Summary of general anatomy of long bone: lecture note

Summary of general anatomy of  long bone

The long bones are those that are longer than they are wide.

They are one of five types of bones: long, short, flat, irregular and sesamoid.

Long bones, especially the femur and tibia, are subjected to most of the load during daily activities and they are crucial for skeletal mobility.

 They grow primarily by elongation of the diaphysis, with an epiphysis at each end of the growing bone. The ends of epiphyses are covered with hyaline cartilage ("articular cartilage").

 The longitudinal growth of long bones is a result of endochondral ossification at the epiphyseal plate.

  The function of long bones is support the weight of the body and facilitate movement.

 Long bones are mostly located in the appendicular skeleton and include bones in the lower limbs (the tibia, fibula, femur, metatarsals, and phalanges) and bones in the upper limbs (the humerus, radius, ulna, metacarpals, and phalanges).

Each long bones consists of a body or shaft and two extremities.

The body, or diaphysis is cylindrical, with a central cavity termed the medullary canal

The wall consists of dense, compact tissue of considerable thickness in the middle part of the body, but becoming thinner toward the extremities; within the medullary canal is some cancellous tissue, scanty in the middle of the body but greater in amount toward the ends.

The extremities are generally expanded, for the purposes of articulation and to afford broad surfaces for muscular attachment.

They are usually developed from separate centers of ossification termed epiphyses, and consist of cancellous tissue surrounded by thin compact bone.

 The medullary canal and the spaces in the cancellous tissue are filled with marrow.

The long bones are not straight, but curved, the curve generally taking place in two planes, thus affording greater strength to the bone.

The bones belonging to this class are: the clavicle, humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, and phalanges.

Clinical anatomy

There are two congenital disorders of the long bones. In a disorder known as rachitis fetalis anularis the ends of the long bones (epiphyses) are enlarged.

 Another disorder is known as rachitis fetalis micromelica in which there is a deficiency in the growth (as a shortness) of the bones

There is a surgical procedure called distraction osteogenesis which is used to lengthen long bones.