A membranous appendage of the embryos of mammals, birds, and reptiles, -- in mammals serving to connect the fetus with the parent; the urinary vesicle.
a small, vascularized membrane between the chorion and amnion of the fetus; serves as an early site for blood formation
An extraembryonic membrane of reptiles, birds, and mammals. Saclike outgrowth of tissue that extends outward from the gut of a developing embryo. In mammalian embryos it is situated between the chorion and amnion and functions in respiration, excretion, and nutrition.
An organ in the embryo of birds which develops into part of the umbilical cord and unites with the chorion, forming the placenta. This membrane supplies oxygen to the embryo and stores waste material.
A membranous sac that grows from the lower gut and it combines with the chorion to form the umbilical cord and placenta.
extraembryonic membrane, generates vascularization of chorion, proximally forms urinary bladder.
Sac that develops between the eggshell and amnion for respiration of the embryo in a cleidoic egg.
vascular fetal membrane that develops from the hindgut in embryonic higher vertebrates (reptiles, birds and mammals)
One of four extraembryonic membranes; serves as a repository for the embryo's nitrogenous waste.
A sac connected to the emrbyo's abdomen making respiration by the embryo possible; it also stores excretions, absorbs albumen used for food by the embryo, and absorbs calcium from the egg shell for the structural needs of the embryo.
A sac-like organ of an embryo that obtains oxygen, nourishment, and calcium from the egg and in which is deposited the embryo's waste products.
Gr. allantos - a sausage]. An extraembryonic membrane formed by an extension of the hindgut into the extraembryonic coelom and consisting of endoderm and splanchnic mesoderm. In birds and reptiles, it fuses with the chorion to form the chorioallantoic membrane which assists in respiration, and in addition it is the site of storage of nitrogenous wastes. In eutherian mammals, it forms the vessels of the umbilical cord and fuses with the chorion to form the embryonic portion of the placenta.
One of the four extraembryonic membranes; provides vascularity to the chorion and is therefore essential to placenta formation; the proximal portion becomes the urinary bladder.
The allantois is a membranous sac, which becomes highly vascular, extends outside the embryo, and becomes involved in nutrient and oxygen absorption. It fuses with the chorion to form part of the placenta, the chorioallantois. It is an outgrowth of the hind gut composed of endoderm overlain by mesoderm.
Allantois (plural allantoides or allantoises) is a part of a developing animal conceptus (which consists of all embryonic and extra-embryonic tissues).