Intestinal Neoplasia Model Essay examples -- Biology,

The mammalian intestinal tract is structurally a tube that is divided into two segments: the small and large intestine. The inner wall consists of a simple epithelium called mucosa, which is responsible for the processing and absorption of nutrients (Sancho et al., 2003; Barker et al., 2008). The small intestine epithelium is folded into finger-like protrusions, called villi, directed toward the lumen; the valleys are invaginations into the sub-mucosa and are known as the crypts. In the large intestine, the mucosa lacks villi, and the crypts invaginate deep into the sub-mucosa. There are four distinctive, differentiated cell types in the mucosa to mediate the functions of the intestinal epithelium: enterocyte (EC), goblet cells (GC), enteroendocrine (EE), and Paneth cells (PC) (Radtke and Clevers, 2005; Barker et al., 2008). ECs are absorptive, and the others have secretory function. The epithelium renews its cells after every 4-5 days and is fueled by proliferative stem cells residi ng at the bottom of the crypt. In mammals, swallowed food passes through the esophagus to the stomach, where food accumulates and digestion proceeds; it then moves to the small intestine for nutrient absorption and later to the large intestine for further nutrient, water and electrolyte absorption. Finally, it reaches the rectum and anus for excretion (Thompson and Malagelada, 1981). Like mammalian intestine, Drosophila intestines also have similar tissue architecture and physiological function (Rubin, 2007). Developmentally, both the mammalian gut and Drosophila midgut are of endothelial in origin (Kedinger et al., 1987; Tepass and Hartenstein 1994). They comprise an epithelial monolayer of columnar or cuboidal cells called enterocytes. To maximize i... ...gle (E blast cell) lineage, is made of 20 cells arranged to form a tube with a central lumen. Each of these cell pairs forms an intestinal ring (II-IX int-rings). The most anterior intestinal ring (int ring I), is made of four cells. The apical surfaces of the intestinal cells carry numerous microvilli. In C. elegans, intestine carries out multiple functions that are executed by distinct organs of higher eukaryotes. The primary function of intestinal cells seems to be digestive since they secrete digestive enzymes (e. g. cysteine protease, endodeoxyribonuclease) into the lumen and take up processed material and nutrients. Intestine also seems to be a large storage organ since it contains a large number of assorted storage granules (White J., 1988)). The intestinal contents are excreted to the outside via a rectal valve that connects the gut to the rectum and anus.