Complete Dog Anatomy Information Guide

Dog Anatomy
A Dog's skeleton is perhaps best described as a framework for the body,   but whilst the bones are alike in terms of the general shape and number, there are  variations which cause the differences in construction and function from breed to breed. Of course, the skeleton of a long, low-legged breed such as the Dachshund is markedly different from that of a Deerhound. Both are hounds, but they have very different functions and so need to be appropriately constructed to suit their breed requirements.

THE SKELETON
However large or small a breed of dog, all have an equal number of bones making up the skeletal structure, with the exception of the bones in the tail. It is the length, thickness, quality and strength of bones which causes breeds to differ, added to which deviations in bone structure can cause dogs within individual breeds to look or to function slightly differently. Surrounding the brain is the skull with deep pockets as protection for eyes and ears, but skulls vary considerably in shape, again according to the breed.

THIRTEEN RIBS
Long ribs form a protective cage around heart, lungs and liver and in a well-constructed dog these need therefore to extend well back along the body. There are nine ribs connected to the sternum by cartilage, three pairs of asternal ribs which join each other at the base, and one pair of floating ribs. Contrary to popular belief, all dogs have these thirteenth, floating ribs which are the shortest of all and remain unattached below. In some dogs, the ends of those ribs are visible, in many it is not. The neck is fitted to the head by a ball and socket joint and the vertebrae extend right along the back to the tip of the tail, but according to the breed there can be between three and 26 vertebrae in the tail itself.

CONSTRUCTION OF THE DOG SKELETON
Perhaps surprisingly, the shoulder blades are not attached to the rest of the skeleton but this is an advantage as it allows for greater flexibility for movement, especially when running. This is especially useful for racing Dogs such as the Greyhound. Below the shoulder blade is the humerus or 'upper arm' which has a knob at its head, preventing the complete straightening of the shoulder joint, thereby limiting the forward reach of the front leg. At the hip, the femur should fit neatly into the pelvis by a ball and socket joint. Elastic tendons, fibrous ligaments and powerful muscles hold the skeleton together; with the joints, each surrounded by a capsule filled with lubricating fluid, acting as shock absorbers.

DOG MOVEMENT
To enable a dog to move in the first place, the brain has to send messages down the spinal cord. These subconscious messages then travel out through peripheral nerves to the various muscles, some instructed to contract, others to relax. Involuntary movements, such as the twitching made by a dog whilst it is sleeping, that makes it look as though it is running, are controlled by the autonomic nervoussystem, another part of the peripheral nervous system. Damage to the spine or peripheral nerves results in the inability of muscles to receive and send messages efficiently, and spastic movement usually indicates damage either to the spinal cord or the brain itself. Muscles can become rigid if blood supply is lost, or they can shrink through lack of use or because there has been damage to the nerve supply. All these factors can be reasons for lack of co-ordination, partial or even complete paralysis.

REGULAR EXERCISE
Exercise as a matter of routine is important for ease of movement. Equally, over-feeding, especially if coupled with under-exercise, results in restricted movement at an early age. In a balanced gait there is complete synchronization between two halves of the body, be it that those two halves are assessed in profile, or from front or rear. The hindquarters provide the propelling or driving force while the forequarters, although they provide support and act as a stabilizer, play a smaller part in the actual propulsion. Of course, to move correctly a dog has to be soundly constructed, but different breeds, by their design, move in differing ways. Although there are some intermediate types of movement, the main gaits are the walk, trot, canter and gallop. A gallop often used by sight hounds amongst others, is the double suspension gallop, a gait in which there are two distinct periods of suspension during the sequence of movement, giving an increase in speed over the normal gallop. It is possible to observe all times when all four legs extended at the same time, and then all legs contracted together. Some gaits are specific to certain breeds. The amble is one in which front and hind legs on the same side move together as a pair, used sometimes when a dog is tired, but seen quite frequently in the Old English Sheepdog when moving at slow speed. The hackney gait, with an exaggerated lift of the front pasterns and feet, is correctly seen in the Miniature Pinscher but is a common fault in the movement of most other breeds.