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Lymph Heart
A lymph heart is an organ which pumps lymph in lungfishes, amphibians, reptiles, and flightless birds back into the circulatory system. In some amphibian species, lymph hearts are in pairs, and may number as many as 200 in one animal the size of a worm, while newts and salamanders have as many as 16 to 23 pairs of lymph hearts. Lymph hearts are thought to have evolved in ''Rhipidistia''. Mammals have lost the lymph heart as a centralized organ, instead having the lymph vessel themselves contract to pump lymph. and other amphibians The lymphatic system of a frog consists of lymph, lymph vessels, lymph heart, lymph spaces and spleen. Lymphatics and lymph As lymph is a filtrate of blood, it closely resembles the plasma in its water content. Lymph also contains a small amount of metabolic waste and a much smaller amount of protein than that of blood. Lymph vessels carry the lymph and, in the frog, open into the four lymph hearts. These lymph hearts are located on the dorsal side ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organ (anatomy)
In a multicellular organism, an organ is a collection of Tissue (biology), tissues joined in a structural unit to serve a common function. In the biological organization, hierarchy of life, an organ lies between Tissue (biology), tissue and an organ system. Tissues are formed from same type Cell (biology), cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The Gastrointestinal tract, intestinal wall for example is formed by epithelial tissue and smooth muscle tissue. Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system. An organ's tissues can be broadly categorized as parenchyma, the functional tissue, and stroma (tissue), stroma, the structural tissue with supportive, connective, or ancillary functions. For example, the gland's tissue that makes the hormones is the parenchyma, whereas the stroma includes the nerve t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iliac Vein
In human anatomy, iliac vein refers to several anatomical structures located in the pelvis: * Common iliac vein, formed by the external and internal iliac veins, drains into the inferior vena cava * Deep circumflex iliac vein, formed by the union of the venae comitantes of the deep iliac circumflex artery, and joins the external iliac vein * External iliac vein, terminates at the common iliac vein, drains the femoral vein * Internal iliac vein, terminates at the common iliac vein, drains pelvic organs and perineum * Superficial circumflex iliac vein Superficial circumflex iliac vein is either of the two venae comitantes of the superficial circumflex iliac artery. It usually empties into the great saphenous vein just proximal to where it itself empties into the femoral vein, but may sometimes ... {{DEFAULTSORT:Iliac Vein Perineum Pelvis Veins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinal Column
The spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmented column of vertebrae that surrounds and protects the spinal cord. The vertebrae are separated by intervertebral discs in a series of cartilaginous joints. The dorsal portion of the spinal column houses the spinal canal, an elongated cavity formed by the alignment of the vertebral neural arches that encloses and protects the spinal cord, with spinal nerves exiting via the intervertebral foramina to innervate each body segment. There are around 50,000 species of animals that have a vertebral column. The human spine is one of the most-studied examples, as the general structure of human vertebrae is fairly typical of that found in other mammals, reptiles, and birds. The shape of the vertebral body does, however, vary somewhat b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ratite
Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal extant ratite. The understanding of relationships within the paleognath clade has been in flux. Previously, all the flightless members had been assigned to the order Struthioniformes, which is more recently regarded as containing only the ostrich. The modern bird superorder Palaeognathae consists of ratites and the flighted Neotropic tinamous (compare to Neognathae). Unlike other flightless birds, the ratites have no keel on their sternum—hence the name, from the Latin ('raft', a vessel which has no keel—in contradistinction to extant flighted birds with a keel). Without this to anchor their wing muscles, they could not have flown even if they had developed suitable wings. Ratites are a polyphyletic group; tinamous fall within the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caecilians
Caecilians (; ) are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians among the least familiar amphibians. Modern caecilians live in the tropics of South and Central America, Africa, and southern Asia. Caecilians feed on small subterranean creatures, such as earthworms. The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and a chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves and may contain scales. Modern caecilians are a clade, the order Gymnophiona (or Apoda ), one of the three living amphibian groups alongside Anura (frogs) and Urodela (salamanders). Gymnophiona is a crown group, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turtle
Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked turtles), which differ in the way the head retracts. There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and freshwater terrapins. They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like other Amniote, amniotes (reptiles, birds, and mammals) they breathe air and do not lay eggs underwater, although many species live in or around water. Turtle shells are made mostly of bone; the upper part is the domed Turtle shell#Carapace, carapace, while the underside is the flatter plastron or belly-plate. Its outer surface is covered in scale (anatomy), scales made of keratin, the material of hair, horns, and claws. The carapace bones deve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frogs
A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough skin texture due to wart-like parotoid glands tend to be called toads, but the distinction between frogs and toads is informal and purely cosmetic, not from taxonomy or evolutionary history. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforest and associated wetlands. They account for around 88% of extant amphibian species, and are one of the five most diverse vertebrate orders. The oldest fossil "proto-frog" ''Triadobatrachus'' is known from the Early Triassic of Madagascar (250million years ago), but molecular clock dating suggests their divergence from other amphibians may extend further back to the Permian, 265million years ago. Adult frogs have a st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutionary history, evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, Evolution of birds, having evolved from earlier Theropoda, theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomy (biology), taxonomic, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrapods
A tetrapod (; from Ancient Greek τετρα- ''(tetra-)'' 'four' and πούς ''(poús)'' 'foot') is any four- limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all extant and extinct amphibians and amniotes, with the latter in turn evolving into two major clades, the sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (extinct "pelycosaurs", therapsids and all extant mammals, including humans). Hox gene mutations have resulted in some tetrapods becoming limbless (snakes, legless lizards, and caecilians) or two-limbed (cetaceans, sirenians, some lizards, kiwis, and the extinct moa and elephant birds). Nevertheless, they still qualify as tetrapods through their ancestry, and some retain a pair of vestigial spurs that are remnants of the hindlimbs. Tetrapods evolved from a group of primitive semiaquatic animals known as the tetrapodomorphs which, in turn, evolved from ancient lobe-finned fish ( sarcopterygians) aro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teleost
Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of fish. The Teleostei, which is variously considered a Division (zoology), division or an infraclass in different taxonomic systems, include over 26,000 species that are arranged in about 40 order (biology), orders and 448 family (biology), families. Teleosts range from giant oarfish measuring or more, and ocean sunfish weighing over , to the minute male anglerfish ''Photocorynus spiniceps'', just long. Including not only torpedo-shaped fish built for speed, teleosts can be flattened vertically or horizontally, be elongated cylinders or take specialised shapes as in anglerfish and seahorses. The difference between teleosts and other bony fish lies mainly in their jaw bones; teleosts have a movable premaxilla and corresponding modifications ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MyoD
MyoD, also known as myoblast determination protein 1, is a protein in animals that plays a major role in regulating muscle differentiation. MyoD, which was discovered in the laboratory of Harold M. Weintraub, belongs to a family of proteins known as myogenic regulatory factors (MRFs). These bHLH (basic helix loop helix) transcription factors act sequentially in myogenic differentiation. Vertebrate MRF family members include MyoD1, Myf5, myogenin, and MRF4 (Myf6). In non-vertebrate animals, a single MyoD protein is typically found. MyoD is one of the earliest markers of myogenic commitment. MyoD is expressed at extremely low and essentially undetectable levels in quiescent satellite cells, but expression of MyoD is activated in response to exercise or muscle tissue damage. The effect of MyoD on satellite cells is dose-dependent; high MyoD expression represses cell renewal, promotes terminal differentiation and can induce apoptosis. Although MyoD marks myoblast commitment, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunica Externa
The tunica externa (Neo-Latin "outer coat"), also known as the tunica adventitia (Neo-Latin "additional coat"), is the outermost tunica (biology), tunica (layer) of a blood vessel, surrounding the tunica media. It is mainly composed of collagen and, in arteries, is supported by external elastic lamina. The collagen serves to anchor the blood vessel to nearby organs, giving it stability. The three layers of the blood vessels are: an inner tunica intima, a middle tunica media, and an outer tunica externa. Structure The tunica externa is made from collagen and elastic fibers in a loose connective tissue. This is secreted by fibroblasts. This is normally the thickest tunic in veins and may be thicker than the tunica media in some larger arteries. The outer layers of the tunica externa are not distinct but rather blend with the surrounding connective tissue outside the vessel, helping to hold the vessel in relative position. Function The tunica externa provides basic structural s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
