fetal membrane

n. Any of the membranous structures closely associated with or surrounding a developing vertebrate embryo, including the amnion, chorion, allantois, and yolk sac. Also called embryonic membrane.

Thesaurus

Noun

fetal membrane - any membrane that functions for the protection or nourishment or respiration or excretion of a developing fetusamnion, amnios, amniotic sac - thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)chorion - the outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals)allantois - the vascular fetal membrane that lies below the chorion and develops from the hindgut in many embryonic higher vertebrates (reptiles, birds and mammals)embryonic membrane, caul, veil - the inner membrane of embryos in higher vertebrates (especially when covering the head at birth)tissue layer, membrane - a pliable sheet of tissue that covers or lines or connects the organs or cells of animals or plantsumbilical, umbilical cord - membranous duct connecting the fetus with the placenta

fetal membrane

Fetal membrane

One of the membranous structures which surround the embryo during its developmental period. Since such membranes are external to the embryo proper, they are called extraembryonic membranes. They function in the embryo's protection, nutrition, respiration, and excretion.

There are four fetal membranes—the amnion, chorion, yolk sac, and allantois. In the course of development, the chorion becomes the outermost, and the amnion the innermost, membrane surrounding the developing embryo. As the allantois increases in size, it expands and becomes closely associated, if not fused, with the chorion. The two membranes together are known as the chorioallantoic membrane.

The amniotic cavity within which the embryo is enclosed becomes filled with an aqueous fluid which gives osmotic and physical protection to the embryo during the remainder of its fetal existence. Smooth muscle fibers in the amnion spontaneously contract and gently rock the embryo before it develops the capacity for spontaneous movement.

As the stored nutrients of the yolk are depleted during development, the yolk sac gradually decreases in size and is eventually incorporated into the midgut of the embryo. The yolk sac in the nonyolky eggs of placental mammals is vestigial. It has evolutionary but essentially no functional significance.

At the time of birth or hatching, the embryo becomes completely separated from the amnion and chorion and from the major portion of the allantois. The proximal portion of the latter remains within the embryo, however, as the urinary bladder. See Allantois, Amnion, Chorion, Yolk sac

fetal membrane

[′fēd·əl ′mem‚brān] (embryology) Any one of the membranous structures which surround the embryo during its development period. Also known as extraembryonic membrane.

fetal membrane

Related to fetal membrane: fetal membrane slip

noun

Words related to fetal membrane

noun any membrane that functions for the protection or nourishment or respiration or excretion of a developing fetus

Related Words

amnion
amnios
amniotic sac
chorion
allantois
embryonic membrane
caul
veil
tissue layer
membrane
umbilical
umbilical cord