Components of a Long Bone - Essay Example

The compact type of bone consists of bony columns parallel to the long axis of the bone, that is, in line with the force exerted on the bone. Every column is composed of lamellae, concentric bony layers, regularly arranged in a manner determined by the distribution of blood vessels, lymphatics, and nerves supplying the bone. These three structures are bundled together in central channels, called Haversian canals, surrounded by lamellae. These canals connect through Volkmann’s canals, which breach them perpendicularly. (Young, 2000)

Spongy bone:
In a long bone, the epiphyses are mainly composed of spongy bone, while on the other hand; in the diaphysis, only a thin layer of spongy bone lines the inner surface of the shaft (immediately surrounding the medullary cavity). This type of bone is composed of a network of irregular bony plates, called trabeculae, separated from each other by a maze of intercommunicating spaces filled with bone marrow. These trabeculae consist of irregular lamellae with lacunae composed of osteocytes, which help in bone nutrition. They are also lined with a fine tissue layer, the endosteum, which contains osteoprogenitor cells, osteoblasts, and osteoclasts. (Young, 2000)

Medullary Cavity:
It is the large central cavity of a long bone that is mostly occupied by spongy bone. In premature beings, the cavities of most bones contain red (active) bone marrow that is responsible for the production of blood cells. In adults, red marrow is found only on specific sites while the rest of the cavity is filled with yellow (inactive) marrow, which is mostly adipose tissue. (Young, 2000)

Nutrient Foramen:
It is the outer opening of the nutrient canal in the shaft of a long bone. It is the point on the bone for the entrance of the nutrient artery, which is responsible for the blood supply to the medullary cavity of the long bone. (OMD, 2000)

Diaphysis:
Ossification progressively spreads from the primary center of ossification, i.e. the center of the long bone, towards the ends of the bone. The part of the long bone that develops from the primary center, that is, the shaft, is known as diaphysis. (Young, 2000)

Epiphyses:
At the secondary centers of ossification, located at the cartilaginous ends of the developing bone, cartilage is replaced by bone in the same way as it occurs at the primary centers. Parts of bone that develop from these centers, that is, the ends, are known as epiphyses. Proximal epiphyses refer to the end that grows towards the primary center, while distal epiphyses refer to the end that grows away from the primary center. (Young, 2000)

Epiphyseal Plate:

It is the plate of cartilage intervening between the diaphysis and epiphyses. This plate is responsible for the elongation of the bone during childhood and early adulthood through the constant proliferation of the cartilage. At maturity, this plate is replaced by bone resulting in the fusion of the epiphyses and diaphysis. (Young, 2000)

Epiphyseal Line:
The junction of the epiphyses and diaphysis indicated later in life by a faint ridge on the outer surface of the long bone is called the Epiphyseal line. (Young, 2000)
Articular Cartilage:
It is a specialized hyaline cartilage that covers the articulating bone surfaces within the joints. Hence, it is responsible for the smooth movement of bones against one another in a joint. (Young, 2000)

Periosteum:
It is a thick fibrous sheath that covers the whole bone except the articular surfaces, into which muscles, tendons, and ligaments are inserted. It has two layers: the fibrous layer which consists of blood vessels, and the cellular layer which is responsible for the reformation of an injured bone. (Young, 2000)

Endosteum:
It is a very thin layer of connective tissue that lines the medullary cavity as well as the canal system of the compact bone. It is composed mainly of reticular cells and fibers, together with fine blood vessels and osteoblasts, responsible for the constant remodeling and growth of bones. (Young, 2000) Read More