What is the function of Extraembryonic membrane allantois?
The third membrane is the allantois, which forms as a small pouch at the posterior (tail) end of the embryo. Although it has important functions in waste storage and gas exchange in birds and reptiles, the human allantois is a vestigial sac not used for these functions.
What does the allantois become?
Function of Allantois Somewhere between the fifth and seventh weeks of embryonic development, the allantois becomes a fibrous cord that is referred to as the urachus, the function of which is to drain the fetus’s urinary bladder.
What is the allantois membrane?
allantois, an extra-embryonic membrane of reptiles, birds, and mammals arising as a pouch, or sac, from the hindgut. In reptiles and birds it expands greatly between two other membranes, the amnion and chorion, to serve as a temporary respiratory organ while its cavity stores fetal excretions.
What is allantois in human embryo?
The allantois arises as an endodermally lined ventral outpocketing of the hindgut (see Figure 1). In the human embryo, it is just a vestige of the large, saclike structure that is used by the embryos of many mammals, birds, and reptiles as a major respiratory organ and repository for urinary wastes.
What is the function of the allantois in an embryo?
It helps the embryo exchange gases and handle liquid waste. The allantois, along with the amnion and chorion (other extraembryonic membranes ), identify humans and other mammals as well as reptiles (including birds) as amniotes. Of the vertebrates, only the anamniotes ( amphibians and non- tetrapod fish) lack this structure.
Where is the allantois membrane located?
Allantois Definition The allantois is one of the four main membranes that surround an embryo. It is found near the posterior of the embryo, since that’s where its development begins.
What vertebrates have the allantois?
The allantois, along with the amnion and chorion (other extraembryonic membranes), identify humans and other mammals as well as reptiles (including birds) as amniotes. Of the vertebrates, only the anamniotes (amphibians and non-tetrapod fish) lack this structure.
What is the structure of the extraembryonic membrane?
The extraembryonic membranes consist of the chorion (the combination of trophoblast plus underlying extraembryonic mesoderm), amnion, yolk sac, and allantois.