amnion

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Related to amniotic: Amniotic band, Amniotic band syndrome, Amniotic fluid embolism, Amniotic egg, Amniotic membrane

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 ?
makes regenerative amniotic tissue-based products for use in the ophthalmology, optometry, musculoskeletal and wound care markets.
Our objectives were to assess the relationship between phenol biomarker concentrations measured in maternal urine and amniotic fluid collected on the same day, and to study the variability in urinary phenol concentrations over the course of pregnancy.
They found babies who had experienced carrot in their amniotic fluid or mother's milk ate more of the carrot-flavoured cereal.
Dr Paolo De Coppi, UCL Institute of Child Health, who led the study, said, "Stem cells are well known to have anti-inflammatory effects, but this is the first time we have shown that amniotic fluid stem cells can repair damage in the intestines.
Dr Paolo De Coppi, from University College London's Institute of Child Health, who led the study published in the journal Gut, said: "Stem cells are well known to have anti-inflammatory effects, but this is the first time we have shown that amniotic fluid stem cells can repair damage in the intestines.
leak of amniotic fluid as a cause of vaginal wetness in pregnancy.
The cause is still being debated, but the prevailing theory is that the condition results from an anaphylactoid reaction rather than a direct vascular effect of the amniotic fluid, Dr.
pioneered the development and clinical application of regenerative, amniotic tissue-based products.
The intraday imprecision (CV) of the global procedure (extraction and quantification) was estimated on a pool of amniotic fluids extracted 10 times and injected; the CVs were 9% for GAA and 5% for creatine.
The correlation remained significant after adjustment for parity, placenta location, maternal age, gestational age, and amniotic fluid index.
Such enzymes degrade collagen, one of the structural components of the amniotic sac.
Other Prism products include its GyneCath uterine infusion catheter, a minimally invasive device used to help identify causes of abnormal uterine bleeding or infertility, disposable fetal monitor bands which allow patient mobility while assisting in securing fetal monitor placement and the Mityhook, a sterile instrument used to rupture the amniotic sac during childbirth.