GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms: spiny-skinned animals that lack body segmentation but have radial symmetry (usually five g y y ( y part) and an internal skeleton.

Detailed explanation-2: -Echinodermata have unsegmented radially symmetrical body.

Detailed explanation-3: -Characteristics of Echinoderms Echinoderms are characterized by radial symmetry, several arms (5 or more, mostly grouped 2 left-1 middle-2 right) radiating from a central body (= pentamerous). The body actually consists of five equal segments, each containing a duplicate set of various internal organs.

Detailed explanation-4: -Type of Body Plan: Their body has no segmentation but this doesn’t mean it doesn’t have repetition. For example, though a starfish is not segmented, it still contains the same organs in every appendage. Number of body layers: Three body layers: ectoderm, mesoderm and endoderm.

Detailed explanation-5: -Although they may appear very different, echinoderms all have two major defining characteristics that set them apart from all other animals: a water vascular system and five-sided radial symmetry. The water vascular system is a complex series of canals running through an echinoderm’s body (Fig. 3.84).