Smooth Muscle

As implied by the name, smooth muscle cells (fig. 1.9) do not have the striations characteristic of skeletal and cardiac muscle. Smooth muscle is found in the digestive tract, blood vessels,

Human Physiology Images

Dendrites

Cell body Supporting cells

Axon

Dendrites

Cell body Supporting cells

Axon

■ Figure 1.10 A photomicrograph of nerve tissue. A single neuron and numerous smaller supporting cells can be seen.

bronchioles (small air passages in the lungs), and in the ducts of the urinary and reproductive systems. Circular arrangements of smooth muscle in these organs produce constriction of the lumen (cavity) when the muscle cells contract. The digestive tract also contains longitudinally arranged layers of smooth muscle. The series of wavelike contractions of circular and longitudinal layers of muscle known as peristalsis pushes food from one end of the digestive tract to the other.

The three types of muscle tissue are discussed further in chapter 12.

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Essentials of Human Physiology

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