The epiphysis () is the rounded end of a

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 ...

, at its

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

with adjacent bone(s). Between the epiphysis and diaphysis (the long midsection of the long bone) lies the metaphysis, including the

epiphyseal plate The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline cartilage plate in the metaphysis at each end of a long bone. It is the part of a long bone where new bone growth takes place; that is, the whole bone is alive, wit ...

(growth plate). At the joint, the epiphysis is covered with articular cartilage; below that covering is a zone similar to the epiphyseal plate, known as subchondral bone. The epiphysis is filled with red

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

, which produces erythrocytes (red blood cells).

Structure

There are four types of epiphysis: # Pressure epiphysis: The region of the long bone that forms the joint is a pressure epiphysis (e.g. the head of the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates ...

, part of the hip joint complex). Pressure epiphyses assist in transmitting the weight of the human body and are the regions of the bone that are under pressure during movement or locomotion. Another example of a pressure epiphysis is the head of the

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...

which is part of the shoulder complex. condyles of femur and tibia also comes under the pressure epiphysis. # Traction epiphysis: The regions of the long bone which are non-articular, i.e. not involved in joint formation. Unlike pressure epiphyses, these regions do not assist in weight transmission. However, their proximity to the pressure epiphysis region means that the supporting ligaments and tendons attach to these areas of the bone. Traction epiphyses

ossify Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in th ...

later than pressure epiphyses. Examples of traction epiphyses are tubercles of the humerus (greater tubercle and lesser tubercle), and trochanters of the femur (greater and lesser). # Atavistic epiphysis: A bone that is independent phylogenetically but is now fused with another bone. These types of fused bones are called atavistic, ''e.g.'', the

coracoid process The coracoid process (from Greek κόραξ, raven) is a small hook-like structure on the lateral edge of the superior anterior portion of the scapula (hence: coracoid, or "like a raven's beak"). Pointing laterally forward, it, together with t ...

of the scapula, which has been fused in humans, but is separate in four-legged animals. ostrigonum (posterior tubercle of talus ) is another example for atavistic epiphysis. # Aberrant epiphysis: These epiphyses are deviations from the norm and are not always present. For example, the epiphysis at the head of the first metacarpal bone and at the base of other metacarpal bones

Bones with an epiphysis

There are many bones that contain an epiphysis: # Humerus: Located between the shoulder and the elbow. # Radius: One of two bones located between the hand and the elbow. In anatomical position, the radius is lateral to the ulna. # Ulna: One of two bones located between the hand and the elbow. In anatomical position, the ulna is medial to the radius. # Metacarpal: Bones of the hand. They are proximal to the phalanges of the hand. # Phalanges: Bones of the fingers and toes. They are distal to the metacarpals in the hand and metatarsals in the foot. # Femur: Longest bone in the human body. Located in the thigh region, between the hip and the knee. # Fibula: One of two bones in the lower leg. It is lateral to the tibia and smaller. # Tibia: One of two bones in the lower leg. It is medial to the fibula and does most of the weight bearing. # Metatarsal: Bones of the foot. Proximal to the medial

cuneiform Cuneiform is a logo- syllabic script that was used to write several languages of the Ancient Middle East. The script was in active use from the early Bronze Age until the beginning of the Common Era. It is named for the characteristic wedge- ...

on the first metatarsal, and proximal to the phalanges for the other four.

Pseudo-epiphysis

A ''pseudo-epiphysis'' is an epiphysis-looking end of a bone where an epiphysis is not normally located.Page 163
in: A pseudo-epiphysis is delineated by a ''transverse notch'', looking similar to a ''growth plate''. However, these transverse notches lack the typical cell columns found in normal growth plates, and do not contribute significantly to longitudinal bone growth. Pseudo-epiphyses are found at the distal end of the first metacarpal bone in 80% of the normal population, and at the proximal end of the second metacarpal in 60%.

Clinical significance

Pathologies Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...

of the epiphysis include

avascular necrosis Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply. Early on, there may be no symptoms. Gradually joint pain may develop which may limit the ability to move. ...

and osteochondritis dissecans (OCD). OCD involves the subchondral bone. Epiphyseal lesions include

chondroblastoma Chondroblastoma is a rare, benign, locally aggressive bone tumor that typically affects the epiphyses or apophyses of long bones. It is thought to arise from an outgrowth of immature cartilage cells (chondroblasts) from secondary ossification ce ...

and giant-cell tumor.

Additional images

Image:EpiMetaDiaphyse.jpg, Long bone Image:Gray209.png, Longitudinal section of head of left humerus. Image:Illu long bone.jpg

References