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Reichert's Membrane
Reichert's membrane is an extraembryonic membrane that forms during early mammalian embryonic development. It forms as a thickened basement membrane to cover the embryo immediately following implantation to give protection to the embryo from the uterine pressures exerted. Reichert's membrane is also important for the maternofetal exchange of nutrients. The membrane collapses once the placenta has fully developed. Structure Reichert's membrane is a multilayered, non-vascular, specialised thickened basement membrane that forms on the inner surface of the trophoblast around the time of implantation, and during the formation of the placenta. It is composed of an extracellular matrix that includes laminin, type IV collagen, and nidogen, and is secreted by embryonic cells in the distal parietal endoderm. The synthesis of laminin 111 in the embryo contributes to the formation of Reichert's membrane. Function Reichert's membrane functions as a buffer space between the embryo and the dec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extraembryonic Membrane
The extraembryonic membranes are four membranes which assist in the development of an animal's embryo. Such membranes occur in a range of animals from humans to insects. They originate from the zygote, but are not considered part of the embryo. They typically perform roles in nutrition, gas exchange and waste removal. In amniotes There are four standard extraembryonic membranes in amniote, amniotes, i.e. reptiles (including birds) and mammals: #the yolk sac which surrounds the yolk #the amnion which surrounds and cushions the embryo #the allantois which among avians stores embryonic waste and assists with the exchange of carbon dioxide with oxygen as well as the resorption of calcium from the shell, and #the chorion which surrounds all of these and in avians successively merges with the allantois in the later stages of egg development to form a combined respiratory and excretory organ called the chorioallantois. In humans and other mammals they are more usually called fetal membran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laminin 111
Laminin–111 (also "laminin–1") is a protein of the type known as laminin isoforms. It was among the first of the laminin isoforms to be discovered.Aumailley, M., Bruckner-Tuderman, L., Carter, W. G., Deutzmann, R., Edgar, D., Ekblom, P., & Yurchenco, P. D. (2005). A simplified laminin nomenclature. ''Matrix biology'', 24(5): 326-332. The "111" identifies the isoform's chain composition of α1β1γ1. This protein plays an important role in embryonic development. Injections of this substance are used in treatment for Duchenne muscular dystrophy, and its cellular action may potentially become a focus of study in cancer research. Distribution The distribution of the different laminin isoforms is tissue-specific.Durbeej, M. (2010). Laminins. ''Cell and Tissue Research'', 339(1): 259-268. Laminin–111 is predominantly expressed in the embryonic epithelium, but can also be found in some adult epithelium such as the kidney, liver, testis, ovaries, and brain blood vessels.Ekblom, M., ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placentation
Placentation is the formation, type and structure, or modes of arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases, and water from maternal tissue to a growing embryo, and in some instances to remove waste from the embryo. Placentation is best known in live-bearing mammals (Theria), but also occurs in some fish, reptiles, amphibians, a diversity of invertebrates, and flowering plants. In vertebrates, placentas have evolved more than 100 times independently, with the majority of these instances occurring in squamate reptiles. The placenta can be defined as an organ formed by the sustained apposition or fusion of fetal membranes and parental tissue for physiological exchange. This definition is modified from the original Mossman (1937) definition, which constrained placentation in animals to only those instances where it occurred in the uterus. In mammals In live bearing mammals, the placenta forms after the embryo implants int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amnion
The amnion (: amnions or amnia) is a membrane that closely covers human and various other embryos when they first form. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective environment for the developing embryo. The amnion, along with the chorion, the yolk sac and the allantois protect the embryo. In birds, reptiles and monotremes, the protective sac is enclosed in a shell. In marsupials and placental mammals, it is enclosed in a uterus. The amnion is a feature of the vertebrate clade ''Amniota'', which includes reptiles, birds, and mammals. Amphibians and fish lack the amnion and thus are anamniotes (non-amniotes). The amnion stems from the extra-embryonic somatic mesoderm on the outer side and the extra-embryonic ectoderm or trophoblast on the inner side. Etymology Etymologists have traditionally assumed that the Greek term ἀμνίον (''amnion'') relates to Ancient Greek ἀμνίον : , "little lam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastrulation
Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells), or in mammals, the blastocyst, is reorganized into a two-layered or three-layered embryo known as the gastrula. Before gastrulation, the embryo is a continuous epithelial sheet of cells; by the end of gastrulation, the embryo has begun differentiation to establish distinct cell lineages, set up the basic axes of the body (e.g. dorsal–ventral, anterior–posterior), and internalized one or more cell types, including the prospective gut. Gastrula layers In triploblastic organisms, the gastrula is trilaminar (three-layered). These three germ layers are the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).Mundlos 2009p. 422/ref>McGeady, 2004: p. 34 In diploblastic organisms, such as Cnidaria and Ctenophora, the gastrula has only ectoderm and endoderm. The two layers are also sometimes referred to as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myometrium
The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes) but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions. Structure The myometrium is located between the endometrium (the inner layer of the uterine wall) and the serosa or perimetrium (the outer uterine layer). The myometrium can be divided into three layers: * The inner one-third thickness is termed the ''junctional'' or ''sub-endometrial'' layer. In most mammals it is characterized by fibers oriented in a circular way. Humans, having a single uterus form the fusion of two Müllerian ducts, have the fibers forming two cones. Mice have an unfused uterus, so the arrangement is simply circular. * The middle layer occurs in both mice and humans. In mice it is a hard-to-spot mesh-like structure that probably helps coordinate the forces from the inner and outer layers. In humans there is also a mesh-li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smooth Muscle
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It can be divided into two subgroups, ''single-unit'' and ''multi-unit'' smooth muscle. Within single-unit muscle, the whole bundle or sheet of smooth muscle cells contracts as a syncytium. Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder and uterus. In the walls of blood vessels, and lymph vessels, (excluding blood and lymph capillaries) it is known as vascular smooth muscle. There is smooth muscle in the tracts of the respiratory, urinary, and reproductive systems. In the eyes, the ciliary muscles, iris dilator muscle, and iris sphincter muscle are types of smooth muscles. The iris dilator and s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decidua
The decidua is the modified mucosal lining of the uterus (that is, modified endometrium) that forms every month, in preparation for pregnancy. It is shed off each month when there is no fertilized egg to support. The decidua is under the influence of progesterone. Endometrial cells become highly characteristic. The decidua forms the maternal part of the placenta and remains for the duration of the pregnancy. After birth the decidua is shed together with the placenta. Structure The part of the decidua that interacts with the trophoblast is the ''decidua basalis'' (also called ''decidua placentalis''), while the ''decidua capsularis'' grows over the embryo on the luminal side, enclosing it into the endometrium. The remainder of the decidua is termed the ''decidua parietalis'' or ''decidua vera'', and it will fuse with the decidua capsularis by the fourth month of gestation. Three morphologically distinct layers of the decidua basalis can then be described: * Compact outer layer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryo
An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell. The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres. The blastomeres (4-cell stage) are arranged as a solid ball that when reaching a certain size, called a morula, (16-cell stage) takes in fluid to create a cavity called a blastocoel. The structure is then termed a blastula, or a blastocyst in mammals. The mammalian blastocyst hatches before implantating into the endometrial lining of the womb. Once implanted the embryo will continue its development through the next stages of gastrulation, neurulation, and organogenesis. Gastrulation is the formation of the three germ layers that will form all of the different parts of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endoderm
Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm. The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of multiple systems. In plant biology, endoderm corresponds to the innermost part of the cortex ( bark) in young shoots and young roots often consisting of a single cell layer. As the plant becomes older, more endoderm will lignify. Production The following chart shows the tissues produced by the endoderm. The embryonic endoderm develops into the interior linings of two tubes in the body, the digestive and respiratory tube. Liver and pancreas cells are believed to derive from a common precursor. In humans, the endoderm can differentiate into distinguishable organs after 5 w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryonic Development
In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm, sperm cell (spermatozoon). Once fertilized, the ovum becomes a single diploid cell known as a zygote. The zygote undergoes mitosis, mitotic cell division, divisions with no significant growth (a process known as cleavage (embryo), cleavage) and cellular differentiation, leading to development of a multicellular embryo after passing through an organizational checkpoint during mid-embryogenesis. In mammals, the term refers chiefly to the early stages of prenatal development, whereas the terms fetus and fetal development describe later stages. The main stages of animal embryonic development are as follows: * The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula. * The morula develops into a structure called a bla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nidogen
Nidogens, formerly known as entactins, are a family of sulfated monomeric glycoproteins located in the basal lamina of parahoxozoans. Two nidogens have been identified in humans: nidogen-1 (NID1) and nidogen-2 (NID2). Remarkably, vertebrates are still capable of stabilizing basement membrane in the absence of either identified nidogen. In contrast, those lacking both nidogen-1 and nidogen-2 typically die prematurely during embryonic development as a result of defects existing in the heart and lungs. Nidogen have been shown to play a crucial role during organogenesis in late embryonic development, particularly in cardiac and lung development. Insufficient levels of nidogen in mice causes poorly developed organs such as the lungs and heart, which ultimately ensues to an early death. Due to nidogen being necessary in the formation of basement membranes, serving as a linker protein, and those basement proteins being shown to be necessary during tissue growth, nidogen is crucial for emb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
