Histology of Muscle What is muscle Specialized cells

Histology of Muscle

What is muscle? Specialized cells –high degree of contractility and excitability. Cells in muscle tissue-Myocytes. Basically referred as Muscle fibre. Classification : Ø Skeletal Ø Cardiac Ø Smooth muscle.

Skeletal muscle Mainly present in relation with bones. Features : • Voluntary • Striated • Somatic nerve supply

Connective tissue framework

Microscopic structure üLong cylindrical fiberupto 30 cm. üFibers are arranged parallel to one another. üDiameter-0. 1 mm üSarcolemma üSarcoplasm üNuclei üMyofibril üOrganellesgolgi, mitochondria, ER.

Contd…. o y M f l i r ib

Cardiac muscle ü ü ü Present exclusively in heart. Features: Involuntary Striated Innervation-autonomic nerves.

Microscopic features ü ü ü Long and thick muscle fibers-50 -100 micrometer. Diameter-15 micrometer thickness. Each cardiac myocyte joined to one another-junctional specialization, Intercalated disc. ü ü Centrally placed single oval nucleus. Like skeletal muscle, shows striations-not prominent as it has few myofibrils, sarcoplasm is abundant.

Contd. . NUCLEUS INTERCALATED DISC

Smooth muscle q q ü ü ü Present in the eye, walls of vessels, respiratory tubes, digestive tubes, urinary organs, reproductive organs. Features: Nonstriated Involuntary Innervation-autonomic nerves.

Microscopic features o o o Elongated spindle shaped(fusiform) cells. Length-15 -500 micrometer. Diameter-3 -10 micrometer. Cells are arranged in bundles. Sarcolemma Sarcoplasm-eosinophilic because of contractile element(actin&myosin).

Contd…

Characteristics Skeletal muscle 1. Location Skeletal bones(usually) Heart Hollow viscera, trachea, bron chi… 2. Fiber Shape Unbranched cylindrical Spindle shaped 3. Nucleus Cardiac muscle Branched cylindrical Smooth muscle Multinucleated, peripher Single, center y Faint Prominent Single, center. 5. Connective tissue Organised to form endo, epi and perimysium. Only endomysium. 6. Junction between fibres Not seen Intercalateddisc, des mosomes, gap junction. Gap junctions (single unit) 7. Nervous control Innervated by somatic nerves By autonomic nerves 8. Autorhythmici ty No Proliferation-satellite No No In smooth muscles of viscera 4. Striations Not seen.