Human Skeleton Facts

The bones of the human skeleton are living, vital tissue, filled with blood vessels and nutrients that allow them to heal quickly.

Shapes

• Bones come in five shapes: flat bones (sternum, cranial bones), short bones (ankle and wrist bones), long bones (femur, radius, phalanges of fingers and toes), irregular bones (vertebrae, sphenoid) and sesamoid bones, which form in tendons, such as the patella (kneecap).

Function

• Functions of the skeleton include protecting internal organs, assisting in movement by acting as levers for the muscles to pull, maintaining electrolyte balance through storage of calcium and potassium, production of blood cells by bone marrow and energy storage (the fat in yellow bone marrow).

Marrow

• Humans have two types of bone marrow, red and yellow. Yellow is for fat storage, and is found in the appendicular skeleton: the appendages and the pectoral girdle (shoulder blade and clavicle). Red marrow produces blood cells and is found in the axial skeleton: the head, trunk and pelvis, as well as the proximal heads of the femur and humerus.

Identification

• You can identify if a long bone belongs to an adult or child by checking the epiphyseal plate, near where the shaft of the bone meets the head. This is cartilage in children and the site of bone growth. In adults, the cartilage fades and it becomes a faint line.

Remodeling

• Wolff's law of bone says that the structure of a bone is determined by the stress put upon it. Bones are constantly resorbing and laying down new cells along stress lines.