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The fetal membranes are the four extraembryonic membranes, associated with the developing embryo, and fetus in humans and other mammals. They are the amnion, chorion, allantois, and yolk sac. [1] The amnion and the chorion are the chorioamniotic membranes that make up the amniotic sac which surrounds and protects the embryo. [2]
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 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 .
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 pia mater (Latin: tender mother) [9] is a very delicate membrane. It is the meningeal envelope that firmly adheres to the surfaces of the brain and spinal cord, following all of the brain's contours (gyri and sulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be ...
Scientists just discovered a secret fourth membrane in the human brain. Here's why that matters.
That’s because the brain is surrounded by a semipermeable membrane called the blood-brain barrier. Research on microplastics in the body is still new, and whether these microscopic bits of ...
The chorionic villi are at first small and non-vascular. 13–15 days: trophoblast only [1] Secondary: The villi increase in size and ramify, while the mesoderm grows into them. 16–21 days: trophoblast and mesoderm [1] Tertiary: Branches of the umbilical artery and umbilical vein grow into the mesoderm, and in this way the chorionic villi are ...