Hollow Bone

Long bones (Ossa longa) are the most important type of bone.

Examples are on the arm the humerus, ulna and radius and on the leg the femur, tibia and fibula. These are the bones found in the extremities. They are characterised by maximum load-bearing capacity with minimum use of material.

The long bones regularly consist of two bone ends (epiphysis) and the bone shaft (diaphysis). .

The ends of the bones are covered with cartilage so that two bones can move more easily against each other. The bone is surrounded by the so-called periosteum, which has two layers: the inner layer, crossed by blood vessels and nerves, and the outer layer with elastic fibres. The periosteum protects and nourishes the bone via the blood vessels.

https://en.wikipedia.org/wiki/Long_bone