Microscopic Anatomy of Muscle

Fascicle

bundle of muscle fibers

Fascicle pic

Muscle fiber

Muscle cell

Muscle fiber pic

Myofibril

contractile organelles found in the cytoplasm of muscle cells; contain many myofilaments

Myofibril pic

Myofilaments

The contractile proteins actin and myosin

Myofilaments pic

Epimysium

Connective tissue membrane that covers the entire muscle

Epimysium pic

Perimysium

Connective tissue membrane that surrounds fascicles

Perimysium pic

Endomysium

Connective tissue membrane that surrounds a muscle fiber

Endomysium pic

Sarcolemma

Plasma membrane of a muscle fiber

Sarcolemma pic

Sarcoplasmic Reticulum

Network of tubes surrounding each muscle fiber

Sarcoplasmic Reticulum pic

Terminal cisternae

Enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules; calcium reservoir

Terminal cisternae pic

Transverse Tubules

Pass along nerve impulse throughout muscle fiber; house motor nerves

Transverse Tubules pic

Sarcomere

basic contractile unit of muscle

Sarcomere pic

Myosin

Thick filament; contains binding sites for ATP and Actin

Myosin pic

Actin

Thin filament; contains active site for myosin attachment

Actin pic

C

Troponin

Contains a binding site for calcium ions (SFM)

Troponin pic

B

Tropomyosin

Strand that covers the active sites on a thin filament

Tropomyosin pic

A

Cross Bridge

Term used when a myosin head attaches to an active site

I-Band pic

D

A-Band pic

E

Z-Line pic

C

Zone of overlap

A