They provide both the framework for the body and protection for many delicate internal organs and structures. Other bones, such as those of the limbs, function to provide support and locomotion. Bones of the internal ear structures function for neither protection nor support, but rather for sound transmission, allowing the dog or cat to hear. The bones of the legs grow from areas of immature bone located near the ends. These are called the growth plates, epiphyseal plates or simply the epiphysis.
Growth plates are soft areas of the young bone that grow and add length to the bones.
Growth plates provide growth to the bone until the puppy's or kitten's bone growth is complete, usually by one year of age. At this time the growth plates become hard with calcium and minerals and no longer function as areas of growth. This mineralization is referred to as a closing of the growth plates and indicates the end of significant bone growth. The young unmineralized growth plates are a weak area in the kitten's and puppy's bone and are frequent sites for bone injury or fracture. The primary function of muscles is to bring about movement to all or a part of the dog's or cat's body.