Epiphysis : definition, types epiphyseal cartilage, growing end

 Epiphysis: it is the parts of a growing long bone which ossify from secondary ossification center.

Types of epiphysis:

Pressure epiphysis: it transmits body weight. Ex:  head of femur

Traction epiphysis: it is produce by pull of muscles EX:  trochanter of femur 

Atavistic epiphysis: coracoid process of scapula. Coracoids process is independent bone unit with scapula for nutrition.

Aberrant epiphyses: This Epiphysis is not always present. For example: the epiphyses at the head of the first metacarpal bone

Epiphyseal cartilage: it is the plate of hyaline cartilage situated between the epiphysis and diaphysis. The plate is found in children and adolescents; In adults, who have stopped growing, the plate is replaced by an epiphyseal line.

One of the steps of Intracartilaginous ossification occurs in epiphyseal cartilage of growing long bone:

Histologically, there are some zone present in epiphyseal cartilage. These zone explain how a bone grow in length.

Zone of reserve No proliferation of chondrocytes

Zone of proliferation Chondrocytes undergo rapid mitosis under influence of growth hormone

Zone of  hypertrophy Chondrocytes stop mitosis, and begin to hypertrophy by accumulating glycogen, lipids, and alkaline phosphatase

Zone of cellular death Cartilagenous matrix begins to calcify- so chondrocytes do not get nutrition-- death of chondrocytes leaving empty spaces.--  Periosteal bud with Blood vessels begin to grow through the empty spaces

Zone of ossification Periosteal buds contain osteoblast which calcify the bone matrix and blood vessel form red bone marrow. This newly form zone of ossification add as metaphysis of growing long bone and bone increase in length

When grow of bone complete the zone of reserve begin to proliferate so whole epiphyseal cartilage converted into bone

Growing end of the long bone: the epiphysis which appear first and unit last with the diaphysis

The growing end is situated against the direction of the nutrient foramen

 Upper end of humerus and lower end of Radius and ulna is the growing end

Lower end of femus and upper end of tibia and fibula is the growing end

Clinical importance: injury or infection of this end makes the bone stunted in growth