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During growth and development of the embryo, there is an increased need for oxygen. To compensate for this, the chorion and the allantois fuse together to form the chorioallantoic membrane. Together these form a double membrane, which functions to remove carbon dioxide and to replenish oxygen through the porous shell.
The chorionic membrane is a fibrous tissue layer containing the fetal blood vessels. [4] Chorionic villi form on the outer surface of the chorion, which maximise surface area for contact with maternal blood. [4] The chorionic villi are involved in fetal-maternal exchange. [10]
In developmental biology, choriogenesis is the formation of the chorion, an outer membrane of the placenta that eventually forms chorionic villi that allow the transfer of blood and nutrients from mother to fetus. [1]
The tela choroidea (or tela chorioidea) is a region of meningeal pia mater that adheres to the underlying ependyma, and gives rise to the choroid plexus in each of the brain’s four ventricles. [ 1 ] [ 2 ] Tela is Latin for woven and is used to describe a web-like membrane or layer. [ 3 ]
The amniotic sac, also called the bag of waters [1] [2] or the membranes, [3] is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes that hold a developing embryo (and later fetus) until shortly before birth .
Scientists just discovered a secret fourth membrane in the human brain. Here's why that matters.
For a number of substances, the BCSFB is the primary site of entry into brain tissue. [14] The blood–cerebrospinal fluid barrier has also been shown to modulate the entry of leukocytes from the blood to the central nervous system. The choroid plexus cells secrete cytokines that recruit monocyte-derived macrophages, among other cells, to the ...
Next, another layer called the exocoelomic membrane or Heuser's membrane will appear and surround the cytotrophoblast, as well as the primitive yolk sac. [11] The syncytiotrophoblast will grow and will enter a phase called lacunar stage, in which some vacuoles will appear and be filled by blood in the following days.