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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. This part of the chorion becomes smooth, [2] and is named the chorion laeve (from the Latin word levis, meaning smooth). As it takes no share in the formation of the placenta, this is also ...
The trophoblast layer differentiates into amnion and the chorion, which then comprise the fetal membranes. [4] The amnion is the innermost layer and, therefore, contacts the amniotic fluid, the fetus and the umbilical cord. [5] The internal pressure of the amniotic fluid causes the amnion to be passively attached to the chorion. [4]
The yolk sac, amnion, chorion, and allantois are the four extraembryonic membranes that lie outside of the embryo and are involved in providing nutrients and protection to the developing embryo. [5] They form from the inner cell mass; the first to form is the yolk sac followed by the amnion which grows over the developing embryo. The amnion ...
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.
The chorion and amnion membranes are labelled in this depiction of a growing fetus in the uterus. The amniotic sac consists of two parts: The outer membrane is the chorion. It is closest to the mother and physically supports the much thinner amnion. The chorion is the last and outermost of the membranes that make up the amniotic sac. [13]
The amnion, along with the chorion, the yolk sac and the allantois protect the embryo. In birds, reptiles and monotremes, the protective sac is enclosed in a shell. In marsupials and placental mammals, it is enclosed in a uterus. The amnion is a feature of the vertebrate clade Amniota, which includes reptiles, birds, and mammals.
Google Dictionary is an online dictionary service of Google that can be accessed with the "define" operator and other similar phrases [note 1] in Google Search. [2] It is also available in Google Translate and as a Google Chrome extension. The dictionary content is licensed from Oxford University Press's Oxford Languages. [3]
The word chorion was used by Galen to refer to the outer membrane enclosing the fetus. Both meanings of the word plexus are given as pleating, or braiding. [22] As often happens language changes and the use of both choroid or chorioid is both accepted. Nomina Anatomica (now Terminologia Anatomica) reflected this dual usage. [citation needed]