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acoelomates pseudocoelomates and coelomates

Acoelomates, Pseudocoelomates and Coelomates The following account would help to explain the above mentioned terms. Acoelomates In phylum Platyhelminthes there is no body cavity or coelom, and the mesoderm forms a loose, cellular tissue called mesenchyma or parenchyma which ills the space between the ectoderm and endoderm. It forms a packing around the internal organs of the animals to support and protect them. Such animals are called acoelomates (Fig. 10.3). In acoelomates the gut is sac-type and there is no special transport system. Only excretory system is developed for the transport of excretory products. This system consists of lame cells, excretory ducts and excretory pores. However the nervous system is well developed. Pseudocoelomates In Aschelminthes the space between the body wall and the digestive tube is called pseudocoelom (false body cavity). Pseudocoelom is not homologous to true coelom because: it is not lined by coelomic epithelium. It has no relation with the reproductive and excretory organs. It develops from the blastocoel of the embryo and it is bounded externally by the muscles and internally by the cuticle of the intestine. The animals having pseudocoelom are called pseudocoelomates Coelomates Coelom is cavity present between the body wall and the alimentary canal and is lined by mesoderm. The mesoderm splits into outer parietal layer which under lines the body wall and the visceral layer which covers the alimentary canal and the cavity between them is the true coelom. It is illed with luid called coelomic luid. The animals which possess coelom or true body cavity are called coelomates e.g. animals from annelids to chordates. In coelomates gut attains more complexity and neuro-sensory system is well developed along with excretory system, circulatory system, respiratory and reproductive systems. #visiblescience #mdcatbiology #alevelbiology #fscpart1 #acoelomatespseudocoelomatesandcoelomates