amnion


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Related to amnion: yolk sac, amnion nodosum

amnion

 [am´ne-on]
the innermost fetal membrane, which forms a sac filled with amniotic fluid that surrounds the embryo and later the fetus; as it enlarges it gradually obliterates the chorionic cavity and enfolds the umbilical cord. Called also bag of waters.
 Amnion, chorion, and other embryonic membranes surrounding the embryo of a placental mammal. From Dorland's, 2000.
amnion nodo´sum a nodular condition of the fetal surface of the amnion, usually appearing near the insertion of the cord; it may be associated with multiple congenital abnormalities, especially hypoplastic kidneys and oligohydramnios.

am·ni·on

(am'nē-on),
Innermost of the extraembryonic membranes enveloping the embryo in utero and containing the amniotic fluid; it consists of an internal embryonic layer with its ectodermal component and an external somatic mesodermal component; in the later stages of pregnancy the amnion expands to come in contact with and partially fuse to the inner wall of the chorionic sac; derived from the trophoblast cells.
Synonym(s): amnionic sac
[G. the membrane around the fetus, fr. amnios, lamb]

amnion

/am·ni·on/ (am´ne-on) bag of waters; the extraembryonic membrane of birds, reptiles, and mammals, which lines the chorion and contains the fetus and the amniotic fluid.amnion´ic
Enlarge picture
Amnion, chorion, and other embryonic membranes surrounding the embryo of a placental mammal.
amniot´ic
amnion nodo´sum  a nodular condition of the fetal surface of the amnion, observed in oligohydramnios associated with absence of the kidneys of the fetus.

amnion

(ăm′nē-ən, -ŏn′)
n. pl. am·nions or am·nia (-nē-ə)
A thin, tough, membranous sac that encloses the embryo or fetus of a mammal, bird, or reptile. It is filled with a serous fluid in which the embryo or fetus is suspended.

am′ni·ot′ic (-ŏt′ĭk), am′ni·on′ic (-ŏn′ĭk) adj.

amnion

[am′nē·on]
Etymology: Gk, amnos, lamb's caul
a membrane, continuous with and covering the fetal side of the placenta, that forms the outer surface of the umbilical cord. Compare chorion. amniotic, adj.

am·ni·on

(am'nē-on)
Innermost of the extraembryonic membranes enveloping the embryo and later the fetus, containing the amnionic fluid; it consists of an internal embryonic layer with its ectodermal component, and an external somatic mesodermal component; in the later stages of pregnancy, the amnion expands and partially fuses to the inner wall of the chorionic sac; derived from the trophoblast cells.
Synonym(s): amnionic sac.
[G. the membrane around the fetus, fr. amnios, lamb]

amnion

One layer of the fluid-filled double membrane surrounding the fetus before birth. The amnion is the inner of two membranes, the other being the chorion. The membranes normally rupture and release the AMNIOTIC FLUID (‘breaking of the waters’ before the baby is born.
Amnionclick for a larger image
Fig. 30 Amnion . A vertebrate embryo lying within the amnion.

amnion

an embryonic, fluid-filled sac which occurs in reptiles, birds and mammals (AMNIOTES). Formed from ECTODERM and MESODERM and containing a coelomic space (see COELOM), the amnion grows around the embryo and eventually roofs over and completely encloses it. It provides the fluid-filled space necessary for the development of the embryo of a land animal, and it also acts as a protective cushion.

amnion (amˑ·nē·n),

n membrane covering the placenta on the side that faces the fetus; also forms the outer layer of the umbilical cord.

amnion

the innermost membrane enclosing the developing fetus and which is filled with amniotic fluid; characteristic of reptiles, birds and mammals. See also amniotic.

amnion nodosum
a nodular condition of the fetal surface of the amnion, observed in oligohydramnios associated with absence of the kidneys in the fetus.

Patient discussion about amnion

Q. what does it mean when an ultrasound shows an empty amniotic sac and no baby?

A. This exact thing happened with my friend who is now 22 weeks with her first baby. She had 2 additional sacs - both empty - and the doctor said that the pregnancy had probably started out as triplets but that only one of the embryos had actually established and continued to grow.

Her doctor said it is very common for a woman to have more than one egg fertilize but that in most cases the pregnancy continues as a singleton only. She told my friend that the empty sacs would just disappear through time (which they did) and that they posed no danger to her baby.

More discussions about amnion
References in periodicals archive ?
Acute inflammation extending beyond the chorion laeve layer into the amnion, indicating acute chorioamnionitis (hematoxylin-eosin, original magnification X10).
Keeping in mind the adhesive properties of the amnion, the membrane was not sutured.
Amnion that covers chorionic plate has single row, prismatic epithelium, with a light foamy cytoplasm and large hyperchromatic nuclei.
Amnion injection stimulates tissue remodeling by modulation of tissue colony aggregates that resembles the genesis of embryonic tissue cell lines in the fetus.
Amnion zarinin proteaz inhibitoru etkisi tavsan alkali yanik modelinde gosterilmistir.
Amniotic epithelial and stromal cells are the major cell types of the amnion layer.
The basic error is the formation of an accessory neuro-enteric canal between the yolk sac and amnion, which is subsequently invested with mesenchyme to form an endomesenchymal tract that splits the notochord and neural plate.
Deri gecirgenliginin arastirildigi bu calismada sodyum izotopu ile isaretli amnion sivisina fetusun belirli sirt bolgesi batirilarak kandaki isaretli isodyum seviyelerinin zamana bagli degisiklikleri incelenmektedir.
1 Reptiles, birds, and mammals are vertebrates whose embryos develop in an amnion and are functionally and structurally supported by other extra-embryonic membranes.
O amnion e a gelatina de Wharton protegem tres importantes vasos sanguineos, essenciais para o desenvolvimento do feto: um grande vaso sanguineo que supre o desenvolvimento fetal com sangue placentario, rico em nutrientes e oxigenio e dois vasos menores, que retornam o sangue fetal, com dioxido de carbono, residuos e outras toxinas (19).
202-203|, it was stated that the exhibition "Uu higarfuera dc la historia" (A Place out of History) at rhe Museo Tamayo in Mexico City was curated by Magali Arriola, when in fact Arriola collaborated with Magnolia de la Garza on the amnion of the show.