Muscular System

Closely tied functionally to the exoskeleton is the main muscular system. All muscles attach to the integument internally and provide motion to the arthropod body in all its varied actions. They never form a body wall plexus but lie in bundles running between insertions. The latter may be broad or attenuated, cover extensive areas on sclerites, or fasten to invaginated extensions of the latter, the apodemes. The latter, when long and slender, are tendonlike but are histologically unlike vertebrate connective tissue, which is virtually absent in insects and their arthropod relatives. Visceral muscles, as circular, oblique, or longitudinal bands, are confined to the walls of the digestive tract and ducts of the reproductive system. In insects and their relatives, all muscle tissue is striated, whether skeletal or visceral.

Physiologically, insect muscle tissue (Ush-erwood 1975) is basically the same as that of vertebrates, although it (apparently) is

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