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Even in the marsupials that have one, the cloaca is partially subdivided into separate regions for the anus and urethra. Diagrams to illustrate the changes in the cloaca in mammals during development. A, early embryonic stage, showing the cloaca receiving the urinary bladder, the rectum, and the Wolffian duct, as in non-therian vertebrates.
In some organisms, including monotremes, [2] birds and some fish, discharge from the urological, digestive, and reproductive systems empty into a common sac called the cloaca. In most mammals , these three systems are more separated.
The mesonephric duct, also known as the Wolffian duct, archinephric duct, Leydig's duct or nephric duct, is a paired organ that develops in the early stages of embryonic development in humans and other mammals. It is an important structure that plays a critical role in the formation of male reproductive organs.
[4] The pond loach is able to respond to the periodic drying in their native habitats by burrowing into the mud and exchanging gas through the posterior end of their alimentary canal. [5] [6] Studies have shown that mammals are capable of performing intestinal respiration to a limited degree in a laboratory setting. [1]
The cloaca (pl.: cloacae) is a structure in the development of the urinary and reproductive organs.. The hind-gut is at first prolonged backward into the body-stalk as the tube of the allantois; but, with the growth and flexure of the tail-end of the embryo, the body-stalk, with its contained allantoic tube, is carried forward to the ventral aspect of the body, and consequently a bend is ...
[2]: 124–125 Male mammals, reptiles, and certain other vertebrates transfer sperm into the female's vagina or cloaca through an intromittent organ during copulation. [3] [4] [5] In most birds, the cloacal kiss is used, the two animals pressing their cloacas together while transferring sperm. [6]
In monotremes, the ureters open into the urogenital sinus, which is connected to the urinary bladder and cloaca, [65] and urine is excreted into the cloaca instead of the urethra. [66] [65] Structurally, kidneys vary between mammals. [67] Which structural type a particular species will have depends mainly on the body mass of the species. [68]
As the human embryo grows and caudal folding continues, the urorectal septum divides the cloaca into a ventral urogenital sinus and dorsal anorectal canal. Before the urorectal septum has an opportunity to fuse with the cloacal membrane, the membrane ruptures, exposing the urogenital sinus and dorsal anorectal canal to the exterior.