Epiphysis

Epiphysis
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Epiphysis Definition

It is a vital growth area near the end of a long bone, which later fuses with the main bone through ossification. It is further divided into proximal, radial and distal sections. It is often mistaken for epiphysis cerebri, a small endocrine gland in the brain. Its plural is epiphyses.

Epiphysis Pronunciation

It is pronounced as e·piph·y·sis.

Epiphysis Location

It is present at the joints.

Epiphysis Description

The end of a long bone is usually swollen and resembles a clenched fist. It is composed of compact or cortical bone on the outside and spongy, or trabecular, bone on the inside. The epiphyseal plate, a hyaline cartilage disk in the wider portion of a long bone, called metaphysis, is situated between the growth site and diaphysis, midsection of the bone. The expanded surface of the semi-rigid, calcified tissue is covered with articular cartilage that separates it from an epiphyseal plate-like structure called subchondral bone.

Epiphysis Types

It is classified into the following types:

Pressure Epiphysis

In this case, the end of the long bone is involved in the formation of joints. It is mainly a secondary center of ossification. Some of its examples are:

  • The head of femur as a component of the hip joint complex
  • The head of humerus, which forms a part of the shoulder complex

Traction Epiphysis

The end portion of the long bone is non-articular in nature. In simple words, it does not form joints. However, its nearness to the articular part of the bone makes the non-ossifying section, a potential site of attachment for supporting ligaments and tendons. In the course of time, the expanded area undergoes ossification. Tubercles of humerus and trochanters of the femur are the typical examples of the non-articular end of long bones.

Atavistic Epiphysis

In this type, the growth end of the bone is a result of fusion of certain bones in the limbs due to evolution. The coracoid process of scapula is one of its common examples.

Aberrant Epiphysis

It is slightly different from the normal structure and does not appear on a frequent basis in the bones. It is most often seen in the head of the first metacarpal bone.

Epiphysis Functions

It is composed of red bone marrow, the main producer of erythrocytes/red blood cells. It also helps in the transmission of weight from areas subjected to tremendous pressure and force. The porous nature of the enlarged section lightens the weight of the bone. In young children, long bones elongate when new cartilage, produced in the epiphyseal plate, is pushed to the edge of the growth site. On the other hand, older cartilages located at the diaphysis get converted into new bones. Growth of the bones usually ceases between the ages of 18 and 25. This phase is usually called epiphyseal closure.

Epiphysis Disorders

The knobby growth end is often prone to slipped capital or subcapital femoral epiphysis, in which the ball of the hip joint separates from the femur. The end region of the inner and larger of the two bones of the lower limb, extending from the knee to the ankle, called tibia, may fracture due to a traumatic force. Fibular epiphyseal fractures are quite common in children. In some cases, the growth end of the calcaneus or heel bone becomes irritated and inflamed, causing extreme pain and restricted movement. The longitudinal epiphyseal bracket is a rare deformity involving the long and short bones of the limbs, resulting in growth defects.

Epiphysis Pictures

Epiphysis Image
Picture 1 – Epiphysis

Epiphysis Picture
Picture 2 – Epiphysis

References

http://en.wikipedia.org/wiki/Epiphysis

http://medical-dictionary.thefreedictionary.com/epiphysis

http://www.skeletalsystem.net/long_bone.php

Last modified on February 16th, 2013 at 1:15 pm

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