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Tuesday, June 1, 2010

HUMAN BONE STRUCTURE II - LESSON 201



Now in this lesson we will try to learn about the remaining part of structure of the bone.

The long, relatively straight main body of a long bone, region of primary ossification which is also known as the shaft or middle region of a long bone is called the diaphysis. The end of a each long bone or the regions of secondary ossification is called an epiphysis. The epiphyseal plate is also known as the growth plate or physis. This plate represents an area of cartilage tissue that is constantly being replaced by new bony tissue as the bone grows. 

In a long bone, it is a thin disc of hyaline cartilage that is located transversely between the epiphysis and metaphysis. In the long bones of humans, the epiphyseal plate disappears by the age of twenty. The new bone that is responsible for the lengthening of bones during childhood and adolescence if formed by the cartilage cells at the edges of the epiphyseal plate. When the bone achieved its full growth, the plate calcifies and disappears.

The proximal articular end of the bone is called head. The region of bone between the head the shaft is called neck. 

The periosteum is a strong, fibrous, vascular membrane which covers the surface of a long bone, except at the ends of the epiphyses. Bones other than long bones are completely covered by the periosteum. Beneath the periosteum is the layer of osteoblasts, which deposit calcium phosphate in the bony tissue.

The ends of long bones are covered by a thin layer of cartilage called articular cartilage. This cartilage layer cushions the bones at the place where they meet with other bones joints.

Compact bone is also known as cortical bone is a layer of hard, dense tissue that lies under the periosteum in all bones and chiefly around the diaphysis of a along bones. The blood vessels are located within the compact bone which are the system of small canals that bring oxygen and nutrients to the bone and remove waste products such as carbondioxide. The haversian canals are located in the compact bone. The compact bone is tunneled out in the shaft of the long bones by a central medullary cavity which contains yellow bone marrow. This yellow bone marrow is chiefly composed of fat cells.

In the next post we would try to learn about cancellous bone and the remaining.

Okay.

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