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longitudinal muscle
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Diagram showing three shapes of a wormlike soft-bodied animal: A is short and round for longitudinal muscle contraction, B is long and thin for circular muscle contraction, and C is curved for localized longitudinal muscle contraction.
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longitudinal muscle

anatomy
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Diagram showing three shapes of a wormlike soft-bodied animal: A is short and round for longitudinal muscle contraction, B is long and thin for circular muscle contraction, and C is curved for localized longitudinal muscle contraction.
changes in body form in wormlike soft-bodied animals Figure 5: Changes in body form in wormlike soft-bodied animals. (A) The longitudinal muscle contracting. (B) The circular muscle contracting. (C) The longitudinal muscle above contracting while the circular muscles maintain a constant length, stretching the longitudinal muscles below.

Longitudinal muscles are a type of muscle fiber that runs lengthwise along the body. In soft-bodied animals like worms, these muscles work antagonistically with circular muscles. When longitudinal muscles contract, the body shortens and widens. Conversely, when circular muscles contract, the body lengthens and thins. This interplay allows for movement such as crawling and burrowing. In some animals, like roundworms, only longitudinal muscles are present, and their contraction causes bending due to the body's rigid outer layer, the cuticle.12

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  1. muscle - Muscle in soft animals
  2. muscle - Worms

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