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The chorioallantoic membrane (CAM), also known as the chorioallantois, is a highly vascularized membrane found in the eggs of certain amniotes like birds and reptiles. It is formed by the fusion of the mesodermal layers of two extra-embryonic membranes – the chorion and the allantois. [1] It is the avian homologue of the mammalian placenta.
The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation.It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal ...
The vasculature of the body-stalk develops into umbilical arteries that carry deoxygenated blood to the placenta. [12] It is externally continuous with the proctodeum and internally continuous with the cloaca. The embryonic allantois becomes the fetal urachus, which connects the fetal bladder (developed from cloaca) to the yolk sac.
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.
Placenta can also be divided according to what kind of structure it develops from. There are two vessel-rich features in the amniote, the yolk sac and the allantois. When the chorion fuses with the former, the result is a choriovitelline placenta. When it fuses with the latter, the result is a chorioallantoic placenta.
Placenta with attached fetal membranes (ruptured at the margin at the left in the image), which consists of the chorion (outer layer) and amnion (inner layer).. The part of the chorion that is in contact with the decidua capsularis undergoes atrophy, so that by the fourth month scarcely a trace of the villi is left.
From ancient history to the modern day, the clitoris has been discredited, dismissed and deleted -- and women's pleasure has often been left out of the conversation entirely. Now, an underground art movement led by artist Sophia Wallace is emerging across the globe to challenge the lies, question the myths and rewrite the rules around sex and the female body.
In bandicoots, an additional chorioallantoic placenta forms, although it lacks the chorionic villi found in eutherian placentas. The evolution of reproduction in marsupials, and speculation about the ancestral state of mammalian reproduction , have engaged discussion since the end of the 19th century.