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Related to allantois: yolk sac, urachus, Vitelline duct
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  • noun

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the vascular fetal membrane that lies below the chorion and develops from the hindgut in many embryonic higher vertebrates (reptiles, birds and mammals)

Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
Urachus is a tubular structure that connects the urinary bladder to the allantois during embryonic development.
Determination of proteinases inhibitors in lungs homogenates, blood serum, and allantois liquid was done by casein's method offered by A.
There was a marked shrinking of the walls (tunics) of the umbilical arteries and vein, and only the stalk of the allantois was prominent at this stage.
During normal development on day 20 of incubation pipping begins embryo breaks into air cell and breathing begins; allantois ceases to function and starts to dry up and embryo hatches on day 21 of incubation.
For infection, fertilized chicken eggs at embryonation day 11 were inoculated with virus into the allantois sack or onto the chorioallantoic membrane.
Death in the second half of gestation is common, with the occurrence of hydroallantois, excess accumulation of fluid in the allantois. (44)
After testing several injection sites external to the embryo (amnion layer, allantois, albumen, and yolk sac), we discovered that injecting the amnion layer at embryonic day 12 (E12) gave us the best outcome, in which the survival rate was higher than direct injections into the embryos (Table 1), as well as successful induction of hyperglycemia by E18 (Figure 1(a)).
Thereafter, the extraembryonic ectoderm develops to form the chorionic epithelium, which will be further fused with the allantois. Soon after, the chorionic trophoblast and its associated fetal blood vessels undergo extensive villous branching to create a functional mature placenta [140, 141].
In early fetal development, the ventral cloaca (the precursor of the fetal bladder) is connected to the allantois via the urachus.
In the normal embryologic development of the urogenital system, the cranial part of the urogenital sinus is continuous with the allantois, developing into the bladder and pelvic urethra; the bladder dome, posterior walls and part of lateral walls, normally arise from surrounding urogenital sinus mesenchyme.[sup.16] In recent investigation of embryonic development of bladder, Shapiro and colleagues described that bladder morphogenesis is regulated by complex epithelial-mesenchymal signalling events.[sup.17] Failure of these signalling events to occur at specified times result in bladder anomalies.
Key words or phrases include chorion, allantois, yolk sac, amnion, placenta, and umbilical cord."...
Derived from the fetal allantois, it provides a rich source of multipotent stem cells, including [CD34.sup.+] and [CD38.sup.-] haematopoietic progenitor cells.
The allantois is an endermal diverticulum that communicates with the cloaca (hind-gut).