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 ?
The amnion is comprised of cells that have strikingly similar characteristics to their stem cell counterparts, including the ability to express two key genes that give embryonic stem cells their unique capability for developing into any kind of specialized cell, said researchers at the University of Pittsburgh.
Human amnion as temporary biological wound dressing has remained beneficial and cost-effective means of treating burns in developing countries.
The chorionic sac is sometimes called the gestational sac, but the latter term applies only to pregnancies after the amnion fuses with the chorion later in the first trimester, Dr.
2] of amnion must be extracted in order to acquire an adequate amount of DNA.
For accurate results the fetus should be in a neutral position, away from the amnion, and seen in sagittal section, Dr.
Steroids, corticotropin-releasing hormone, ACTH and prostaglandin interactions in the amnion and placenta of early pregnancy in man.
In previously published scientific studies, MiMedx dehydrated human amnion/chorion membrane (dHACM), comprised of gently cleansed, laminated amnion and chorion membranes, has been shown to stimulate cellular proliferation and migration responses in a variety of adult stem cells from normal donors, including bone marrow mesenchymal stem cells (BM-MSCs), adipose derived stem cells (ADSCs), and hematopoetic stem cells (HSCs).
Meconium changes were separated into 4 groups: pigment in the amnion only, pigment in the amnion and decidua, a green-stained umbilical cord, and meconium-associated vascular necrosis of large fetal vessels.
His in vitro study, which earned the meeting's Best Abstract award, involved culturing human amnion cells from the placentas of six women undergoing term elective C-section.
Identification of HbA as the predominant hemoglobin species in the specimen indicates that the blood source is of maternal origin, likely as the result of ingestion of blood in the amnion or at birth.
Live fetuses in one gestational sac are monochorionic; in these cases, check to see whether each twin has a separate amnion or whether one amnion surrounds both together.
At that point in monochorionic-diamniotic pregnancies, the amnion is a thin sonolucent line within the chorion.