The head and neck
The head includes the skull, eyes, ears, muzzle and mouth; its shape differs enormously between breeds, but the bones and organs are the same. The neck connects the head to the trunk and contains the seven cervical vertebrae, the same number in every breed.
The nose leather (planum nasale) is the tip of the nose; behind it, the nasal cavity houses the nasal turbinates that carry the olfactory epithelium, the only place through which the dog perceives smells.
The topline: withers, back, loin, croup
The withers are the highest point of the trunk, between the shoulder blades; beneath them lie the spinous processes of the first thoracic vertebrae. They are the landmark for a dog's height.
The back continues from the withers above the thorax, the loin (lumbar region) is the rib-free portion above the abdomen, and the croup is the area above the pelvis, from its front edge to the root of the tail.
The trunk: thorax, abdomen, tail
The thorax is the box formed by the vertebrae, ribs and sternum, which holds the heart and lungs. The abdomen, with no bones on its sides, houses the stomach, intestines, liver, kidneys, spleen and bladder. The tail continues the spine with 20-23 caudal vertebrae, a number that varies from dog to dog.
The forelimb: shoulder, upper arm, elbow, forearm, carpus, paw
The shoulder contains the shoulder blade; the dog has no functional collarbone, so the forelimb is attached to the trunk only by muscles and ligaments. The upper arm has the humerus, the elbow is the humerus-radius-ulna joint (its point is the olecranon), the forearm has the radius and ulna, the carpus is the wrist with seven bones, and the paw includes the metacarpus, the toes and the pads. The dog walks on its toes: it is digitigrade.
The hind limb: thigh, stifle, lower leg, hock, paw
The thigh has the femur; the knee (stifle) is the femur-tibia-patella joint and sits high, next to the flank; the lower leg has the tibia and fibula; the hock is the tarsal joint, the equivalent of the ankle, with the calcaneus as its point; the hind paw usually has four weight-bearing toes.
The most common confusion: the hock is not a knee. The stifle bends forward, the hock bends backward.
