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Blastoderm
A blastoderm (germinal disc, blastodisc) is a single layer of embryonic epithelial tissue that makes up the blastula. It encloses the fluid-filled blastocoel. Gastrulation follows blastoderm formation, where the tips of the blastoderm begins the formation of the ectoderm, mesoderm, and endoderm. Formation The blastoderm is formed when the oocyte plasma membrane begins cleaving by invagination, creating multiple cells that arrange themselves into an outer sleeve to the blastocoel. In oviparous animals In chicken eggs, the blastoderm represents a flat disc after embryonic fertilization. At the edge of the blastoderm is the site of active migration by most cells. DNA repair genes are highly expressed in chicken blastoderms. See also *Blastodisc *Embryology *Cleavage *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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastula
Blastulation is the stage in early animal embryonic development that produces the blastula. In mammalian development, the blastula develops into the blastocyst with a differentiated inner cell mass and an outer trophectoderm. The blastula (from Greek '' βλαστός'' ( meaning ''sprout'')) is a hollow sphere of cells known as blastomeres surrounding an inner fluid-filled cavity called the blastocoel. Embryonic development begins with a sperm fertilizing an egg cell to become a zygote, which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoel is formed does the early embryo become a blastula. The blastula precedes the formation of the gastrula in which the germ layers of the embryo form. A common feature of a vertebrate blastula is that it consists of a layer of blastomeres, known as the blastoderm, which surrounds the blastocoel. In mammals, the blastocyst contains an embryoblast (or inner cell mass) that will eventuall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastula (PSF) En Rotate 05
Blastulation is the stage in early animal embryonic development that produces the blastula. In mammalian development, the blastula develops into the blastocyst with a differentiated inner cell mass and an outer trophectoderm. The blastula (from Greek '' βλαστός'' ( meaning ''sprout'')) is a hollow sphere of cells known as blastomeres surrounding an inner fluid-filled cavity called the blastocoel. Embryonic development begins with a sperm fertilizing an egg cell to become a zygote, which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoel is formed does the early embryo become a blastula. The blastula precedes the formation of the gastrula in which the germ layers of the embryo form. A common feature of a vertebrate blastula is that it consists of a layer of blastomeres, known as the blastoderm, which surrounds the blastocoel. In mammals, the blastocyst contains an embryoblast (or inner cell mass) that will eventually give ris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastocoel
The blastocoel (), also spelled blastocoele and blastocele, and also called cleavage cavity, or segmentation cavity is a fluid-filled or yolk-filled cavity that forms in the blastula during very early embryonic development. At this stage in mammals the blastula is called the blastocyst, which consists of an outer epithelium, the trophectoderm, enveloping the inner cell mass and the blastocoel . It develops following cleavage of the zygote after fertilization. It is the first fluid-filled cavity or lumen formed as the embryo enlarges, and is the essential precursor for the differentiated gastrula. In the ''Xenopus'' a very small cavity has been described in the two-cell stage of development. In mammals After fertilization, the zygote undergoes several rounds of cleavage divisions forming daughter cells known as blastomeres. At the 8- or 16-cell stage, the embryo undergoes compaction and forms the morula. Eventually, the morula is a solid ball of cells that has a small gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germinal Disc
The blastodisc, also called the germinal disc, is the embryo-forming part on the yolk of the egg of an animal that undergoes discoidal meroblastic cleavage. Discoidal cleavage occurs in those animals with a large proportion of yolk in their eggs, and include insects, fish, reptiles and birds. The blastodisc is a small disc of cytoplasm that sits on top of the yolk. In birds, it is a small, circular, white spot (approximately 1.5-3 mm across) on the surface of the yellow yolk of an egg, at the animal pole In developmental biology, an embryo is divided into two hemispheres: the animal pole and the vegetal pole within a blastula. The animal pole consists of small cells that divide rapidly, in contrast with the vegetal pole below it. In some cases, t .... References Early Development in Fish < ... [...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] |
Ectoderm
The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the outer layer of germ cells. The word ectoderm comes from the Greek language, Greek ''ektos'' meaning "outside", and ''derma'' meaning "skin".Gilbert, Scott F. Developmental Biology. 9th ed. Sunderland, MA: Sinauer Associates, 2010: 333-370. Print. Generally speaking, the ectoderm differentiates to form epithelial tissue, epithelial and nervous system, neural tissues (spinal cord, nerves and brain). This includes the Epidermis (skin), skin, linings of the mouth, anus, nostrils, sweat glands, hair and nails, and tooth enamel. Other types of epithelium are derived from the endoderm. In vertebrate embryos, the ectoderm can be divided into two parts: the dorsal surface ectoderm also known as the external ectoderm, and the neural plate, which inv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesoderm
The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical Embryology, 11th edition. 2010. The mesoderm forms mesenchyme, mesothelium and coelomocytes. Mesothelium lines coeloms. Mesoderm forms the muscles in a process known as myogenesis, septa (cross-wise partitions) and mesenteries (length-wise partitions); and forms part of the gonads (the rest being the gametes). Myogenesis is specifically a function of mesenchyme. The mesoderm differentiates from the rest of the embryo through intercellular signaling, after which the mesoderm is polarized by an organizing center. The position of the organizing center is in turn determined by the regions in which beta-catenin is protected from degradation by GSK-3. Beta-catenin acts as a co-factor that alters the activity of the transcription facto ... [...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] |
Oviparous
Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles. Ovoviviparity is a special form of oviparity where the eggs are retained inside the mother (but still metabolically independent), and are carried internally until they hatch and eventually emerge outside as well-developed juveniles similar to viviparous animals. Modes of reproduction The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Repair
DNA repair is a collection of processes by which a cell (biology), cell identifies and corrects damage to the DNA molecules that encode its genome. A weakened capacity for DNA repair is a risk factor for the development of cancer. DNA is constantly modified in Cell (biology), cells, by internal metabolism, metabolic by-products, and by external ionizing radiation, ultraviolet light, and medicines, resulting in spontaneous DNA damage involving tens of thousands of individual molecular lesions per cell per day. DNA modifications can also be programmed. Molecular lesions can cause structural damage to the DNA molecule, and can alter or eliminate the cell's ability for Transcription (biology), transcription and gene expression. Other lesions may induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells following mitosis. Consequently, DNA repair as part of the DNA damage response (DDR) is constantly active. When normal repair proce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastodisc
The blastodisc, also called the germinal disc, is the embryo-forming part on the yolk of the egg of an animal that undergoes discoidal meroblastic cleavage. Discoidal cleavage occurs in those animals with a large proportion of yolk in their eggs, and include insects, fish, reptiles and birds. The blastodisc is a small disc of cytoplasm that sits on top of the yolk. In birds, it is a small, circular, white spot (approximately 1.5-3 mm across) on the surface of the yellow yolk of an egg, at the animal pole In developmental biology, an embryo is divided into two hemispheres: the animal pole and the vegetal pole within a blastula. The animal pole consists of small cells that divide rapidly, in contrast with the vegetal pole below it. In some cases, t .... References Early Development in Fish < ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryology
Embryology (from Ancient Greek, Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logy, -logia'') is the branch of animal biology that studies the Prenatal development (biology), prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology. Early embryology was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the theory that is now accepted, Epigenesis (biology), epigenesis. Epigenesis (biology), Epigenesis is the idea that organisms develop from seed or egg in a sequence of steps. Modern embryology developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance. Comparative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
