Collarbone is a long, slender, curved bone that connects the breastbone with a hooklike projection on the shoulder blade. The technical name for the collarbone is clavicle. The breastbone is properly called the sternum, the hooklike projection, acromion, and the shoulder blade, scapula.
Humans have two collarbones, one to support each shoulder. The bones are shaped somewhat like the italic letter f. They hold the arms in proper position at the sides of the body. When a person breaks a collarbone, the shoulder drops downward and forward toward the chest. Most broken collarbones are caused by falling on the shoulder. A hard blow on the shoulder also may break the collarbone. In addition, such a blow may tear ligaments at the joints between the clavicle, the acromion, and the sternum.
Animals that walk on four legs, such as dogs, have no collarbones. Those that hang from trees, such as apes, have large collarbones. Occasionally, humans are born without collarbones.
