Thececum (UK:caecum,pronounced/ˈsiːkəm/; pluralceca orUK:caeca,pronounced/ˈsiːkə/) is a pouch within theperitoneum that is considered to be the beginning of thelarge intestine.[1] It is typically located on the right side of the body (the same side of the body as theappendix, to which it is joined). The term stems from theLatincaecus, meaning "blind".
It receiveschyme from theileum, and connects to theascending colon of thelarge intestine. It is separated from the ileum by theileocecal valve (ICV), also called Bauhin's valve. It is also separated from thecolon by the cecocolic junction. While the cecum is usually intraperitoneal, the ascending colon isretroperitoneal.[2]
Inherbivores, the cecum stores food material where bacteria are able to break down thecellulose. In humans, the cecum is involved in absorption ofsalts andelectrolytes and lubricates the solid waste that passes into the large intestine.[3]
The cecum and appendix are derived from the bud of cecum that forms during week six in the midgut next to the apex of the umbilical herniation.[5] Specifically, the cecum and appendix are formed by the enlargement of the postarterial segment of the midgut loop. The proximal part of the bud grows rapidly to form the cecum. The lateral wall of the cecum grows much more rapidly than the medial wall, with the result that the point of attachment of theappendix comes to lie on the medial side.[citation needed] The cecum's position changes after the midgut rotates and the ascending colon elongates, and the accumulation of meconium inside the cecum may result in the latter's increased diameter.[5]
The termcecum comes from Latin(intestinum) caecum, literally 'blind intestine', in the sense 'blind gut' or 'cul de sac'.[6] It is a direct translation from Ancient Greekτυφλὸν (ἔντερον)typhlòn (énteron). Thus the inflammation of the cecum is called typhlitis.
The junction between the small intestine and the colon, called theileocecal valve, is so small in some animals that it was not considered to be a connection between the small and large intestines. During a dissection, the colon could be traced from therectum, to thesigmoid colon, through thedescending,transverse, andascending sections. The cecum is an end point for the colon with a dead-end portion terminating with theappendix.[8]
The connection between the end of the small intestine (ileum) and the start (as viewed from the perspective of food being processed) of the colon (cecum) is now clearly understood, and is called the ileocecal orifice. The connection between the end of the cecum and the beginning of the ascending colon is called the cecocolic orifice.
Gastric cecum of dissectedcockroach. Scale bar, 2 mm.
A cecum is present in mostamniote species, and also inlungfish, but not in any living species ofamphibian. Inreptiles, it is usually a single median structure, arising from the dorsal side of the large intestine. The ceca inbirds are often paired, with many exceptions; parrots, for example, do not have ceca, while others may have a single cecum or even two pairs, like thesecretarybird.[16]
Most mammalianherbivores have a relatively large cecum. In many species, it is considerably wider than the colon. For some herbivores such aslagomorphs (rabbits, hares, pikas), easily digestible food is processed in the gastrointestinal tract and expelled as regular feces. But in order to get nutrients out of hard-to-digest fiber, lagomorphs ferment fiber in the cecum and then expel the contents ascecotropes, which are reingested (cecotrophy). The cecotropes are then absorbed in the small intestine to utilize the nutrients.
In contrast, obligatecarnivores, whose diets contain little or no plant matter, have a reduced cecum, which is often partially or wholly replaced by theappendix.[17] Mammalian species which do not develop a cecum includeraccoons,[18]bears,[19] and thered panda.[20]Hyraxes, unlike other mammals, have two paired ceca.[17]
Many fish have a number of small outpockets, calledpyloric ceca, along their intestine; despite the name, they are nothomologous with the cecum of amniotes – their function is to increase the overall area of the digestive epithelium.[17] Some invertebrates, such as squid,[21] may also have structures with the same name, but these have no relationship with those of vertebrates.
^Stedman, Thomas (2000).Stedman's medical dictionary. Philadelphia: Lippincott Williams & Wilkins. p. 915.ISBN978-0-683-40007-6.OCLC42772946.large i[ntestine], the portion of the digestive tube extending from the ileocecal valve to the anus; it comprises the cecum, colon, rectum, and anal canal
^University of Glasgow. 2005.The normal gut flora. Available through web archive. Accessed May 22, 2008
^Beaugerie L, Petit JC (April 2004). "Microbial-gut interactions in health and disease. Antibiotic-associated diarrhoea".Best Pract Res Clin Gastroenterol.18 (2):337–52.doi:10.1016/j.bpg.2003.10.002.PMID15123074.
^abcRomer, Alfred Sherwood; Parsons, Thomas S. (1977).The Vertebrate Body. Philadelphia: Holt-Saunders International. pp. 353–54.ISBN978-0-03-910284-5.
