From Big Medical Encyclopedia

VERTEBRATA [Vertebrata; synonym cranial (Craniota)] — group of the most difficult organized and various animals like chordates.

Items are characterized by considerable development of an autoskeleton, including a backbone and skull, difficult and advanced sense bodys. The body is subdivided not less than into three departments (the head, a trunk, a tail). Covers from ectodermal multilayer epidermis and a corium mesodermal by origin, or dermas (see. Skin ). Also keratinizations of epidermis are usual cover ossification (scales of akulovy and sturgeon fishes, cover bones of a skull, teeth) (a periblast of scales of reptiles, claws, hoofs at mammals). Muscles at the lowest P. accurately metamericly (see. Metamerism ). Performs basic function at P. located around a neurotubule backbone (see). The neurotubule shares on brain (see) and spinal cord (see). The brain consists of 5 departments. The peripheral nervous system is presented by 10 — 12 couples of cranial nerves and metamericly located spinal centers. Water lowest P. have a special system of seismotouch bodies of a sideline remaining at larvae of amphibians. Organs of taste and chemoreceptions are concentrated in an oral cavity (see. Roth, oral cavity ). The partition of functions of chemoreception and sense of smell is expressed completely only at land P., the olfactor organ is covered by cells of an olfactory epithelium. The organ of sight at all P. has essentially similar structure. Acoustic organs and balances are united in a uniform morfol, education. At land P. the sound carrying out device is presented to one (at amphibians, reptiles, birds) or three (at mammals) by acoustical stones. The vestibular mechanism consists of three semicircular channels filled with liquid and the otoliths floating in it transferring pressure upon the feeling cells. At pervichnovodny P. the throat is cut through by branchial apertures, at land P. gills remain only in an embryonal state, and functions of a respiratory organs pass to derivatives of pharyngeal outgrowths — lung (see). The circulatory system closed; in connection with an exit to the land it is divided into arterial and venous departments. At land vertebrata one of pairs of branchiate arteries will be transformed to an aortic arch, other couple — to pulmonary arteries. Eliminative organs — pair kidneys with pair mochevynosyashchy channels. Gonads (ovaries at females, seed plants at males) together with additional glands are tied by output channels with eliminative organs. There are difficult, well developed hemadens.

The chromosomal mechanism of sex determination is characteristic of the highest P. (at mammals — XX for females and XY for males, at birds — ZW for females and ZZ for males; i.e. at mammals a heterogametic sex are males, and at birds — females). Both options of this system of sex determination are inherent to reptiles and amphibians, gonosomes occur at fishes by way of exception, and development of bases of sex is determined by single starting genes.

Due to more complex organization P. in comparison with other chordates the amount of DNA on a genome at them are higher, than at tunicates and at a lancelet. The amount of DNA can strongly vary in different groups and at separate families and childbirth: at Cyclostoma it averages 0,6, at bony — 0,33, at amphipneustic — 35,4, at amphibians having a tail — 15,4, at tailless — 1,34, at reptiles — 0,71, at birds — 0,51, at mammals — on average 0,99 (from amount of DNA on a genome at the person taken for unit).

In total P. share on beschelyustny P., to the Crimea the modern class of Cyclostoma (a lamprey, a miksina) both a class of fossil early Paleozoic armor-clad fishes belongs, and chelyustnoroty, including other P. Chelyustnorotye are divided into the superclass of fishes (including 2 classes — cartilaginous and bony fishes) and a superclass of quadrupeds, or tetrapod, all land vertebrata treat Krom. Tetrapoda on features of embryonic development are divided into two groups — anamniya, to the Crimea the class of amphibians, or amphibiouses, and amniot, the reptiles presented by classes, or reptiles, birds and mammals belongs. The descendants of kistepery fishes who gave rise to amphibians came out of the water. At the same time existence of skin lung respiration and need of an otkladka of caviar for an aqueous medium limited their possibility of a full gain of sushi. The last was completed by amniota — oviparous reptiles. In the Triassic the first appear mammals (see), and in Yura — the first birds, however blossoming of these two classes is necessary on kayonozy.

The person treats P. and kept diverse bonds with other representatives of this subtype. One of characteristic indicators of existence of such bonds is the community of many diseases inherent to different types of P., including infectious.

The section of zoology — zoology of vertebrata is engaged in P.'s studying. Departments of zoology of vertebrata are available in the majority of high fur boots as in our country, and around the world.

Bibliography: Berg L. S. System ryboobrazny and fishes, extant and fossil, M. — L., 1955; Life of animals, under the editorship of L. A. Zenkevich, t. 4 — 6, M., 1969 — 1971; Naumov N. P. and Kartashev N. N. Zoology of vertebrata, p.1 — 2, M., 1979; Ognev S. I. Zoology of vertebrata, M., 1945; Fundamentals of paleontology, under the editorship of Yu. A. Orlov, t. 1 — 15, M., 1958 — 1964; Shmalgauzen I. I. Bases of a comparative anatomy of vertebrate animals, M., 1947; it, Origin of land vertebrata, M., 1964; Cytotaxonomy and vertebrate evolution, ed. by A. B. Chiarelli a. E. Capanna, L., 1973; Traite de paleonto-logie, publ. par J. Piveteau, t. 4—7, P., 1955 — 1964; Traite de zoologie, publ. par P. P. Grasse, t. 12—17, P., 1954 — 1973.

H. H. Vorontsov.