IV. SKELETAL MUSCLE TISSUE
A. Gross Structure
1. Fascia (Connective Tissue)
Connective tissue grouping whole muscles, filling spaces, providing origins of muscles
2. Epimysium
Connective tissue around entire muscle
3. Fascicles
Cell bundles
4. Perimysium
Connective tissue around fascicles
5. Endomysium
Connective tissue around single muscle cell
6. Tendon
Muscle to bone (epimysium to periosteum)
7. Aponeurosis
Broad sheet like tendon
B. Microstructure
1. Myofiber
Muscle cell
a. Multinucleate, numerous mitochondria
b. No mitosis
c. Sarcolemma
Plasma membrane
d. Sarcoplasmic reticulum [terminal cisternae]
Calcium storage
e. Transverse (T) tubules
Sarcolemma to interior of cell
2. Myofibril(1u)
Attached to sarcolemma, responsible for contraction
a. I bands (isotropic)
b. A bands (anisotropic)
c. Z lines
d. Sarcomere
Functional unit of muscle contraction. Spans from one Z line to next.
3. Myofilaments
a. Thick (16nm)
1. Myosin
2. Cross bridges (actin binding site)
3. ATP binding site
b. Thin (6nm)
1. Actin
2. Tropomyosin
3. Troponin
Anchors tropomyosin to actin