allantoic sac
the dilated portion of the allantois which becomes a part of the placenta in many mammals; in humans it becomes the urachus.

Medical dictionary. 2011.

Look at other dictionaries:

  • allantoic stalk — the slender tube interposed between the urogenital sinus and allantoic sac in the embryo; its intraembryonic part is the precursor of the urachus …   Medical dictionary

  • sac — 1. A pouch or bursa. SYN: saccus [TA]. SEE ALSO: sacculus. 2. An encysted abscess at the root of a tooth. 3. The capsule of a tumor, or envelope of a cyst. [L. saccus, a …   Medical dictionary

  • allantoic diverticulum — the sausage shaped endodermal sacculation that becomes the allantois; in humans it is an outpouching of the caudal wall of the yolk sac that becomes the urachus and remains throughout life as the median umbilical ligament. Called also allantoic… …   Medical dictionary

  • allantoic bladder — a membranous sac formed in amphibians as an outgrowth of the cloaca for the storage of urine …   Medical dictionary

  • allantoic — adj. pertaining to a sac like extraembryonic membrane which develops in certain animals (Zoology) …   English contemporary dictionary

  • allantois — noun A sac, having a number of functions, that develops in the alimentary canal of the embryos of mammals, birds and reptiles. Syn: allantoic sac, allantoid …   Wiktionary

  • Diverticulum — A small bulging sac pushing outward from the colon wall is a diverticulum. As a person ages, pressure within the large intestine (colon) causes pockets of tissue (sacs) that push out from the colon walls. The plural is diverticula. Diverticula… …   Medical dictionary

  • Cyst — A closed sac or capsule, usually filled with fluid or semisolid material. * * * 1. A bladder. 2. An abnormal sac containing gas, fluid, or a semisolid material, with a membranous lining. SEE ALSO: pseudocyst. [G. kystis, bladder] adventitious c.… …   Medical dictionary

  • allantois — A fetal membrane developing from the hindgut (or yolk sac, in humans). In humans it is vestigial; externally, in mammals, it contributes to the formation of the umbilical cord and placenta; in birds and reptiles, it lies close beneath the porous… …   Medical dictionary

  • animal development — Introduction  the processes that lead eventually to the formation of a new animal starting from cells derived from one or more parent individuals. Development thus occurs following the process by which a new generation of organisms is produced by …   Universalium

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