muscle

(mŭs′ĕl)

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[L. musculus, diminutive of mus, mouse]
A type of tissue composed of contractile cells. Each muscle cell is filled with parallel actin and myosin filaments. When activated by an internal release of calcium, the filaments use the energy in adenosine triphosphate to crawl along each other in opposite directions. This movement shortens the length of the cell, which then contracts.
The three classes of myocytes (muscle cells) are skeletal (striated), cardiac (striated), and smooth; most human muscle is skeletal. A typical muscle has a central portion (the belly) and two or more attachment ends with tendons. The more stationary of the attachments is called the origin; the more movable attachment is called the insertion.
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SELECTED MUSCLES OF THE BODY
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MUSCLE FIBER
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MORPHOLOGICAL FORMS OF MUSCLE

Comparison of Properties of Three Types of Muscle
SmoothCardiacStriated
SynonymsInvoluntaryMyocardialVoluntary
NonstriatedSkeletal
Visceral
Fibers
 Length (in/m)50-20025,000
 Thickness (in/m) 4-8   75
 ShapeSpindlesCylinders
 MarkingsNo striationStriationMarked striation
NucleiSingleSingleMultiple
Effects of cutting related nerveSlightRegulation of heart rate is lostComplete paralysis

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