Diagram illustrating a chicken egg in its 9th day with all extraembryonic membranes
Allantois and other fetal membranes shown at end of second month of human pregnancy
Details
Pronunciation
/əˈlæntɔɪs/, /əˈlæntoʊɪs/
Days
16
Identifiers
Latin
allantois
MeSH
D000482
TE
E6.0.1.2.0.0.2
Anatomical terminology
[edit on Wikidata]
The allantois (/əˈlæntoʊɪs/a-LAN-toe-iss;[1] pl.: allantoides or allantoises) is a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extraembryonic tissues). It helps the embryo exchange gases and handle liquid waste.
The allantois, along with the amnion, chorion, and yolk sac (other extraembryonic membranes), identify humans and other mammals, birds, and reptiles as amniotes. These extraembryonic membranes that form the embryo have aided amniotes in the transition from aquatic to terrestrial environments.[2] Fish and amphibians are anamniotes, and lack the allantois. In mammals the extraembryonic membranes are known as the fetal membranes.
^Jones, Daniel (October 6, 2011). Cambridge English Pronouncing Dictionary. Cambridge University Press. ISBN 9780521765756 – via Google Books.
^Chuva de Sousa Lopes, Susana M.; Roelen, Bernard A. J.; Lawson, Kirstie A.; Zwijsen, An (2022-12-05). "The development of the amnion in mice and other amniotes". Philosophical Transactions of the Royal Society B: Biological Sciences. 377 (1865): 20210258. doi:10.1098/rstb.2021.0258. ISSN 0962-8436. PMC 9574641. PMID 36252226.
cord. While the function of the allantois remains conserved, there is a divergence in the characteristics of the allantois among mammalian species. Structural...
and fetus in humans and other mammals. They are the amnion, chorion, allantois, and yolk sac. The amnion and the chorion are the chorioamniotic membranes...
connected to the yolk sac, the allantois, and via the umbilical cord, the placenta. The yolk sac, amnion, chorion, and allantois are the four extraembryonic...
increased need for oxygen. To compensate for this, the chorion and the allantois fuse together to form the chorioallantoic membrane. Together these form...
membranes (amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage), thicker and keratinized skin...
a congenital disorder caused by the partial persistence of the allantois. The allantois, which later becomes the urachus, connects an embryo's bladder...
the crystals previously isolated] are allantois acid, or the same substance that one found in the allantois fluid of cows; we will call it "allantoin"...
the allantois, and thence upon the umbilical cord; the other is the smooth outer layer, continued upon the outer or chorional surface of the allantois, and...
surrounds the yolk, the amnion which surrounds and cushions the embryo, the allantois which among avians stores embryonic waste and assists with the exchange...
The urachus is a fibrous remnant of the allantois, a canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord...
or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion is an accumulation of excessive fluid in the allantoic...
It contains the urachus, which is the obliterated form of the allantois. The allantois forms a communication between the cloaca (terminal part of hindgut)...
islands arise external to the developing embryo on the umbilical vesicle, allantois, connecting stalk and chorion. They are also known as Pander's islands...
pregnancy. The up to fist-sized hippomanes are either attached to the allantois membrane or swim freely in the allantoic fluid. Occasionally such formations...
connecting stalk) creates a tube with a covering of amniotic membrane with allantois and umbilical vessels as its content and mesoderm of the connecting stalk...
similar to that of the allantois in mammals. Its growth starts from day 3 of embryonic development. Development of the allantois occurs extra embryonically...
urachal fistula is a congenital disorder caused by the persistence of the allantois (later, urachus), the structure that connects an embryo's bladder to the...
derived from the urogenital sinus, and it is initially continuous with the allantois. In human males, the base of the bladder lies between the rectum and the...
small allantois is found in modern amphibians. Later came the amnion surrounding the fetus proper, and the chorion, encompassing the amnion, allantois, and...
cell mass will give rise to the pre-embryo, the amnion, yolk sac and allantois, while the fetal part of the placenta will form from the outer trophoblast...
A urachal cyst is a sinus remaining from the allantois during embryogenesis. It is a cyst which occurs in the remnants between the umbilicus and bladder...
covered with leathery or calcareous shells. An amnion (5), chorion (6), and allantois (8) are present during embryonic life. The eggshell (1) protects the crocodile...
derives from the urogenital sinus, and it is initially continuous with the allantois. The upper and lower parts of the bladder develop separately and join...
provides the embryo with protection against shock from movement The allantois helps the embryo obtain oxygen and handles metabolic waste The chorion...
causes an indirect inguinal hernia. Germ cells migrate from near the allantois and colonize the primordial gonads. In the female, the germ cells colonise...
The vesico-urethral portion is the deepest portion, continuous with the allantois. It absorbs the ends of the mesonephric ducts and the associated ends...
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