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Amniotic Membrane
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 : , " ... [...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] |
Anamniotes
The anamniotes are an informal group of craniates comprising all fish and amphibians, which lay their eggs in aquatic environments. They are distinguished from the amniotes (reptiles, birds and mammals), which can reproduce on dry land either by laying shelled eggs or by carrying fertilized eggs within the female. Older sources, particularly before the 20th century, may refer to anamniotes as "lower vertebrates" and amniotes as "higher vertebrates", based on the antiquated idea of the evolutionary great chain of being. The name "anamniote" is a back-formation word created by adding the prefix '' an-'' to the word ''amniote'', which in turn refers to the amnion, an extraembryonic membrane present during the amniotes' embryonic development which serves as a biochemical barrier that shields the embryo from environmental fluctuations by regulating the oxygen, carbon dioxide and metabolic waste exchanges and secreting a cushioning fluid. As the name suggests, anamniote embr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anatomical Terms Of Location
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and axes. The meaning of terms that are used can change depending on whether a vertebrate is a biped or a quadruped, due to the difference in the neuraxis, or if an invertebrate is a non-bilaterian. A non-bilaterian has no anterior or posterior surface for example but can still have a descriptor used such as proximal or distal in relation to a body part that is nearest to, or furthest from its middle. International organisations have determined vocabularies that are often used as standards for subdisciplines of anatomy. For example, '' Termi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extraembryonic Coelom
The gestational sac is the large cavity of fluid surrounding the embryo. During early embryogenesis, it consists of the extraembryonic coelom, also called the chorionic cavity. The gestational sac is normally contained within the uterus. It is the only available structure that can be used to determine if an intrauterine pregnancy exists until the embryo can be identified. On obstetric ultrasound, the gestational sac is a dark ( anechoic) space surrounded by a white ( hyperechoic) rim. Structure The gestational sac is spherical in shape, and is usually located in the upper part (fundus) of the uterus. By approximately nine weeks of gestational age, due to folding of the trilaminar germ disc, the amniotic sac expands and occupy the majority of the volume of the gestational sac, eventually reducing the extraembryonic coelom (the gestational sac or the chorionic cavity) to a thin layer between the parietal somatopleuric and visceral splanchnopleuric layer of extraembryonic mesoderm. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ..., fructose, and galactose. Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides; common examples are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose). White sugar is almost pure sucrose. In the body, compound sugars are hydrolysed into simple sugars. Longer chains of monosaccharides (>2) are not regarded as sugars and are called oligosaccharides or polysaccharides. Starch is a glucose polymer found in plants, the most abundant source of energy in human foo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabolic reactions, DNA replication, Cell signaling, responding to stimuli, providing Cytoskeleton, structure to cells and Fibrous protein, organisms, and Intracellular transport, transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the Nucleic acid sequence, nucleotide sequence of their genes, and which usually results in protein folding into a specific Protein structure, 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called pep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelom
The coelom (or celom) is the main body cavity in many animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups. Etymology The term ''coelom'' derives from the Ancient Greek word () 'cavity'. Structure Development The coelom is the mesodermally lined cavity between the gut and the outer body wall. During the development of the embryo, coelom formation begins in the gastrulation stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron. In protostomes, the coelom forms by a process known as schizocoely. The archenteron initially forms, and the mesoderm splits into two layers: the first attaches to the body wall or ectoderm, forming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Somatopleure
In the anatomy of an embryo, the somatopleure is a structure created during embryogenesis when the lateral plate mesoderm splits into two layers. The outer (or somatic) layer becomes applied to the inner surface of the ectoderm, and with it (partially) forms the somatopleure. The combination of ectoderm and mesoderm, or somatopleure, forms the amnion, the chorion and the lateral body wall of the embryo. Limb formation, from the somatic mesoderm, is induced by hox genes and the expression of other molecules through an epithelial-mesenchyme transition. The embryonic somatopleure is then divided into 3 sections, the anterior limb bud formation, the posterior limb bud formation and the non limb forming wall. The bud forming sections grow in size. The somatic mesoderm under the ectoderm proliferates in mesenchyme form. In chicken, the extraembryonic tissues are separated into two layers: the splanchnopleure composed of the endoderm and splanchnic mesoderm, and the somatopleure com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryonic Disk
The bilaminar embryonic disc, bilaminar blastoderm or embryonic disc is the distinct two-layered structure of cells formed in an embryo. In the development of the human embryo this takes place by day eight. It is formed when the inner cell mass, also known as the embryoblast, forms a bilaminar disc of two layers, an upper layer called the epiblast (primitive ectoderm) and a lower layer called the hypoblast (primitive endoderm), which will eventually form into fetus. These two layers of cells are stretched between two fluid-filled cavities at either end: the primitive yolk sac and the amniotic sac. The epiblast is adjacent to the trophoblast and made of columnar epithelial cells; the hypoblast is closest to the blastocoel (blastocystic cavity) and made of cuboidal cells. As the two layers become evident, a basement membrane forms between the layers. This distinction of layers of the bilaminar disc defines the primitive dorso ventral axis and polarity in embryogenesis. The epiblas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amnisos
Amnisos, also Amnissos and Amnisus (Greek language, Greek: or ; Linear B: 𐀀𐀖𐀛𐀰 ''A-mi-ni-so''), is the current but unattested name given to a Bronze Age settlement on the north shore of Crete that was used as a port to the palace city of Knossos. It appears in Greek literature and mythology from the earliest times, but its origin is far earlier, in prehistory. The historic settlement belonged to a civilization now called Minoan civilization, Minoan. Excavations at Amnissos in 1932 uncovered a villa that included the "House of the Lilies", which was named for the lily theme that was depicted in a wall fresco. Geography Amnisos is 7 km east of Heraklion (Iraklio) on a beach used for recreation by the citizens of the modern city. The current sea level is three meters higher than the Bronze Age sea level. The walls of submerged houses are visible from the shore. The ancient settlement bears the same name as the river exiting there. Currently called the Kartero ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eileithyia
Eileithyia or Ilithyia (; ; (''Eleuthyia'') in Crete, also (''Eleuthia'') or (''Elysia'') in Laconia and Messene, and (''Eleuthō'') in literature)Nilsson Vol I, p. 313 was the Greek goddess of childbirth and midwifery, and the daughter of Zeus and Hera. In the cave of Amnisos (Crete) she was related with the annual birth of the divine child, and her cult is connected with ''Enesidaon'' (the earth shaker), who was the chthonic aspect of the god Poseidon. It is possible that her cult is related with the cult of Eleusis. In his ''Seventh Nemean Ode'', Pindar refers to her as the maid to or seated beside the Moirai (Fates) and responsible for the creation of offspring. Her son was Sosipolis, who was worshiped at Elis. Etymology The earliest form of the name is the Mycenaean Greek , ''e-re-u-ti-ja'', written in the Linear B syllabic script. Ilithyia is the latinisation of '. The etymology of the name is uncertain, but debated among scholars. R. S. P. Beekes suggests a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek Dark Ages, Dark Ages (), the Archaic Greece, Archaic or Homeric Greek, Homeric period (), and the Classical Greece, Classical period (). Ancient Greek was the language of Homer and of fifth-century Athens, fifth-century Athenian historians, playwrights, and Ancient Greek philosophy, philosophers. It has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Homeric Greek, Epic and Classical periods of the language, which are the best-attested periods and considered most typical of Ancient Greek. From the Hellenistic period (), Ancient Greek was followed by Koine Greek, which is regar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
