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The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a
hyaline cartilage Hyaline cartilage is the glass-like (hyaline) and translucent cartilage found on many joint surfaces. It is also most commonly found in the ribs, nose, larynx, and trachea. Hyaline cartilage is pearl-gray in color, with a firm consistency and h ...
plate in the metaphysis at each 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 ...
. It is the part of a long bone where new bone growth takes place; that is, the whole bone is alive, with maintenance
remodeling Renovation (also called remodeling) is the process of improving broken, damaged, or outdated structures. Renovations are typically done on either commercial or residential buildings. Additionally, renovation can refer to making something new, ...
throughout its existing bone tissue, but the growth plate is the place where the long bone grows longer (adds length). The plate is only found in children and adolescents; in adults, who have stopped growing, the plate is replaced by an
epiphyseal line An epiphyseal line is an epiphyseal plate that has become ossified. The process of it forming from an epiphyseal plate is named epiphyseal closure. In adult humans, it marks the point of fusion between the epiphysis and the metaphysis. Function ...
. This replacement is known as epiphyseal closure or growth plate fusion. Complete fusion can occur as early as 12 for girls (with the most common being 14-15 years for girls) and as early as 14 for boys (with the most common being 15–17 years for boys).


Structure


Development

Endochondral ossification Endochondral ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is produced. Unlike intramembranous ossification, the other process by which bone tissue is produced ...
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 Chondrocytes (, from Greek χόνδρος, ''chondros'' = cartilage + κύτος, ''kytos'' = cell) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteog ...
are under constant division by
mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...
. These daughter cells stack facing the epiphysis while the older cells are pushed towards the diaphysis. As the older chondrocytes degenerate,
osteoblasts Osteoblasts (from the Greek combining forms for " bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts functi ...
ossify the remains to form new bone. In puberty increasing levels of estrogen, in both females and males, leads to increased
apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes in ...
of chondrocytes in the epiphyseal plate. Depletion of chondrocytes due to apoptosis leads to less
ossification 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 ...
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.


Histology

The growth plate has a very specific morphology in having a zonal arrangement as follows:


Clinical significance

Defects in the development and continued division of epiphyseal plates can lead to growth disorders collectively known as osteochondrodysplasia. The most common defect is achondroplasia, where there is a defect in cartilage formation. Achondroplasia is the most common cause of
dwarfism Dwarfism is a condition wherein an organism is exceptionally small, and mostly occurs in the animal kingdom. In humans, it is sometimes defined as an adult height of less than , regardless of sex; the average adult height among people with dw ...
or
short stature Short stature refers to a height of a human which is below typical. Whether a person is considered short depends on the context. Because of the lack of preciseness, there is often disagreement about the degree of shortness that should be called ' ...
and it also manifests in generalized deformities of bones and joints. However, various other types of osteochondrodysplasias can cause short stature and generalized deformities of bones and joints due to abnormal function of growth plate cartilage cells. Hereditary multiple exostoses is a genetic condition that is caused by growth irregularities of the epiphyseal plates of the long bones of the upper and lower limbs. It usually results in limb deformities and a certain degree of functional limitations. Salter–Harris fractures are fractures involving epiphyseal plates and hence tend to interfere with growth, height or physiologic functions. Osgood-Schlatter disease results from stress on the epiphyseal plate in the
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it conn ...
, leading to excess bone growth and a painful lump at the knee. There are important clinical implications of the growth plate physiology. For example guided growth surgery, also known as temporary hemi epiphysiodesis is used to achieve correction or straightening of the bone deformities in a variety of pediatric orthopedic disorders such as
Blount's disease Blount's disease (or Blount disease) is a growth disorder of the tibia (shin bone) which causes the lower leg to angle inward, resembling a bowleg. It is also known as "tibia vara". Description and risk factors Blount disease is a growth disorder ...
,
rickets Rickets is a condition that results in weak or soft bones in children, and is caused by either dietary deficiency or genetic causes. Symptoms include bowed legs, stunted growth, bone pain, large forehead, and trouble sleeping. Complications ma ...
,
arthrogryposis Arthrogryposis (AMC) describes congenital joint contracture in two or more areas of the body. It derives its name from Greek, literally meaning "curving of joints" (', "joint"; ', late Latin form of late Greek ', "hooking"). Children born with one ...
multiplex congenita and
osteochondrodysplasias Osteochondrodysplasia is a general term for a disorder of the development (dysplasia) of bone ("osteo") and cartilage ("chondro"). Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia. Non ...
among others. This applies to bone and joint deformities in the coronal – medial/lateral – plane or genu varum/ genu valgum plane and in the
sagittal The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divi ...
– anterior/posterior – plane or knee flexion deformity/ genu recurvatum plane.


Other animals

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."


See also

* Human development (biology) * Salter–Harris fracture


References


External links


Normal bones at GetTheDiagnosis.org
showing the development of epiphyseal plates for different ages and bones. {{Authority control Skeletal system Medical mnemonics