Sea Cucumber
The pharynx lies behind the mouth and is surrounded by a ring of ten calcareous (containing calcium carbonate; chalky) plates. In sea cucumbers, this is the only substantial part of the skeleton, and it forms the point of attachment for muscles that can retract the tentacles into the body for safety as for the main muscles of the body wall. Many species possess an oesophagus and stomach, but in some sea cucumber, the pharynx opens directly into the intestine. The intestine is typically long and coiled, and loops through the body three times before terminating in a cloacal chamber (is the posterior opening that serves as the only opening for the intestinal, reproductive, and urinary tracts of certain animal species.), or directly as the anus.
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