amnion

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amnion

the innermost of two membranes (see also chorion) enclosing an embryonic reptile, bird, or mammal

Amnion

A thin, cellular, extraembryonic membrane forming a closed sac surrounding the embryo in all reptiles, birds, and mammals. It is present only in these forms; the collective term amniotes is applied to these animals. The amnion contains a serous fluid in which the embryo is immersed. See Amniota

Typically, the amnion wall is a tough, transparent, nerve-free, and nonvascular membrane consisting of two layers of cells: an inner, single-cell-thick layer of ectodermal epithelium and an outer covering of mesodermal, connective, and specialized smooth muscular tissue. Early after the formation of the amnion, waves of contraction of the muscles pass over the amniotic sac and produce a characteristic rocking of the embryo. See Germ layers

The major function of the amnion and its fluid is to protect the delicate embryo. Thus, developmental stages of terrestrial animals are provided with the same type of cushioning against mechanical shock as is provided by the water environment of aquatic forms. See Fetal membrane

Amnion

 

one of the embryonic membranes found in a number of vertebrates (reptiles, birds, mammals) and invertebrates. Depending on whether the amnion is present or absent, two groups are distinguished—the Amniota (or higher) and the Anamnia (or lower). The amnion develops around the embryo in the form of folds of the extraembryonic ectoderm and the peritoneum parietal of the lateral plates of the mesoderm—that is, the external and median germ layers. After accretion of the edges of the folds, the embryo is within two membranes—the inner membranes, or amnion, and the external, or serous, membrane (called the chorion in mammals). In reptiles the amnion is without vessels; in birds and mammals it develops vessels and contractile muscular elements. The amniotic cavity becomes filled with a large amount of exudate from the vessels—the so-called amniotic, or fetal, fluid which protects the embryo from mechanical injury and desiccation. The fluid contains organic compounds (proteins, urea, sugar, hormones) and also inorganic salts. The amnion bursts during parturition and the amniotic fluid escapes; the remnants of the amnion on the body of the newborn individual are called the rubashechka (“little shirt”). The blastoderm in insects, scorpions, nemerteans, and sea urchins is also called the amnion.

amnion

[′am·nē‚än]
(embryology)
A thin extraembryonic membrane forming a closed sac around the embryo in birds, reptiles, and mammals.
References in periodicals archive ?
Furthermore, placental amnion could be supplied with different amounts of oxygen and different patterns of nutrients than reflected amnion.
Kawai et al., "In vitro production of prostaglandins E, F, and 6-keto prostaglandin F1 alpha by human pregnant uterus, decidua and amnion," Prostaglandins and Medicine, vol.
Vertua et al., "Engraftment potential of human amnion and chorion cells derived from term placenta," Transplantation, vol.
Parolini, "Human amnion mesenchyme harbors cells with allogeneic T-cell suppression and stimulation capabilities," Stem Cells, vol.
Vertua et al., "Amniotic mesenchymal tissue cells inhibit dendritic cell differentiation of peripheral blood and amnion resident monocytes," Cell Transplantation, vol.
Peterbauer et al., "Human mesenchymal stem cells from adipose tissue and amnion influence T-cells depending on stimulation method and presence of other immune cells," Stem Cells and Development, vol.
We investigated the methylation status of OXTR, given its significant role in parturition [17] and its labor-associated expression paThern in the amnion [18], which makes it a potential candidate gene for PTB.
Bisulfite-converted DNA extracted from amnion tissues (TNL, n = 9; TL, n = 9; PTL, n = 14) was PCR-amplified using Biolase DNA polymerase (Bioline, Taunton, MA, USA).
TotalRNA was extracted from amnion (TNL, n = 14; TL, n = 34; PTL, n = 59) and decidua (TNL, n = 12; TL, n = 16; PTL, n = 31) tissues using TRIzol reagent (Invitrogen) according to the manufacturer's protocol.
Genome-Wide PaTherns of DNA Methylation and Differentially Methylated CpG Loci between Term (Non-Labored and Labored) and Preterm Amnion Tissues.
We performed the same analysis on one additional gene named oxytocin receptor (OXTR) whose mRNA and protein expression has been shown to be markedly upregulated in association with labor in primary human amnion epithelial cells [18].
For OXTR, since we had no priori data on the methylation status of the 22 CpG sites in amnion tissue, all three groups of samples (TNL, TL, and PTL) were examined.