WordNet

(zoology) the cavity (in birds, reptiles, amphibians, most fish, and monotremes but not mammals) at the end of the digestive tract into which the intestinal, genital, and urinary tracts open

PrepTutorEJDIC

(鳥類,爬(は)虫類,両生類などの) 排出腔｛はいしゅつくう｝、下水道｛げすいどう｝

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/10/04 08:42:34」(JST)

wiki en

[Wiki en表示]

An avian cloaca or vent; in this example, a Red-tailed hawk (Buteo jamaicensis)

Cloacal opening in an Australian brushtail possum

In zoological anatomy, a cloaca /kloʊˈeɪkə/ is the posterior orifice that serves as the only opening for the intestinal, reproductive, and urinary tracts of certain animal species, opening at the vent. All amphibians, birds, reptiles, and a few mammals (monotremes, tenrecs, golden moles, and marsupial moles) possess this orifice, from which they excrete both urine and feces; this is in contrast to most placental mammals, which possess two or three separate orifices for evacuation. Excretory systems with analogous purpose in certain invertebrates are also sometimes referred to as "cloacae".

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, amphibians, and monotremes.

Etymology

The word comes from Latin, and means sewer derived from cluō, which meant "cleanse".

Birds

Birds reproduce using their cloaca; this occurs during a cloacal kiss in most birds. Birds that mate using this method touch their cloacae together, in some species for only a few seconds, sufficient time for sperm to be transferred from the male to the female.^[1] The reproductive system must be re-engorged prior to the mating season of each species. Such regeneration usually takes about a month. Birds generally produce one batch of eggs per year, but they will produce another if the first is taken away. For some birds, such as ostriches, cassowaries, kiwi, geese, and some species of swans and ducks, the males do not use the cloaca for reproduction, but have a phallus. In those, the penis helps ensure water does not wash away the male's sperm during copulation.^{[citation needed]}

One study^[2] has looked into birds that use their cloaca for cooling (see urohydrosis).^[3]

Fish

Among fish, a true cloaca is present only in elasmobranchs (sharks and rays) and lobe-finned fishes. In lampreys and in some 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.^[4]

Mammals

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

Monotremes

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

Marsupials

In marsupials (and a few birds), the genital tract is separate from the anus, but a trace of the original cloaca does remain externally.^[4] This is one of the features of marsupials (and monotremes) that suggest their basal nature, as the amniotes from which mammals evolved possessed a cloaca, and the earliest animals to diverge into the mammalian class would most likely have had this feature, too.

Unlike other marsupials, marsupial moles have a true cloaca,^[5] a fact that has been argued against a marsupial identity for these mammals.^[6]^[7]

Placentals

Most adult placental mammals have no remaining trace of the cloaca. In the embryo, the embryonic cloaca divides into a posterior region that becomes part of the anus, and an anterior region that has different fates depending on the sex of the individual: in females, it develops into the vestibule that receives the urethra and vagina, while in males it forms the entirety of the penile urethra.^[4] However, the tenrecs and golden moles, small placental mammals native to Africa, retain a cloaca as adults.

Being placental animals, humans only have an embryonic cloaca, which is split up into separate tracts during the development of the urinary and reproductive organs. However, a few human congenital disorders result in persons being born with a cloaca, including persistent cloaca and sirenomelia (mermaid syndrome).

Reptiles

Some species have modified cloacae for increased gas exchange (see Reptile respiration). This is where reproductive activity occurs.

Cloacal respiration in animals

Some aquatic turtle species can breathe underwater using a process known as cloacal respiration. In this process the turtle pump water in to their cloacal orifice (labeled 1) by contracting muscles in their inguinal pocket. The water then travels to the cloacal bursae (labeled 2) which are a pair of internal pouch-like structures. The cloacal bursae are lined with long fimbriae (labeled 3) which is the site of gas exchange.

Some turtles, especially those specialized in diving, are highly reliant on cloacal respiration during dives.^[8] They accomplish this by having a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water.^[9] Various fish, as well as polychaete worms and even crabs, are specialized to take advantage of the constant flow of water through the cloacal respiratory tree of sea cucumbers while simultaneously gaining the protection of living within the sea cucumber itself. At night, many of these species emerge from the anus of the sea cucumber in search of food.^[10]

References

^ Lynch, Wayne (2007). "The Cloacal Kiss". Owls of the United States and Canada. JHU Press. p. 151. ISBN 0-8018-8687-2.
^ Hoffman, Ty C. M.; Walsberg, Glenn E.; DeNardo, Dale F. (2007). "Cloacal evaporation: an important and previously undescribed mechanism for avian thermoregulation". The Journal of Experimental Biology 210 (5): 741–9. doi:10.1242/jeb.02705. PMID 17297135.
^ Hager, Yfke (2007). "Cloacal Cooling". The Journal of Experimental Biology 210 (5): i. doi:10.1242/jeb.02737.
^ ^a ^b ^c Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 396–399. ISBN 0-03-910284-X.
^ Gadow, H. On the systematic position of Notoryctes typhlops. Proc. Zool. Soc. London 1892, 361–370 (1892).
^ Riedelsheimer, B., Unterberger, P., Künzle, H. and U. Welsch. 2007. Histological study of the cloacal region and associated structures in the hedgehog tenrec Echinops telfairi. Mammalian Biology 72(6): 330-341.
^ On Dryolestid affinities [1]^{[full citation needed]}
^ Dunson, William A. (1960). "Aquatic Respiration in Trionyx spinifer asper". Herpetologica (Herpetologists' League) 16 (4): 277–83. JSTOR 3889486.
^ The Straight Dope - Is it true turtles breathe through their butts?
^ Aquarium Invertebrates by Rob Toonen, Ph.D.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 胎児腹壁破裂および総排泄腔外反症 body stalk anomaly and cloacal exstrophy
2. 消化管閉鎖症および閉塞の出生前診断 prenatal diagnosis of gastrointestinal atresia and obstruction

English Journal

Partial purification and characterization of a novel histidine decarboxylase from Enterobacter aerogenes DL-1.

Zou Y1, Hu W, Jiang A, Tian M.
Preparative biochemistry & biotechnology.Prep Biochem Biotechnol.2015 Aug 18;45(6):605-15. doi: 10.1080/10826068.2014.940541.
Histidine decarboxylase (HDC) from Enterobacter aerogenes DL-1 was purified in a three-step procedure involving ammonium sulfate precipitation, Sephadex G-100, and DEAE-Sepharose column chromatography. The partially purified enzyme showed a single protein band of 52.4 kD on sodium dodecyl sulfate po
PMID 25036745

Fast and continuous microorganism detection using aptamer-conjugated fluorescent nanoparticles on an optofluidic platform.

Chung J1, Kang JS1, Jurng JS1, Jung JH2, Kim BC3.
Biosensors & bioelectronics.Biosens Bioelectron.2015 May 15;67:303-8. doi: 10.1016/j.bios.2014.08.039. Epub 2014 Aug 23.
Fast and accurate pathogen detection in aquatic environments is challenging in many biomedical studies and microbial diagnostic applications. In this study, we developed a real-time, continuous, and non-destructive single cell detection method using target specific aptamer-conjugated fluorescent nan
PMID 25190089

Dynamics and diversity of microbial community succession in traditional fermentation of Shanxi aged vinegar.

Nie Z1, Zheng Y1, Du H1, Xie S1, Wang M2.
Food microbiology.Food Microbiol.2015 May;47:62-8. doi: 10.1016/j.fm.2014.11.006. Epub 2014 Nov 18.
The traditional fermentation of Shanxi aged vinegar (SAV), a well-known traditional Chinese vinegar, generally involves the preparation of starter daqu, starch saccharification, alcoholic fermentation (AF) and acetic acid fermentation (AAF). Dynamics and diversity of microbial community succession i
PMID 25583338

Physicochemical and microbiological characterization of chicha, a rice-based fermented beverage produced by Umutina Brazilian Amerindians.

Puerari C1, Magalhães-Guedes KT2, Schwan RF3.
Food microbiology.Food Microbiol.2015 Apr;46:210-7. doi: 10.1016/j.fm.2014.08.009. Epub 2014 Aug 27.
Chicha is a traditional, fermented rice beverage produced by the indigenous Umutina people in Brazil. Culture-dependent and independent approaches were used to investigate the microbial community dynamic. The bacterial population ranged from 0.1 to 6.83 log mL(-1). Lactic acid bacteria (LAB) and Bac
PMID 25475287

Japanese Journal

The Skt gene, required for anorectal development, is a candidate for a molecular marker of the cloacal plate

Hiroko Suda,Kwang-Jong Lee,Kei Semba,Fumie Kyushima,Takashi Ando,Masatake Araki,Kimi Araki,Yukihiro Inomata,Ken-ichi Yamamura,スダヒロコ,センバケイ,キュウシマフミエ,アンドウタカシ,アラキマサタケ,アラキキミ,イノマタユキヒロ,ヤマムラケンイチ,須田博子,仙波圭,久嶋史枝,安藤卓,荒木正健,荒木喜美,猪股裕紀洋,山村研一
Pediatric Surgery International 27(3), 269-273, 2011-03
… Our aims in this study are determining the Skt expression around the cloaca during the anorectal development and demonstrating the role of Skt gene in ARMs. …
NAID 120004058202

嚢胞形成を伴った肛門管重複症の1例

小角卓也,米倉竹夫,黒田征加,山内勝治,井原欣幸,太田善夫
日本小児外科学会雑誌 47(1), 85-89, 2011-02-20
症例は6か月女児.便秘と肛門の6時方向に小さな痩孔を指摘され当院に紹介された.肛門の位置は正常で肛門直腸狭窄はなく,直腸診にて直腸背側に1.5cm大の柔らかい球形の腫瘤を触知した.瘻孔は歯状線より肛門側の皺に隠れるように開口していた.瘻孔造影では,瘻孔は非常に細く直腸後壁に接し,頭側に造影剤のたまりを認めた.MRI検査では,肛門背側から仙骨前面に造影剤と一致する1.2cm大の球形の嚢胞性病変を認め …
NAID 110008506463

患者のQOLに与える影響を考慮した新たな排便機能評価試案の検討-第1報-

上野滋,森川康英,岩井潤,奥山直樹,越永従道,鈴木則夫,高松英夫,田口智章,渕本康史,松藤凡,八木誠
日本小児外科学会雑誌 47(1), 35-46, 2011-02-20
… は,QOLに影響する排便状態や必要な治療に関して重み付するほうが状態をより正確で妥当に推論できると考えられることから,この問題点を解決するため,新たな機能評価案を作成し検討した.【方法】患者97例(Cloaca8,高位型34,中間位型18,低位型37例)および専門医38名を対象とし,排便状況および排便管理がQOLに与える影響をFacial Rating Scale(FRS)で表現した15の質問調査を行った.回答に基づき,失禁,便秘,汚染,便意,排便管理の5領 …
NAID 110008506455