Comments Anatomical: A long bone consists of a shaft or diaphysis and two extremities, or epiphyses, and is covered by a vascular membrane, or periosteum. The shaft is made up of compact bone, with a medullary cavity filled with bone marrow. The epiphyses consist of spongy bone coated with compact bone. The shaft is separated from the epiphyses by the epiphyseal cartilages. In the joint, the periosteum is replaced by hyaline cartilage. The shaft is supplied by nutrient arteries and the epiphyses by a capillary network. The sensory nerves enter the bone near the nutrient artery and then divide to spread into the entire bone. Physiological: One of the two layers of the periosteum has a protective role; the other contains osteoblasts and osteoclasts, which take part in remodelling the bone. The osteoblasts form bone; the osteoclasts break it down. Clinical: In cases of trauma or a bony lesion, pain is a warning sign that allows the lesion to be localised and diagnosed. The pain is acute and can become chronic as a result of secondary factors, such as anxiety, sleep disturbances, difficulty moving the affected bone, posttraumatic lesions and damage to nerves. 1. Epiphysis 2. Diaphysis (shaft) 3. Epiphysis 4. Articular (hyaline) cartilage 5. Nutrient artery entering its nutrient foramen 6. Compact bone 7. Medullary cavity (contains yellow marrow) 8. Periosteum 9. Spongy bone (contains red marrow