The body wall of cucumbers is thick and well developed. It is similar to that of other echinoderms in consisting of a nonciliated epidermis, connective tissue dermis, circular and longitudinal muscles, and a ciliated peritoneum. It is unusual in that the longitudinal muscles are in five longitudinal bands and the ossicles are microscopic plates scattered in the dermis. Collagen fibers in the dermis can, under nervous control, be cross-linked with each other to form a rigid skeleton that can scarcely be cut with a scalpel. The gut is a simple tube extending from mouth to anus.
Gas exchange is via evaginations of the posterior gut.
Large branched tube feet encircle the mouth and are used for feeding. The blood vascular system is better developed than is typical in echinoderms and the coelom is large and spacious. The madereporite opens into the perivisceral coelom, rather than to the outside. Sea cucumbers are gonochoristic and have a single gonad opening to the exterior via a gonopore at the oral end. External Anatomy 1.