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The Muscular System

The Muscular System. Muscles are responsible for all types of body movement The sole function of muscle tissue is to contract or shorten. As it contracts, it causes movement, maintains posture, stabilizes joints, and generates heat Three basic muscle types are found in the body

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The Muscular System

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  1. The Muscular System • Muscles are responsible for all types of body movement • The sole function of muscle tissue is to contract or shorten. As it contracts, it causes movement, maintains posture, stabilizes joints, and generates heat • Three basic muscle types are found in the body • Skeletal muscle • Cardiac muscle • Smooth muscle

  2. Characteristics of Muscles • Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber) • Contraction of muscles is due to the movement of microfilaments • All muscles share some terminology • Prefixes myo and mys refer to “muscle” • Prefix sarco refers to “flesh”

  3. Comparison of Skeletal, Cardiac, and Smooth Muscles

  4. Comparison of Skeletal, Cardiac, and Smooth Muscles Table 6.1 (2 of 2)

  5. Smooth Muscle Characteristics • Lacks striations • Spindle-shaped cells • Single nucleus • Involuntary—no conscious control • Found mainly in the walls of hollow organs

  6. Smooth Muscle Characteristics Smooth muscle is found in the outer wall of the intestine (arrows) where it is typically arranged into inner circular and outer longitudinal layers. When the layers contract substances (food, urine, baby) are moved along internal pathway Figure 6.2a

  7. Peristalsis Alternating contractions of circular and longitudinal muscles move food along the digestive tract, a process known as peristalsis.

  8. In blood vessels, bundles of smooth muscle fibers encircle the arterial walls, constricting the vessels as the fibers contract. Smooth muscles in blood vessel produce constriction and dilation in response to change in core body and skin temperature.

  9. Cardiac Muscle Characteristics • Striations • Usually has a single nucleus • Branching cells • Joined to another muscle cell at an intercalated disc • Involuntary • Found only in the heart

  10. Cardiac Muscle Characteristics Spiral arrangement of cardiac muscle in the heart wall Figure 6.2b

  11. Skeletal Muscle Characteristics • Most are attached by tendons to bones • Cells are multinucleate • Striated—have visible banding • Voluntary—subject to conscious control

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