Physical characteristics

Ctenophores, or "comb bearers," are named for the characteristic eight rows of macrociliary plates that they all possess at some point during their life. The body consists of two tissue layers, the endodermis and the ectodermis, which en close a poorly differentiated gelatinous layer of acellular mesoglea. Ctenophores have a statocyst that consists of a pit of modified ciliated epithelium containing a calcareous sta-tolith. This statocyst is mechanically coupled to the ctene rows by four pairs of ciliary tracts and four sets of balancer cilia. The subectodermal nerve net is associated with this statocyst. Ctenophores lack the epithelial-muscle cells characteristic of cnidarians, but do have both smooth and striated muscle. The gastro-vascular system does have two openings, however secretions of material out of the anal pores is rare, with defecation of undigested material occurring primarily through the mouth. There is a complex network of circulatory canals that often form the basis for ctenophore taxonomy. The phylum Ctenophora is unique in the possession of specialized adhesive structures called colloblasts. These organelles are utilized to capture prey in an analogous fashion to the nematocysts in the Cnidaria, but the colloblast and ne-matocyst morphologies are very different. The atentaculate ctenophores lack colloblasts.

Essentials of Human Physiology

Essentials of Human Physiology

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.

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