Skeletal Muscle

Skeletal muscle may be defined as voluntary striated muscle that is usually attached to one or more bones. A typical skeletal muscle cell is about 100 ^m in diameter and 3 cm long; some are as thick as 500 ^m and as long as 30 cm. Because of their extraordinary length, skeletal muscle cells are usually called muscle fibers or myofibers. A skeletal muscle fiber exhibits alternating light and dark transverse bands, or striations, that reflect the overlapping arrangement of the internal contractile proteins (fig. 11.1). Skeletal muscle is called voluntary because it is usually subject to conscious control. The other types of muscle are involuntary (not usually under conscious control), and they are never attached to bones.

Recall from chapter 10 that a skeletal muscle is composed not only of muscular tissue, but also of fibrous connective tissue: the endomysium that surrounds each muscle fiber, the perimysium that bundles muscle fibers together into fascicles, and the epimysium that encloses the entire muscle. These connective tissues are continuous with the collagen fibers of tendons and those, in turn,

Figure 11.1 Skeletal Muscle Fibers. Note the striations.

Saladin: Anatomy & I 11. Muscular Tissue I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 11 Muscular Tissue 409

with the collagen of the bone matrix. Thus, when a muscle fiber contracts, it pulls on these collagen fibers and moves a bone.

Collagen is not excitable or contractile, but it is somewhat extensible and elastic. It stretches slightly under tension and recoils when released. Because of this elasticity and because the connective tissue components are connected to each other in a linear series, the connective tissues are called the series-elastic components of a muscle. Their elasticity helps to return muscles to their resting lengths when contraction ceases. Elastic recoil of the tendons adds significantly to the power output and efficiency of the muscles.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

  1. Define responsiveness, conductivity, contractility, extensibility, and elasticity. State why each of these properties is necessary for muscle function.
  2. How is skeletal muscle different from the other types of muscle?
  3. Why would the skeletal muscles perform poorly without their series-elastic components?

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  • gorbulas gardner
    Why would the skeletal muscles perform poorly without their series elastic compenents?
    7 years ago
  • landolfo napolitano
    Why would skeletal muscle perform poorly without their serieselastic components?
    7 years ago
  • hamfast
    Why wpuld the skeletal muscles perform poorly without?
    7 years ago
    Why would the skeletal muscles perform poorly without their serieselastic components?
    7 years ago

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