Dog Body Structure
The skeleton serves as the framework of the body and provides protection for the organs. The ribs cover the lungs, heart, liver, stomach, kidneys, and pancreas; the skull covers the brain and such delicate organs as the hearing mechanism and the organs of scent.
Each species differs from the next in form; breeds within species differ from other breeds and individual dogs vary in some respects. The skeleton on which the soft tissue of the body hangs is the basic cause of these structural differences. In some dogs, for example, the shortness of certain leg bones can cause a startling difference in appearance contrast the Basset Hound with the Foxhound, the two breeds are alike in all major respects except leg length.
The skeleton is a marvelous framework replete with strength where strength is needed, rigidity where rigidity is needed, flexibility, swivels, and hinges where stretching, bending, and rotating are required. Some bones are solid, others are hollow or filled with marrow in which red blood cells may be generated. Some are mere beads and others long and strong. The way they are joined is an interesting study in itself. There are ball-and-socket joints (hips), hinge joints (knees), others made by one bone abutting on another with a cushion between (vertebrae), and modifications of all three kinds. Some dog arc more agile than others; some have difficulty turning around in a short radius, whereas others, because of their skeletal construction, can “turn on a dime.”
Each long bone is made up of a shaft of hard, brittle material with a soft center of marrow and has ends of spongy material with a covering of dense, hard bone. Around the whole bone is a sort of skin called the periosteum. On top or on the bottom of the spongy end if the bone terminates at a joint is a springy, cartilaginous pad that takes the shocks. All through the bone small spaces form tunnels that carry blood and nerves; nourishment is also furnished by the periosteum.
Some bones are flat: ribs, head bones, and shoulder blades are examples. They are not as solid as they seem but are well fortified with nourishment. The ribs join at the lower extremities with cartilage. These look like true ribs but are only extensions upward from a flat”bone” the sternum, or breastbone to which all but one or two of the last ribs in some species are joined. The sternum is not actually alone but is composed of springy, tough cartilage. The breastbone needs to be flexible, considering the strain it undergoes.
Muscles. Skeletal muscles help hold the framework together, cooperate with it in locomotion and are easily detected beneath the skin. There are two kinds of muscles: the skeletal and the others, not visible outside of the body, called the smooth muscles. When seen under a microscope, fibers of a skeletal muscle appear to have bands or stripes that do not exist on the smooth muscles. The striated muscles are under voluntary control. The duties of the smooth muscles are generally restricted to the functioning of organs and the digestive tract. The gullet, intestines, bladder, blood vessels, and sphincter muscles which act more or less involuntarily, are all smooth.
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