Bones come in different shapes and sizes, each adapted to perform specific functions. The breastbone, for example, is a flat plate of bone that helps to protect the heart and lungs in the chest. The fused bones of the skull safely encase the brain. The short, delicate bones in the wrist and hand enhance dexterity, providing flexibility for small, precise motions. The long, heavy femur bone in the leg acts as a strong lever for powerful or speedy movement. Cartilage is flexible connective tissue that provides support to skeletal bones and allows joints to move without rubbing against each other.
Bone marrow, the soft, pulpy tissue that fills bone cavities, contains a network of blood vessels and fibers surrounded by fat and blood-producing cells. In children, the cells that give rise to blood cells can be found throughout the marrow. In adults, these cells are found mostly in the red marrow of the bones of the chest, hips, back, skull, and of the upper arms and legs. The marrow in the long shafts of bones gradually loses its ability to manufacture blood. This marrow, which is dominated by fat cells and takes on a yellowish color, is called yellow marrow. This cross section of a long bone.
Ligament
Ligament, in anatomy, tough band of slightly elastic connective tissue, made of a fibrous protein known as collagen.
One type of ligament, such as a collateral ligament of the elbow or knee, holds together bones and cartilage at a joint. This white, shiny ligament provides flexibility for freedom of movement and, at the same time, prevents the bones from moving too far apart.
Another type of ligament is thickened