Cloaca

Source: Wikipedia, the free encyclopedia.
For other uses, see Cloaca (disambiguation).
Cloaca of a red-tailed hawk

A cloaca (

placental mammals, which have two or three separate orifices for evacuation and reproduction. Excretory openings with analogous purpose in some invertebrates are also sometimes called cloacae. Mating through the cloaca is called cloacal copulation
and cloacal kissing.

The cloacal region is also often associated with a secretory organ, the cloacal gland, which has been implicated in the scent-marking behavior of some reptiles,[1] marsupials,[2] amphibians, and monotremes.[3]

Etymology

The word is from the Latin verb cluo, "(I) cleanse", thus the noun cloaca, "sewer, drain".[4][5][6]

Birds

See also: Bird anatomy § Reproductive and urogenital systems
Cloaca of a female bird
Cloaca of a male bird
A roseate spoonbill excreting urine in flight

Birds reproduce using their cloaca; this occurs during a cloacal kiss in most birds.

phallus.[9]

One study[10] has looked into birds that use their cloaca for cooling.[11]

The cloaca in birds may also be referred to as the vent. Among falconers, the word vent is also a verb meaning "to defecate".

Fish

Among fish, a true cloaca is present only in

ray-finned fishes, part of the cloaca remains in the adult to receive the urinary and reproductive ducts, although the anus always opens separately. In chimaeras and most teleosts, however, all three openings are entirely separated.[12]

Mammals

With a few exceptions noted below, mammals have no cloaca. Even in the marsupials that have one, the cloaca is partially subdivided into separate regions for the anus and urethra.

urinary bladder, Wolffian ducts, and ureters, and into a dorsal part which receives the rectum. C, further progress of the fold, dividing the cloaca into urogenital sinus and rectum; the ureter has separated from the Wolffian duct and is shifting anteriorly. D, completion of the fold, showing complete separation of the cloaca into ventral urogenital sinus and dorsal rectum.[13]

Monotremes

The monotremes (egg-laying mammals) possess a true cloaca.[14]

Marsupials

Further information: Marsupial § Reproductive system
Cloacal opening in an Australian brushtail possum

In

mammals
.

Unlike other marsupials, marsupial moles have a true cloaca.[15] This fact has been used to argue that they are not marsupials.[16][17][unreliable source?]

Placentals

Most adult

penile urethra, while in females, it develops into the vestibule or urogenital sinus that receives the urethra and vagina.[12][18] However, some placental mammals retain a cloaca as adults: those are the tenrecs and golden moles (small mammals native to Africa), as well as some shrews.[19]

Being placental animals, humans have an embryonic cloaca which divides into separate tracts during the

congenital disorders result in persons being born with a cloaca, including persistent cloaca and sirenomelia
(mermaid syndrome).

Reptiles

In reptiles, the cloaca consists of the urodeum, proctodeum, and coprodeum.

reptile reproduction). This is where reproductive activity occurs.[22]

Cloacal respiration in animals

Further information:
Cloacal respiration

Some turtles, especially those specialized in diving, are highly reliant on cloacal respiration during dives.[23] They accomplish this by having a pair of accessory air bladders connected to the cloaca, which can absorb oxygen from the water.[24]

Sea cucumbers use cloacal respiration. The constant flow of water through it has allowed various fish, polychaete worms and even crabs to specialize to take advantage of it while living protected inside the cucumber. At night, many of these species emerge through the anus of the sea cucumber in search of food.[25]

See also

References

  1. ISBN 978-0-226-28124-7
    .
  2. ISBN 978-1-4899-4656-0
    .
  3. ^ Harris, R. L., Cameron, E. Z., Davies, N. W., & Nicol, S. C. (2016). Chemical cues, hibernation and reproduction in female short-beaked echidnas (Tachyglossus aculeatus setosus): implications for sexual conflict. In Chemical Signals in Vertebrates 13 (pp. 145-166). Springer, Cham.
  4. ^ Cassell's Latin Dictionary, Marchant, J.R.V, & Charles, Joseph F., (Eds.), Revised Edition, 1928, p.103
  5. ^ Harper, Douglas. "cloaca". Online Etymology Dictionary.
  6. Perseus Project
    .
  7. ISBN 978-1-4214-2471-2
    .
  8. ISBN 978-0-8018-8687-4
    .
  9. ISBN 978-0-7923-8336-9. Archived
    from the original on 26 March 2014. Retrieved 5 December 2012.
  10. PMID 17297135
    .
  11. doi:10.1242/jeb.02737
    .
  12. ^
    ISBN 978-0-03-910284-5
    .
  13. Libbie Henrietta Hyman
    , A laboratory manual for comparative vertebrate anatomy. 1922 (1920s)
  14. ISBN 978-0-323-15331-7
    .
  15. doi:10.1111/j.1469-7998.1892.tb06835.x
    .
  16. doi:10.1016/j.mambio.2006.10.012
    .
  17. doi:10.7287/peerj.preprints.755
  18. ISBN 978-1-42143-733-0
    .
  19. S2CID 21132866
    .
  20. ISBN 978-1-4160-6477-0
    .
  21. ISBN 978-0-521-61714-7
    .
  22. ISBN 978-1-55209-605-5
    .
  23. JSTOR 3889486
    .
  24. ^ The Straight Dope - Is it true turtles breathe through their butts?
  25. ^ Aquarium Invertebrates by Rob Toonen, Ph.D.
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