Gross Structure Of An Adult Long Bone

Naked eye examination of the longitudinal and transverse sections of a long bone shows the following features:

1. Shaft. From without inwards, it is composed of periosteum cortex and medullary cavity

• Periosteum is a thick fibrous membrane covering the surface of the bone. It is made up of an outer fibrous layer, and an inner cellular layer which is osteogenic in nature. Periosteum is united to the underlying bone by Sharpey’s fibres, and the union is particularly strong over the attachments of tendons and ligaments.

At the articular margin the periosteum is continuous with the capsule of the joint. The abundant periosteal arteries nourish the outer part of the underlying cortex also. Periosteum has a rich nerve supply which makes it the most sensitive part of the bone.

• Cortex is made up of a compact bone which gives it the desired strength to withstand all possible mechanical stains.

• Medullary cavity is filled with red or yellow bone marrow. At birth the marrow is red everywhere with widespread active haemopoiesis. As the age advances the red marrow at many places atrophies and is replaced by yellow, fatty marrow, with no power of haemopoiesis.

Red marrow persists in the cancellous ends of long bones. In the sternum ribs, vertebrae and skull bones the red marrow is found throughout life.

2 The two end of a long bone are made up of cancellous covered with hyaline cartilage.

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4. Parts Of A Young Bone
5. A Look Into The Cells That Constitute Bone