- Allantois
Infobox Embryology
Name = Allantois
Latin =
GraySubject = 12
GrayPage = 54
Caption = Diagram illustrating early formation of allantois and differentiation of body-stalk.
Caption2 = Sectional plan of the gravid uterus in the third and fourth month.
System =
CarnegieStage =
Days = 16
Precursor =yolk sac
GivesRiseTo =Umbilical cord
MeshName = Allantois
MeshNumber = A10.615.284.147
DorlandsPre = a_24
DorlandsSuf = 12121253Allantois (plural "allantoides" or "allantoises") is a part of a developing animal
conceptus (which consists of allembryo nic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste.The allantois, along with the
amnion andchorion (other embryonic membranes), identify humans asamniote s, along withreptile s,dinosaur s,bird s, and othermammal s.Function
This sac-like structure is primarily involved in
nutrition andexcretion , and is webbed withblood vessel s.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 andbirds as a reservoir for nitrogenous waste, but also as a means for oxygenation of the embryo.Oxygen is absorbed by the allantois through theegg shell . The allantois functions similarly inmonotremes , which are egg-layingmammals .In most marsupials
In most
marsupials , the allantois is avascular, having no blood vessels, but still serves the purpose of storing nitrogenous (N2) waste.Also, most marsupial allantoises do not fuse with the
chorion . An exception is the allantois of thebandicoot , 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 theumbilical cord .* The
mouse allantois consists ofmesoderm al tissue, which undergoes vasculogenesis to form the mature umbilical artery and vein. [Downs, K.M. 1998. "The Murine Allantois". "Current Topics in Developmental Biology" vol. 39, pp 1-33.]* The
human allantois is anendoderm al evagination of the developinghindgut which becomes surrounded by themesodermal connecting stalk. The connecting stalk forms the umbilical vasculature. These endodermal and mesodermal tissues together form the human umbilical cord. The allantois later becomes theurachus , which removes nitrogenous waste from the fetal bladder [First AID for the USMLE Step 1 2008] .Pathology
A patent allantois can result in
urachal cyst .Etymology
The word comes from the Greek word for
sausage , which the allantois resembles.
=AdditionalReferences
External links
* [http://www.uta.edu/biology/westmoreland/classnotes/1442/Chapter_47_files/image007.gifDiagram at University of Texas - Arlington]
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См. также в других словарях:
Allantois — Al*lan to*is, Allantoid Al*lan toid, ] n.. (Anat.) A membranous appendage of the embryos of mammals, birds, and reptiles, in mammals serving to connect the fetus with the parent; the urinary vesicle. [1913 Webster] … The Collaborative International Dictionary of English
Allantŏis — (gr.), Harnhaut, eine längliche, wurstförmige, dünne Blase, die während der 2 ersten Monate nach der Befruchtung bei dem aus dem Ei sich entwickelnden Fötus der Menschen u. Thiere zwischen 2 anderen Eihäuten (dem Chorion u. Amnion) in der Nähe… … Pierer's Universal-Lexikon
Allantōis — (griech., Harnhaut, Harnsack), eine der Hüllen, die den Embryo der Reptilien, Vögel und Sänger umgeben. Sie entsteht als eine Ausstülpung des Darmes, wächst in Form einer gestielten Blase aus der Bauchhöhle des Embryos hervor und bis zur innern… … Meyers Großes Konversations-Lexikon
Allantois — Allantōis (grch.), Harnhaut, eine Hülle des Embryos der höhern Wirbeltiere (Allantoidĕa: Säugetiere, Vögel, Reptilien), vermittelt bei Reptilien und Vögeln die Atmung, bei den Säugetieren durch Bildung des Mutterkuchens auch noch die … Kleines Konversations-Lexikon
Allantoïs — Allantoïs, bei dem Fötus mehrerer Säugethiere eine zarte, weiße Haut zwischen dem Chorium und Amnium, in Form einer wurstförmigen Blase, durch die Nabelschnur mittelst der Blasenschnur mit der Harnblase zusammenhängend. In ihr findet sich die… … Herders Conversations-Lexikon
Allantois — ⇒ Embryonalhüllen … Deutsch wörterbuch der biologie
allantois — [ə lan′tō is] n. pl. allantoides [al΄ən tō′ə dēz΄] [ModL < Gr allantoeidēs, sausage shaped < allas, sausage (prob. < dial. allē, garlic, via Oscan * allo < L alium, allium) + eidēs, OID] a membranous pouch with a rich blood supply in… … English World dictionary
Allantois — Eröffnete Gebärmutter einer Katze mit einem Fötus in der Mitte der Trächtigkeit. 1 Nabel, 2 Amnion, 3 Allantois, 4 Dottersack, 5 sich entwickelndes Randhämatom, 6 mütterlicher Teil der Plazenta. Allantois (gr. ho allás, allántos: „Die… … Deutsch Wikipedia
allantois — A fetal membrane developing from the hindgut (or yolk sac, in humans). In humans it is vestigial; externally, in mammals, it contributes to the formation of the umbilical cord and placenta; in birds and reptiles, it lies close beneath the porous… … Medical dictionary
allantois — /euh lan toh is, toys/, n. Embryol., Zool. a vascular, extraembryonic membrane of birds, reptiles, and certain mammals that develops as a sac or diverticulum from the ventral wall of the hindgut. [1640 50; < NL < Gk allantoeidés, wrongly taken… … Universalium
