Epiphyseal plate
Encyclopedia
The epiphyseal 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.
is responsible for the initial bone development from cartilage in utero
and infants, the epiphyseal plate is responsible for longitudinal growth of bones. 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. Around the end of puberty, the epiphyseal cartilage cells stop duplicating and the entire cartilage is slowly replaced by bone, leaving only a thin epiphyseal line. Once the adult stage is reached, the only way to manipulate height is modifying bone length via distraction osteogenesis
.
The growth plate has a very specific morphology in having a zonal arrangement. The growth plate includes a relatively inactive reserve zone at the epiphyseal end, moving distally into a proliferative and then hypertrophic zone and ending with a band of ossifying cartilage (the metaphysis). 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. 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.
, where there is a defect in cartilage formation. Achondroplasia is the most common cause of dwarfism
.
Salter-Harris fractures
can occur on epiphyseal plates.
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".
Hyaline cartilage
Hyaline cartilage consists of a slimy mass, pearly bluish in colour with firm consistency and considerable collagen. It contains no nerves or blood vessels, and its structure is relatively simple....
plate in the metaphysis
Metaphysis
The metaphysis is the wider portion of a long bone adjacent to the epiphyseal plate. It is this part of the bone that grows during childhood; as it grows, it ossifies near the diaphysis and the epiphyses...
at each end of a long bone
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 and they are crucial for skeletal mobility. They grow...
. 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
Whereas endochondral ossificationEndochondral ossification
Endochondral ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is created. Unlike intramembranous ossification, which is the other process by which bone tissue is created, cartilage is present during endochondral...
is responsible for the initial bone development from cartilage in utero
In utero
In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...
and infants, the epiphyseal plate is responsible for longitudinal growth of bones. The plate's chondrocytes are under constant division by mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
. These daughter cells stack facing the epiphysis
Epiphysis
The epiphysis is the rounded end of a long bone, at its joint with adjacent bone. Between the epiphysis and diaphysis lies the metaphysis, including the epiphyseal plate...
while the older cells are pushed towards the diaphysis
Diaphysis
The diaphysis is the main or mid section of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue ....
. As the older chondrocytes degenerate, osteoblasts ossify the remains to form new bone. Around the end of puberty, the epiphyseal cartilage cells stop duplicating and the entire cartilage is slowly replaced by bone, leaving only a thin epiphyseal line. Once the adult stage is reached, the only way to manipulate height is modifying bone length via distraction osteogenesis
Distraction osteogenesis
Distraction osteogenesis, also called callus distraction, callotasis and osteodistraction is a surgical process used to reconstruct skeletal deformities and lengthen the long bones of the body...
.
The growth plate has a very specific morphology in having a zonal arrangement. The growth plate includes a relatively inactive reserve zone at the epiphyseal end, moving distally into a proliferative and then hypertrophic zone and ending with a band of ossifying cartilage (the metaphysis). 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. 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.
Pathology
Defects in the development and continued division of epiphyseal plates can lead to growth disorders. The most common defect is achondroplasiaAchondroplasia
Achondroplasia dwarfism occurs as a sporadic mutation in approximately 85% of cases or may be inherited in an autosomal dominant genetic disorder that is a common cause of dwarfism...
, where there is a defect in cartilage formation. Achondroplasia is the most common cause of dwarfism
Dwarfism
Dwarfism is short stature resulting from a medical condition. It is sometimes defined as an adult height of less than 4 feet 10 inches , although this definition is problematic because short stature in itself is not a disorder....
.
Salter-Harris fractures
Salter-Harris Fractures
-External links:*...
can occur on epiphyseal plates.
Studies in animals
John HunterJohn Hunter (surgeon)
John Hunter FRS was a Scottish surgeon regarded as one of the most distinguished scientists and surgeons of his day. He was an early advocate of careful observation and scientific method in medicine. The Hunterian Society of London was named in his honour...
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".