NSCI 1403 Lecture Notes - Lecture 23: Vomer, Cellular Respiration, Sarcolemma
27 Dec 2016
School
Department
Course
Professor
Document Summary
Three types of skeletons occur in the animal kingdom. A hydrostatic skeleton occurs in cnidarians, flatworms, roundworms and annelids. An exoskeleton is found in mollusks and arthropods, respectively. An endoskeleton is found in sponges, echinoderms, and vertebrates. A fluid filled gastrovascular cavity or coelom can act as a hydrostatic skeleton. It offers support and resistance to the contraction of muscles for motility. Animals with exoskeletons or endoskeletons move selected body parts by means of muscular hydrostats, i. e. , fluid contained within certain muscle fibers assists movement of that part. Mollusks have exoskeletons that are predominantly calcium carbonate (caco3). Insects and crustacea have jointed exoskeletons composed of chitin, a strong, flexible, nitrogenous polysaccharide. The exoskeleton provides protection against damage from enemies and also keeps tissues from drying out. Although stiffness provides support for muscles, the exoskeleton is not as strong as an endoskeleton. The chitinous exoskeleton of arthropods is jointed and moveable.
