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Muscle Anatomy Picture
Muscle Anatomy
Muscle is composed of muscle cells (sometimes known as "muscle
fibers"). Within the cells are myofibrils; myofibrils contain sarcomeres, which
are composed of actin and myosin. Individual muscle cells are lined with
endomysium. Muscle cells are bound together by perimysium into bundles called
fascicles; the bundles are then grouped together to form muscle, which is lined
by epimysium. Muscle spindles are distributed throughout the muscles and provide
sensory feedback information to the central nervous system.
Skeletal muscle is arranged in discrete groups, examples of which include the
biceps brachii. It is connected by tendons to processes of the skeleton. In
contrast, smooth muscle occurs at various scales in almost every organ, from the
skin (in which it controls erection of body hair) to the blood vessels and
digestive tract (in which it controls the caliber of a lumen and peristalsis).
There are approximately 650 skeletal muscles in the human body (see list of
muscles of the human body). Contrary to popular belief, the number of muscle
fibers cannot be increased through exercise; instead the muscle cells simply get
bigger.
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