Skeletal Muscle

A. Muscle structure and filaments (Figure 1-8)

Sarcomere

I band

I band

Sarcomere

I band

I band

Z line

M line

Z line

H band

Z line

M line

Z line

H band

Myofibril

A band b

Terminal cisternae

Sarcoplasmic reticulum

Figure 1-8. Structure of the sarcomere In skeletal muscle. (A) Arrangement of thick and thin filaments. (B) Transverse tubules and sarcoplasmic reticulum (SR). (Adapted with permission from Bullock J, Boyle J III, Wang MB: Physiology, 2nd ed. Baltimore, Williams & Wilkins, 1991, p 29.)

I — Sarcolemmal membrane

Terminal cisternae

Sarcoplasmic reticulum

Figure 1-8. Structure of the sarcomere In skeletal muscle. (A) Arrangement of thick and thin filaments. (B) Transverse tubules and sarcoplasmic reticulum (SR). (Adapted with permission from Bullock J, Boyle J III, Wang MB: Physiology, 2nd ed. Baltimore, Williams & Wilkins, 1991, p 29.)

- Each muscle fiber is multinucleate and behaves as a single unit. It contains bundles of myofibrils, surrounded by SR and invaginated by transverse tubules (T tubules).

- Each myofibril contains interdigitating thick and thin filaments arranged longitudinally in sarcomeres.

- Repeating units of sarcomeres account for the unique banding pattern in striated muscle. A sarcomere runs from Z line to Z line.

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