Phylum Echinodermata Class Ophiuroidea Number of families 16
Small- to medium-size echinoderms with a flattened disk often covered with a series of scales, granules and small spines; usually five long thin (in comparison with the disk) articulated arms that break off easily; a row of papillae (small nipple-shaped structures) known as the arm comb near the base of each arm; lower surface of the disk containing a central mouth leading to the stomach pouch; mouth divided by five jaws
Photo: The snake star (Pectinura maculata) is an unusually large and mobile species. It is carnivorous, and has scales, not bristles. (Photo by ©David Hall/Photo Researchers, Inc. Reproduced by permission.)
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.