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 has ...
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 bone, short, Flat bone, flat, Irregular bone, irregular and Sesamoid bone, sesamoid. Long bones, especially the femur and tibia, are subj ...
. 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Renovation (also called remodeling) is the process of improving broken, damaged, or outdated structures.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. 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, c ...
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 mainta ...
. 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 language, Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cell (biology), cells with a single Cell nucleus, nucleus that synthesize bone. However, in the p ...
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 incl ...
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 t ...
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
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 ...
. 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 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 fracture
A Salter–Harris fracture is a fracture that involves the epiphyseal plate (growth plate) of a bone, specifically the zone of provisional calcification. It is thus a form of child bone fracture. It is a common injury found in children, occurring ...
s 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 connects ...
, 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,
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 divid ...
– anterior/posterior – plane or knee flexion deformity/
genu recurvatum
Genu recurvatum is a deformity in the knee joint, so that the knee bends backwards. In this deformity, excessive extension occurs in the tibiofemoral joint. Genu recurvatum is also called knee hyperextension and back knee. This deformity is mor ...
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
A Salter–Harris fracture is a fracture that involves the epiphyseal plate (growth plate) of a bone, specifically the zone of provisional calcification. It is thus a form of child bone fracture. It is a common injury found in children, occurring ...
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