In the external description of the important systems that make certain features that characterize a particular breed, and belonging to its pedigree group.
In the body of the dog distinguished:
1) The unit of movement — a system of bones, ligaments and muscles.
2) Internal organs — the digestive system, respiratory, urinary and reproductive.
3) integrate the work of all bodies of the system: blood and lymph circulation, immune, endocrine system, the system of the skin, sense organs and nervous system.
To describe the exterior of the dog are important skeletal, skin and musculoskeletal system.

Skeleton.
Skeleton plays an important role in the life of the organism. It serves as a lever movement, support for the soft parts of the body, protected place for the development of the blood, and also participates in metabolic and biochemical processes in the body. Skeleton in their structure peculiar. Distinguishing features of the skeletal system — strength and lightness in comparison with other tissues. In young animal bones are more resilient than the old. With age, bones become more brittle. The skeleton is composed of a dog bone 247 and 262 of the joints. The spine consists of 7 cervical, 13 thoracic, 7 lumbar, 3 sacral, from 3 to 20-23 caudal vertebrae. The axis of the skeleton of a dog is the spinal column, on the front end of which is a skull, and the sides and edges of the limb.
The skull is composed of the facial and cranial bones. Joint attached to the skull lower jaw actuated powerful chewing muscles. The upper and lower jaws are teeth. Adult dogs 42 teeth, puppies — 28 milk teeth. Sometimes a set of teeth can be developed fewer teeth than 42 (oligodontiya), and sometimes there is more teeth (Hyperdontia, giperdontiya). The dog should have a full set of teeth. For individual species typical relative position of teeth in the upper and lower jaws, the so-called bite. Any deviation from the standards in this area has its own name — it can be a pincer bite, undershot bite or bulldog.
Thoracic limb begins with the blade further humerus, forearm, wrist (carpal bones 7) pastern (metacarpus bones 5). Fingers on the end with a strong nevtyazhnymi claws. Thoracic limbs connected with the spine muscles. Above the shoulder blade is formed withers.
Pelvic (rear) limb begins with the femur, tibia moves in (large and fibula), then in the tarsus (composed of 7 bones). After should metatarsus (metatarsals 4-5), then 4 finger metacarpophalangeal ending claws. Sometimes the inner side grows rudimentary (profit) finger. At a young age it is usually amputated. Pelvic limb has articular connection with the pelvis and hip muscles fixed group.

The muscular system.
Plays an important role in the exterior and relief simulates the body of a dog. The mobility and flexibility of the body, the active muscle activity (muscle tendons have little dog) — the distinctive features of the animal. In order to save muscle energy dog ​​prefers not to stand and lie more. For the dog’s movement are particularly important muscles of limbs, back and waist. Equally important are the muscles of the chest and abdomen, providing breathing, and muscles of the head, especially chewing, allowing powerful compression jaws.

Cutaneous system.
Skin that is covered by the dog’s body, consists of three layers: the epidermis, the dermis and subcutaneous tissue. In fact, there are skin follicles, sweaty, aromatic and fat gland capillary vessels and nerve endings. Subcutaneous layer contains fat. In the cuticle grow tufts of hair, each of which contains 3 or more thick and long hairs (guard hairs), which form a coating wool, and 6-12 short delicate hairs (undercoat).
Wool covers almost all of the dog’s body (except for the nose, paw pads of fingers and weak overgrown scrotum in males). Over the eyes, on the cheeks, temples and upper lip are located very long and hard hairs (tactile tentacles). The coat protects the dog from environmental influences. In the spring it is subject to moult and autumn grows warmer fur.
Sweat glands are found in the skin of the paws, this is where the perspiration. That’s why the dog does not sweat all over his body and temperature deviations aligns rapid breathing through an open mouth and evaporation of fluid from the mouth.
In the skin are also aromatic glands that produce the characteristic odor of the dog. Therefore, the dog must from time to time to bathe and wash it by special shampoo.

The nervous system.
Dogs, like all mammals, have developed nervous system, in which the isolated central and peripheral systems. Thanks to the high level of organization of the central nervous system of the dog has developed senses.
The sense of smell in dogs 48 times sharper than a human. It is used for foraging, orientation in space, is one of the means of communication. Dog’s life — a world of smells. No less important role in her life hearing. The upper threshold of hearing in dogs is almost 5 times higher than in humans, which allows it to distinguish between ultrasounds.
Sight most dogs developed worse than smell and hearing. However, some species (eg greyhound) has larger vigilance: they are able to distinguish objects at a distance of 150 meters. The bodies of the dogs are tactile or tactile hairs (vibrissae). They grow on the lower jaw, the upper lip (mustache), above the eyes, on the neck. With their help, the animal is oriented in the dark, determines the direction of the wind.
The organs of taste dogs presented taste buds located on the tongue.

The reproductive system.
Dog reaches sexual maturity in 6-11 months (this period in females first heat). By 15-16 months completed puberty dog. Optimal battery first mating females for 1.5-2 years. Estrus females is 2 times per year (every 6 months); its average duration to 28 days. Pregnancy (lumination) in dogs lasts 59-65 days. Normal births are usually unaided and extend from hours to 6 hours. In litter, usually occurs 2 to 6 puppies.