Allantois Apr 2026

: In humans, the allantois is largely vestigial as a sac but remains vital as a structural precursor. Its blood vessels become the umbilical arteries and veins , connecting the fetus to the placenta for nutrient and gas exchange. 3. Developmental Fate in Humans

The is a critical extra-embryonic membrane found in the embryos of reptiles, birds, and mammals that primarily functions in waste storage and gas exchange . In egg-laying species, it acts as a repository for nitrogenous waste and works with the chorion to facilitate respiration, while in most mammals, it evolves to form the structure of the umbilical cord. 1. Evolutionary Significance and Structure allantois

: The allantois is typically small and unattached in most marsupials, though it does fuse with the chorion in specific groups like bandicoots and koalas. : In humans, the allantois is largely vestigial

: It is present in all amniotes, including reptiles, birds, and mammals. Developmental Fate in Humans The is a critical