The allantois (/ ə ˈ l æ n t oʊ ɪ s / a-LAN-toe-iss; [1] pl.: allantoides or allantoises) is one the extraembryonic membranes arising from the yolk sac. It is a hollow sac-like structure filled with clear fluid that forms part of the developing conceptus in an amniote that helps the embryo exchange gases and handle liquid waste.

2017年4月28日 · The allantois is characteristic of reptiles, birds, and mammals, and lies between two other extraembryonic membranes: the amnion, the innermost layer, which covers and protects the embryo; and the chorion, which is the outermost layer, housing the embryo and all the other extraembryonic membranes.

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 …

allantois An extraembryonic membranous sac found in a developing animal conceptus, which is comprised of all embryonic and extraembryonic tissues. It is intimately involved in gas and liquid waste exchange, as well as erythropoiesis; it gives rise to the foetal umbilical arteries and vein and contributes to the formation of the urinary bladder.

The meaning of ALLANTOIS is a vascular fetal membrane of reptiles, birds, and mammals that is formed as a pouch from the hindgut and that in placental mammals is intimately associated with the chorion in formation of the placenta.

2025年1月14日 · The allantois is an essential embryonic structure in the development of amniotes, including reptiles, birds, and mammals. It plays a role in waste management, gas exchange, and the formation of important anatomical structures. Understanding the allantois provides insight into evolutionary biology and developmental processes across different ...

2024年6月16日 · Structure and Composition of the Allantois. The allantois, a vital structure in embryonic development, is composed of an inner endodermal layer and an outer mesodermal layer. This sac-like structure forms as an outpouching of the hindgut in vertebrate embryos.

2024年5月10日 · Allantois is a tube-like structure of the yolk sac that helps to remove the nitrogenous waste materials from the embryo. It is the mid-layer of the placenta and the blood vessels that originate from the umbilicus traverse.

The allantois is responsible for the induction of placental development and is the site of extraembryonic vasculogenesis, which occurs independently in the mesodermal wall of the allantois and contributes to the formation of the umbilical vessels.

2007年5月1日 · The allantois, precursor tissue of the mature umbilical cord, is a universal feature of all placental mammals that establishes the vital vascular bridge between the fetus and its mother. The allantois differentiates into the umbilical blood vessels, which become secured onto the chorionic component of the placenta at one end and onto the fetus ...