amnion

(redirected from amniotic)
Also found in: Dictionary, Thesaurus, Medical.

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 ?
The device, constructed with bio-inert plastics and 3D-printing techniques, forms a seal with the fetal cavity, enabling gentle and sterile collection of large volumes of amniotic fluid, while being completely safe for mother and baby.
The collection device, which has been constructed with bio-inert plastics and 3D-printing techniques, forms a seal with the fetal cavity, enabling gentle and sterile collection of large volumes of amniotic fluid, while being completely safe for mother and baby.
To test it, the researchers used pieces of a membrane surrounding a cow's heart as an amniotic sac model.
10] Unfortunately, there is no definitive test that confirms the clinical impression of meconium in amniotic fluid or on histopathological specimen.
While many amniotic fluid products advertise stem cell viability, independent research shows that there are few viable stem cells in amniotic fluid.
This experiment was set up to determine the physical properties and chemical composition of amniotic fluid from lateincubation eggs and of different concentrations of a high-quality processed protein supplement, with a view to determine the suitability of the later as a potential IOF supplement for broiler chicks.
Keywords: Amniotic graft, Corneal ulcers, Ocular surface disorders, Re-epithelialisation, Pterygium.
Flake envisions that a decade from now, hospitals will be equipped with chambers filled with artificial amniotic fluid, where premature infants can continue to gestate.
PHYSICIANS' DEFENSE: Further prenatal testing for amniotic fluid levels was unwarranted.
Results: Amniotic and chorionic membranes significantly showed different level of growth inhibitory effects on 8 bacterial strains including seven pathogens: E.
There, the orbs trigger cell death, degrade collagen in the amniotic sac (making it more likely to tear) and can cause inflammation, premature birth and stillbirth.
A number of publications ran almost reverential stories, along with the enchanting YouTube video, about a little unborn Spanish baby who was delivered still inside the intact amniotic sac--moments after its twin was delivered in the normal fashion.