Long bones are a type of bone that is longer than it is wide. They are one of the five major types of bones in the human body and are found in the limbs, fingers, and toes. Some examples of long bones include the femur, tibia, humerus, radius, ulna, metacarpals, and phalanges.
Structure:
Long bones consist of three main parts: the diaphysis, epiphysis, and metaphysis.
Diaphysis: The diaphysis is the long, cylindrical shaft of the bone that provides support and leverage for muscles. It is composed of compact bone, which is dense and hard, and contains the medullary cavity, a hollow space that contains bone marrow.
Epiphysis: The epiphysis is the rounded end of the bone that articulates with another bone to form a joint. It is covered with a layer of hyaline cartilage, which reduces friction and absorbs shock. The epiphysis also contains spongy bone, which is less dense than compact bone and contains red bone marrow, where new blood cells are produced.
Metaphysis: The metaphysis is the transitional region between the diaphysis and epiphysis. It contains a growth plate, which is a layer of hyaline cartilage that allows the bone to grow in length during childhood and adolescence.
Function:
Long bones have several important functions, including:
Support: Long bones provide support for the body and allow for movement by serving as attachment sites for muscles.
Protection: Long bones protect vital organs such as the brain, heart, and lungs. For example, the femur protects the femoral artery, which supplies blood to the lower leg.
Movement: Long bones are involved in movement by acting as levers that are pulled by muscles. For example, the femur acts as a lever that is pulled by the muscles of the thigh to produce movement at the hip joint.
Blood cell production: Red bone marrow within the spongy bone of long bones is responsible for the production of red blood cells, white blood cells, and platelets.
