What is Epiphysis?

Epiphysis Definition - Epiphysis is the rounded end of a long bone, its primary function is to connect adjacent bones to form joints. The diaphysis, or shaft, of the long bone, is another prominent feature. There is another part of the long bone between the epiphysis and the diaphysis, which we call metaphysics. The epiphyseal plate, or growth plate of the epiphysis, is found in the metaphysis. At the joint, the epiphysis is also covered by articular cartilage. The subchondral bone, on the other hand, is the bone under the articular cartilage and its growth plate.

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Epiphysis Meaning - It is a part of the bone that ossifies separately and later becomes ankylosed to the main part of the bone especially at the end of the long bone. 

Furthermore, the epiphysis is made up of trabecular tissue, which is a spongy bone. The trabecula, which forms the structural structure of the bone, is the main functional unit of this type of bone tissue. The red bone marrow that undergoes hematopoiesis is found between the trabeculae. Furthermore, the osteoblasts that cover the epiphysis are in charge of converting a spongy bone to compact bone.


Types of Epiphysis 

There are Four Types of the Epiphysis of Bones, Discussed below - 

Pressure Epiphysis: A pressure epiphysis is the portion of the long bone that shapes the joint (e.g. the head of the femur, part of the hip joint complex). Pressure epiphyses are the regions of the bone that are under pressure during movement or locomotion and aid in transmitting the weight of the human body. The head of the humerus, which is part of the shoulder complex, is another example of a pressure epiphysis. The pressure epiphysis also involves the femur of tibia and condyles.

Traction Epiphysis: The non-articular regions of the long bone, which are not involved in joint formation. These areas, unlike pressure epiphyses, do not aid in weight transmission. The supporting ligaments and tendons bind to these areas of the bone due to their proximity to the pressure epiphysis site. Pressure epiphyses ossify first, followed by traction epiphyses. Tubercles of the humerus (greater tubercle and lesser tubercle) and trochanters of the femur are examples of traction epiphyses (greater and lesser).

Atavistic Epiphysis: A phylogenetically independent bone that has been fused with another bone. The coracoid process of the scapula, which has been fused in humans but is distinct in four-legged animals, is an example of atavistic fused bones. Another example of atavistic epiphysis is the os trigonum (posterior tubercle of the talus).

Aberrant Epiphysis: These epiphyses are not necessarily present and are deviated from the standard. The epiphysis at the head of the first metacarpal bone, as well as the epiphysis at the base of other metacarpal bones, are examples.


Pseudo Epiphysis 

A pseudo-epiphysis is an epiphysis-looking end of a bone that isn't really an epiphysis, it is a transverse notch, which resembles a growth plate, defining a pseudo-epiphysis. These transverse notches, on the other hand, lack the usual cell columns found in normal growth plates and thus have little impact on longitudinal bone growth. Pseudo-epiphyses are present in 80 percent of the normal population at the distal end of the first metacarpal bone and 60 percent at the proximal end of the second metacarpal bone.


Bones With an Epiphysis 

There are Many Bones That Contain an Epiphysis:

  1. Humerus - It is located between the shoulder and the elbow.

  2. Radius - Is one of two bones located between the hand and the elbow and its anatomical position is the radius lateral to the ulna.

  3. Ulna - This is one of two bones located between the hand and the elbow and the anatomical position of the ulna is medial to the radius.

  4. Metacarpal - This is the bones of the hand, and they are proximal to the phalanges of the hand.

  5. Phalanges - Is the bones of the fingers and toes and they are distal to the metacarpals in the hand and metatarsals in the foot.

  6. Femur -  It is the longest bone in the human body, and found in the thigh region, between the hip and the knee.

  7. Fibula - This is one of two bones in the lower leg and It is lateral to the tibia and smaller in comparison.

  8. Tibia - This is one of two bones in the lower leg and It is medial to the fibula and does most of the weight-bearing activities in the human body.

  9. Metatarsal - It is the bones of the foot that are proximal to the medial cuneiform on the first metatarsal, and proximal to the phalanges for the other four.


Similarities Between Epiphysis and Diaphysis 

Some of the Similarities Between Epiphysis and Diaphysis are Given below:

  • They are the part of Long bone: epiphysis and diaphysis.

  • All of these sections are made up of bone tissues.

  • Their primary function is to provide shape and support to the animal's skeletal system.

  • They also include osteoblasts and osteoclasts, which are responsible for bone formation.

  • Their matrix is made up of collagen and other proteins, as well as inorganic mineral salts.

  • Nerves, blood vessels, and bone marrow are also found in both.

  • They are also protected by cartilage and membranes such as the endosteum and periosteum.


Difference  Between Diaphysis Epiphysis

Epiphysis 

Diaphysis 

Epiphysis meaning - It is the end part of a long bone, initially growing separate from the shaft. 

Diaphysis meaning - It is the shaft or central part of a long bone.

It makes up the swollen rounded ends of the long bone.

It makes up the long and narrow region of the long bone.

Two epiphyses occur at the proximal and the distal end of the long bone 

Single diaphysis occurs per long bone 

Epiphysis of bone is made up of spongy bone 

The diaphysis of  bone is made of cortical bone 

The functional unit is Trabecula 

The functional unit is the osteon

Contains a marrow cavity 

Lacks a marrow cavity 

Contains a red bone marrow 

Contains a yellow bone marrow 

Contains less amount of calcium 

Contains a higher amount of calcium 

More porous

Less porous

Less strong

More strong

Articulate with other bones forming joints

Provides sites for the attachment of bones


Do You Know?

What are the epiphyseal plate and epiphyseal line? Epiphyseal plate Definition - The epiphyseal plate (also known as the epiphysial plate, physic, or growth plate) is a hyaline cartilage plate found at either end of a long bone in the metaphysis. The growth plate is the portion of a long bone where new bone growth occurs; the whole bone is alive, with maintenance remodeling occurring in its current bone tissue, but the growth plate is where the long bone grows larger (adds length).

Epiphyseal Line Definition - An ossified epiphyseal plate is referred to as an epiphyseal line. Epiphyseal closure is the process by which the formation of an epiphyseal layer takes place. It is the point of fusion between the Epiphysis and the Diaphysis in adult humans.

FAQs (Frequently Asked Questions)

1. What is the Function of the Epiphysis?

Answer. The epiphysis is the section of the long bone where new bone grows. Long bones are formed from the inside out. When the bones need to expand, they force new bone outward from the epiphyseal layer. The epiphyseal plate stops producing cells once the bone has finished developing.

2. What is the Function of the Distal Epiphysis?

Answer. Spongy bone, which is bone with tiny holes close to lattices, makes up the distal epiphysis. The connective tissue and bone marrow cover these gaps. Articular cartilage also covers the distal epiphysis, allowing bones to travel freely at the joints without rubbing against one another.

3. Do Adults have Epiphysis?

Answer. The diaphysis (shaft of primary ossification centre), metaphysis (where the bone flares), physis (or growth plate), and epiphysis (or growth plate) are the four regions of a child's long bone (secondary ossification centre). Only metaphysis and diaphysis are found in adults.

4. What is the difference between Proximal and Distal Epiphysis?

Answer. Epiphyses are large areas on either end of every long bone. The proximal epiphysis is the epiphysis closest to the torso, while the distal epiphysis is at the far end.