Anus
| Anus | |
|---|---|
Superficial inguinal lymph nodes | |
| Identifiers | |
| Latin | anus |
| TA98 | A05.7.05.013 |
| TA2 | 3022 |
| Anatomical terminology] | |
In
bowel), i.e. the opposite end from the mouth. Its function is to facilitate the expulsion of wastes that remain after digestion
.
Bowel contents that pass through the anus include the gaseous
muscular sphincters, and failure to stop unwanted passages results in fecal incontinence
.
another for both urination and reproduction
, although the channels flowing to that orifice are almost completely separate.
The development of the anus was an important stage in the evolution of multicellular animals. It appears to have happened at least twice, following different paths in
arthropods
, which are composed of fused, specialized segments.
In comb jellies, there are species with one and sometimes two permanent anuses, species like the warty comb jelly grows an anus, which then disappear when it is no longer needed.[4]
Development
In animals at least as complex as an
gut. In deuterostomes, the original dent becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. The protostomes were so named because it was thought that in their embryos the dent formed the mouth first (proto– meaning "first") and the anus was formed later at the opening made by the other end of the gut. Research from 2001 shows the edges of the dent close up in the middles of protosomes, leaving openings at the ends which become the mouths and anuses.[5]
See also
The dictionary definition of anus at Wiktionary- Anal canal – Functional segment of the large intestine
- Anorectal manometry – Medical functional test of the anus and rectum
- Imperforate anus – Birth defect of malformed rectum
References
- ^ Helms, Doris R.; Helms, Carl W.; Kosinski, Robert J.; Cummings, John C. (1997). Biology in the Laboratory With BioBytes 3.1 CD-ROM. W. H. Freeman. p. 36-12.
- ISBN 978-0-520-22149-9.
- JSTOR 4010364. Archived from the originalon 2013-05-11. Retrieved 2009-04-24.
- ^ What is a warty comb jelly? | BBC Science Focus Magazine
- S2CID 4406268.
External links
Media related to Anus at Wikimedia Commons
