WordNet

relating to or characterized by an allantois
the vascular fetal membrane that lies below the chorion and develops from the hindgut in many embryonic higher vertebrates (reptiles, birds and mammals)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/10/17 14:59:30」(JST)

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Allantois (/əˈlæntɔɪs/; plural allantoides or allantoises) is a part of a developing amniote's conceptus (which consists of all embryonic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste.

The allantois, along with the amnion and chorion (other embryonic membranes), identify humans, and other mammals, as amniotes. Other amniotes include reptiles, dinosaurs, and birds. Of the vertebrates, only Ichthyopsidas (fish and amphibians) lack this structure.

Function

This sac-like structure is primarily involved in nutrition and excretion, and is webbed with blood vessels. The function of the allantois is to collect liquid waste from the embryo, as well as to exchange gases used by the embryo.

In reptiles, birds, and monotremes

The structure first evolved in reptiles and birds as a reservoir for nitrogenous waste, but also as a means for oxygenation of the embryo. Oxygen is absorbed by the allantois through the egg shell. The allantois functions similarly in monotremes, which are egg-laying mammals.

In most marsupials

In most marsupials, the allantois is avascular, having no blood vessels, but still serves the purpose of storing nitrogenous (NH₃) waste. Also, most marsupial allantoises do not fuse with the chorion. An exception is the allantois of the bandicoot, which has a vasculature, and fuses with the chorion.

In placental mammals (Eutheria)

In placental mammals, the allantois is part of and forms an axis for the development of the umbilical cord.

The mouse allantois consists of mesodermal tissue, which undergoes vasculogenesis to form the mature umbilical artery and vein.^[1]

The human allantois is an endodermal evagination of the developing hindgut which becomes surrounded by the mesodermal connecting stalk. The connecting stalk forms the umbilical vasculature^{[citation needed]}. The allantois becomes the urachus which connects the fetal bladder to the yolk sac. The urachus removes nitrogenous waste from the fetal bladder.^[2] The allantois is vestigial and may regress, yet the homologous blood vessels persist as the umbilical arteries and veins connecting the embryo with the placenta.^[3]

Clinical significance

During the third week of development, the allantois protrudes into the area of the urogenital sinus. Between the 5th and 7th week of development, the allantois will become the urachus, a duct between the bladder and the yolk sac. A patent allantois can result in urachal cyst.

Etymology

The word comes from the Greek words allanto-, meaning sausage, and eidos, meaning shape or similarity.

Additional images

Section through the embryo.
Diagram showing later stage of allantoic development with commencing constriction of the yolk-sac.
Diagram showing the expansion of amnion and delimitation of the umbilicus.
Model of human embryo 1.3 mm. long.
Tail end of human embryo from fifteen to eighteen days old.
Cloaca of human embryo from twenty-five to twenty-seven days old.
Tail end of human embryo twenty-five to twenty-nine days old.
Tail end of human embryo thirty-two to thirty-three days old.
Opened uterus with cat fetus in midgestation: 1 umbilicus, 2 amnion, 3 allantois, 4 Yolk sac, 5 developing marginal hematoma, 6 maternal part of placenta (endometrium)
Ultrasound of fetus showing urachus duct from bladder to the umbilicus.
Ultrasound of fetus showing urachus duct from bladder to the umbilicus.
Ultrasound of fetus showing urachus duct from bladder to the umbilicus.
Ultrasound of fetus showing urachus duct from bladder to the umbilicus.
Ultrasound of fetus showing urachus duct from bladder to the umbilicus.

References

^ Downs, K.M. 1998. "The Murine Allantois". Current Topics in Developmental Biology vol. 39, pp 1-33.
^ First AID for the USMLE Step 1 2008
^ http://www.answers.com/topic/allantois

External links

Diagram at University of Texas - Arlington

UpToDate Contents

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1. 臍帯異常の出生前診断および産科的マネージメント prenatal diagnosis and obstetrical management of umbilical cord abnormalities
2. 単一臍動脈 single umbilical artery
3. 胎盤病理組織報告 the placental pathology report

English Journal

Glycoprotein J of infectious laryngotracheitis virus is required for efficient egress of infectious virions from cells.

Mundt A, Mundt E, Hogan RJ, Garcia M.SourcePoultry Diagnostic and Research Center, University of Georgia, Athens, GA, USA.
The Journal of general virology.J Gen Virol.2011 Nov;92(Pt 11):2586-9. Epub 2011 Jul 13.
Glycoprotein J (gJ) of infectious laryngotracheitis virus (ILTV) represents a major viral antigen and is dispensable for replication in cell culture and chickens. We generated gJ deletion mutants derived from the United States Department of Agriculture standard challenge strain (USDA-ch), a GFP-expr
PMID 21752963

Identity and fate of Tbx4-expressing cells reveal developmental cell fate decisions in the allantois, limb, and external genitalia.

Naiche LA, Arora R, Kania A, Lewandoski M, Papaioannou VE.SourceCancer and Developmental Biology Lab, National Cancer Institute - Frederick, Frederick, Maryland, USA.
Developmental dynamics : an official publication of the American Association of Anatomists.Dev Dyn.2011 Oct;240(10):2290-300. doi: 10.1002/dvdy.22731.
T-box gene Tbx4 is critical for the formation of the umbilicus and the initiation of the hindlimb. Previous studies show broad expression in the allantois, hindlimb, lung and proctodeum. We have examined the expression of Tbx4 in detail and used a Tbx4-Cre line to trace the fates of Tbx4-expressing
PMID 21932311

Japanese Journal

Effects of several virucidal agents on inactivation of influenza, Newcastle disease, and avian infectious bronchitis viruses in the allantoic fluid of chicken eggs

Abe Motoharu,Kaneko Kumi,Ueda Ai [他]
Japanese Journal of Infectious Diseases 60(6), 342-346, 2007-11
NAID 40015714567

Quantitative analysis of allantoin and allantoic acid in yam tuber, mucilage, skin and bulbil of the Dioscorea species

FU Y. C.
Food Chem. 94, 541-549, 2006
NAID 30008865894

Related Pictures

★リンクテーブル★

拡張検索	「chorioallantoic」「allantoic membrane」

「chorioallantoic」

Allantois
	Diagram illustrating early formation of allantois and differentiation of body-stalk.
	Sectional plan of the gravid uterus in the third and fourth month.
Details
Latin	Aallantois
Days	16
Precursor	yolk sac
Gives rise to	Umbilical cord
Identifiers
Gray's	p.54
MeSH	A10.615.284.147
Code	TE E6.0.1.2.0.0.2
	Anatomical terminology