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November 26, 2010

Watch the teeth

Filed under: Teeth — stomatlogos @ 1:32 am
Watch the teeth

Teeth

bone formation, located in the oral cavity in humans and most vertebrates chelyustnorotyh (some fish are also in the throat) with the functions of capture, retention of food, its mechanical processing mastication. There are three anatomical parts

Teeth: top, or crown, neck, and root (or roots). The bulk of the

Teeth is,

in the crown is covered,

in a mammal in the neck and root.
Inside the teeth has a cavity root canal filled tooth pulp, or

.

channel opens at the end of the root apical hole through which the cavity

teeth penetrate blood vessels and nerve fibers.

P In the process of historical development of the animal's teeth came from the skin of teeth, or

,

fish. Incepted

teeth during embryonic development in the form of epithelial folds? Dental records? with the beginnings of the individual teeth are mesenchymal cells of the dermis form below each embryo accumulation (dental papillae) on which the epithelial cells of the dental plates hanging in the form of a cap, so called. enamel organ. The inner layer of cells of dental records involved in the formation of enamel, the outer cells of dental papilla, odontoblasts form dentin and surrounding mesenchymal cells of the cement. Developing

teeth come out, penetrating the mucous membrane of the gums (

Fig. 1 <>).

P The majority of vertebrate teeth to the extent of wear replaced. Change
Teeth is a lifelong polifiodontizm (most vertebrates except mammals), or only once at a young age difiodontizm (most mammals), or not happen at all monofiodontizm (Edentates some mammals, cetaceans). Most fish, reptiles and amphibians, all the teeth are the same (izodontnaya or gomodontnaya system), some fish, reptiles and, as a rule, mammals are

The teeth of different shapes (geterodontnaya system). In cyclostomes develop special

is not homologous teeth chelyustnorotyh vertebrates. The fish

,
Teeth are placed in the soft tissues and bones of the mouth, on the gill arches (<>). There are fish (eg, Vyunova and carp), with only a pharyngeal

Teeth Adult sturgeon do not have the teeth of amphibian teeth are located on the bones of the mouth. In reptiles

Teeth mostly adheres to the jaws (to their edge or inner side), and rarely are on other bones of the mouth. Do crocodiles

The teeth are placed in the wells of the alveoli jaws. Do poisonous snakes in the upper jaw develops poisonous

teeth fitted with channels associated with poisonous

Now living turtles have teeth: their function is performed by cutting edge horn covers the jaw. Modern birds <>> Teeth denied; fossil bird (Archaeopteryx, ihtiornis and others) had

teeth, jaws located in the alveoli. In mammals,

The teeth sit in the alveoli of jaws. No

teeth in adults some edentate, with single-pass, a toothless whales.
P front teeth incisors (1 through 5 pairs in each half of the upper and lower jaw) dolotovidnoy forms are used for grasping and cutting the food, they are followed by canines (1 pair) cones, are used for grasping and tearing food (at prey) and are an instrument of protection (for omnivores and twin-solipeds, some pinnipeds and cetaceans). Hind

Teeth root (up to 8 pairs), have a complex shape and are used for grinding food, and among indigenous distinguish premolars, or lozhnokorennye (34 pairs), and the truly indigenous (34 pairs), equipped with 2 or more roots. Shape and number <>> teeth of various species of mammals, more or less constant and is an important systematic feature. The composition and number

Teeth in mammals is usually expressed dental formula, which usually indicate the number of

teeth in one half of the top (numerator) and bottom (denominator) jaw. Thus, the dental formula dogs:

P where i incisors (incisivi), with fangs (canini), pm lozhnokorennye (praemolares), m istinnokorennye (molares), the total number of

Teeth 44. The initial letters of the Latin names are usually omitted:

P Y number of predatory teeth does not exceed 44; guy and solipeds, rodents and other number

Teeth vary greatly, some Edentates have 1,820 teeth, and some marsupials to 58; toothed whales Family Delphinidae to 250 teeth depending on the functions of different teeth develop unevenly (eg, <>). In carnivorous canines are well developed, rodent incisors and the root, and tusks are lost, and in their place is formed toothless space

Some mammalian teeth grow continuously (eg, rodent incisors). In prosimians and monkeys number

Teeth reduced to 32 (catarrhine monkeys), which coincides with the number <>> teeth in humans.

P BS Matveev.

P A person's teeth, in addition to chewing, biting and holding food, play a major role in pronouncing certain sounds, as well (especially the front) affect the appearance of the face.

The teeth in the jaws are arched.

.

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