Epiphyseal plate

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Epiphyseal plate
Tib fib growth plates.jpg
Radiogram of distal fibula and tibia showing two epiphyseal plates.
Hypertrophic Zone of Epiphyseal Plate.jpg
Light micrograph of epiphyseal plate showing chondrocytes and matrix.
Latin lamina epiphysialis

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. The plate is found in children and adolescents; in adults, who have stopped growing, the plate is replaced by an epiphyseal line.

Role in bone elongation[edit]

Endochondral ossification is responsible for the initial bone development from cartilage in utero and infants and the longitudinal growth of long bones in the epiphyseal plate. The plate's chondrocytes are under constant division by mitosis. These daughter cells stack facing the epiphysis while the older cells are pushed towards the diaphysis. As the older chondrocytes degenerate, osteoblasts ossify the remains to form new bone. In puberty increasing levels of estrogen, in both males and females, leads to increased apoptosis of chondrocytes in the epiphyseal plate.[1] Depletion of chondrocytes due to apoptosis leads to less ossification and growth slows down and later stops when the entire cartilage have become replaced by bone, leaving only a thin epiphyseal scar which later disappears.[2] Once the adult stage is reached, the only way to manipulate height is modifying bone length via distraction osteogenesis.

Histological organization[edit]

The growth plate has a very specific morphology in having a zonal arrangement.

Epiphyseal plate zone (from epiphysis to diaphysis Description
Zone of reserve Quiescent chondrocytes are found at the epiphyseal end
Zone of proliferation Chondrocytes undergo rapid mitosis under influence of growth hormone
Zone of maturation and hypertrophy Chondrocytes stop mitosis, and begin to hypertrophy by accumulating glycogen, lipids, and alkaline phosphatase
Zone of calcification Chondrocytes undergo apoptosis. Cartilagenous matrix begins to calcify.
Zone of ossification Osteoclasts and osteoblasts from the diaphyseal side break down the calcified cartilage and replace with mineralized bone tissue.

[3]

A mnemonic for remembering the names of the epiphyseal plate growth zones is " Real People Have Career Options," standing for: Resting zone, Proliferative zone, Hypertrophic cartilage zone, Calcified cartilage zone, Ossification zone.[4] The growth plate is clinically relevant in that it is often the primary site for infection, metastasis, fractures and the effects of endocrine bone disorders.[citation needed]

Pathology[edit]

Defects in the development and continued division of epiphyseal plates can lead to growth disorders. The most common defect is achondroplasia, where there is a defect in cartilage formation. Achondroplasia is the most common cause of dwarfism.

Salter–Harris fractures are fractures involving epiphyseal plates and hence tend to interfere with growth and height.

Osgood-Schlatter Disease results from stress on the Epiphyseal plate in the tibia, leading to excess bone growth and a painful lump at the knee.

Studies in animals[edit]

John Hunter studied growing chickens. He observed bones grew at the ends and thus demonstrated the existence of the epiphyseal plates. Hunter is considered the "father of the growth plate".[5]

References[edit]

  1. ^ Zhong, M; Carney, DH; Boyan, BD; Schwartz, Z (January 2011). "17β-Estradiol regulates rat growth plate chondrocyte apoptosis through a mitochondrial pathway not involving nitric oxide or MAPKs.". Endocrinology 152 (1): 82–92. doi:10.1210/en.2010-0509. PMID 21068162. 
  2. ^ "Skeletal System / Bone Development and Growth". Archived from the original on 2008-07-09. Retrieved 2008-07-10. 
  3. ^ Ovalle, William K.; Nahirney, Patrick C. (2007). Netter's essential histology : with Student consult online access (1st ed. ed.). Philadelphia, Pa.: Elsevier Saunders. ISBN 9781929007868. 
  4. ^ "Medical Mnemonics". 
  5. ^ "Growth Plate (Physeal) Fractures". EMedicine.com. Retrieved 2008-01-15. 

See also[edit]