The femur or thigh bone is the longest bone in the body, extending from the hip and descending down, curving slightly toward the midline of the body until it reaches the knee. It is also the heaviest and strongest bone in the body, yet around 250,000 people experience a broken femur in the U.S. each year. The femur supports the weight of the body during many simple activities including standing, walking, running, and jumping. Not only does the femur account for one-fourth of a person’s height, but it can also resist forces of 1800 to 2500 pounds.
The femur consists of three parts: the proximal, the shaft, and the distal. On the top or proximal end, the femur is part of the ball-and-socket joint, the acetabulum of the hip. At its lower or distal end, the femur forms part of the knee joint. Like other bones in the body, the femur is made up of three layers -- the outside skin or periosteum, a hard compact bone, and the bone marrow, which contains gelatin-like material. These three layers encase both the bloodstream and the nerve signals that move between the layers.
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