skeletal Muscle
• Fibres are arranged parallel to each other
• Basic unit is long, cylindrical fiber
• Alternate dark & light bands (cross-striations)
• Multinucleated, placed peripherally beneath
the sarcolemma
• Myofibrils: contractile elements
• Sarcomere: fundamental contractile unit
• Myofilaments: contain thick (myosin) and thin
(actin) filaments
Skeletal Muscle
• Each thick filament is surrounded by 6 thin
filaments in hexagonal fashion
• Accessory proteins necessary for proper
contraction: Titin, alpha actinin, nebulin,
tropomodulin, dystrophin
• Nerve supply:
Motor fibres
Sensory fibres
Section of Skeletal muscle
LS
TS
Longitudinal Section of Skeletal muscle
Motor Unit
Clinical Application
• Duchenne Muscular Dystrophy (DMD)
• Rigor Mortis
• Myasthenia Gravis
• Neurotoxins
• Hypertrophy and Atrophy
• Regeneration
Cardiac Muscle
• Striated and involuntary
• Present exclusively in heart
• Originates in splanchnopleuric mesoderm
• Supplied by ANS (sympathetic &
parasympathetic)
Microscopic structure of Cardiac Muscle
• Consists of long and thick branching muscle
fibres (may appear as Y shaped)
• Intercalated discs
• Centrally placed single oval nucleus
• Faint transverse striations
• A & I bands along with Z discs present
Section of Cardiac muscle
LS TS
Cardiac Muscle
Clinical Application
Hypertrophy can occur in cases of increased
blood pressure
Smooth Muscle
• Non-striated
• Supplied by ANS
• Present in GIT, walls of blood vessels, urinary
bladder, ureter, uterus, uterine tube, arrector
pili muscle (of hair follicles) etc.
Microscopic structure of Smooth Muscle
• Elongated spindle shaped fibres
• Centrally placed single elongated nucleus
• Adjacent cells are in contact with each other
through gap junctions
• Absence of striations
Smooth Muscle
Clinical Application
Regeneration capacity present
(applied in restenosis of vessel following
coronary angioplasty)
References
1. diFiore’s Atlas of Histology with functional
Correlations, 12th Edition.
2. Essentials of Anatomy for Dentistry Students.
DR Singh, 1st Edition.
3. Textbook of Histology. GP Pal, 3rd Edition.
MCQ
• Unbranched cylindrical shaped fiber is a
feature of:
1. Smooth muscle
2. Skeletal muscle
3. Cardiac muscle
4. None of the above
MCQ
• All of the following are microscopic features of
cardiac muscle except:
1. Intercalated discs
2. Prominent transverse striations
3. Branched cylindrical fibres
4. Single nucleus in each myocyte
MCQ
• Sarcomere is an area between:
1. Two adjacent Z lines
2. Two adjacent H bands
3. Two adjacent M lines
4. Two adjacent I bands
MCQ
• All of the following are microscopic features of
smooth muscle except:
1. Spindle shaped fibres
2. Single nucleus placed centrally
3. Prominent transverse striations
4. Gap junctions
MCQ
• Property of regeneration is not seen in:
1. Smooth muscle
2. Skeletal muscle
3. Cardiac muscle
4. All of the above
