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| Endochondral ossification |
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Light micrograph of epiphyseal plate showing endochondral ossification: healthy chondrocytes (top) become degenerating ones (bottom), characteristically displaying a calcified extracellular matrix.
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| Anatomical terminology
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Endochondral ossification[1][2] 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 ossification. Endochondral ossification is also an essential process during the rudimentary formation of long bones,[3] the growth of the length of long bones,[4] and the natural healing of bone fractures.[5]
Contents
- 1 Growth of the cartilage model
- 2 Primary center of ossification
- 3 Secondary center of ossification
- 4 Appositional bone growth
- 5 Histology
- 6 Fracture healing
- 7 References
- 8 See also
Growth of the cartilage model
The cartilage model will grow in length by continuous cell division of chondrocytes, which is accompanied by further secretion of extracellular matrix. This is called interstitial growth. The process of appositional growth occurs when the cartilage model also grows in thickness due to the addition of more extracellular matrix on the peripheral cartilage surface, which is accompanied by new chondroblasts that develop from the perichondrium.
Primary center of ossification
The first site of ossification occurs in the primary center of ossification, which is in the middle of diaphysis (shaft). Then:
- Formation of periosteum
- The perichondrium becomes the periosteum. The periosteum contains a layer of undifferentiated cells (osteoprogenitor cells) which later become osteoblasts.
- Formation of bone collar
- The osteoblasts secrete osteoid against the shaft of the cartilage model (Appositional Growth). This serves as support for the new bone.
- Calcification of matrix
- Chondrocytes in the primary center of ossification begin to grow (hypertrophy). They stop secreting collagen and other proteoglycans and begin secreting alkaline phosphatase, an enzyme essential for mineral deposition. Then calcification of the matrix occurs and osteoprogenitor cells that entered the cavity via the periosteal bud, use the calcified matrix as a scaffold and begin to secrete osteoid, which forms the bone trabecula. Osteoclasts, formed from macrophages, break down spongy bone to form the medullary (bone marrow) cavity.
Secondary center of ossification
About the time of birth in mammals, a secondary ossification center appears in each end (epiphysis) of long bones. Periosteal buds carry mesenchyme and blood vessels in and the process is similar to that occurring in a primary ossification center. The cartilage between the primary and secondary ossification centers is called the epiphyseal plate, and it continues to form new cartilage, which is replaced by bone, a process that results in an increase in length of the bone. Growth continues until the individual is about 20 years old or until the cartilage in the plate is replaced by bone. The point of union of the primary and secondary ossification centers is called the epiphyseal line.
Appositional bone growth
The growth in diameter of bones around the diaphysis occurs by deposition of bone beneath the periosteum. Osteoclasts in the interior cavity continue to degrade bone until its ultimate thickness is achieved, at which point the rate of formation on the outside and degradation from the inside is constant.
Histology
Drawing of part of a longitudinal section of the developing femur of a rabbit. a. Flattened cartilage cells. b. Enlarged cartilage cells. c, d. Newly formed bone. e. Osteoblasts. f. Giant cells or osteoclasts. g, h. Shrunken cartilage cells. (From “Atlas of Histology,” Klein and Noble Smith.)
Masson Goldner trichrome stain of growth plate in a rabbit tibia.
During endochondral ossification, five distinct zones can be seen at the light-microscope level.
| Name |
Definition |
| Zone of resting cartilage |
This zone contains normal, resting hyaline cartilage. |
| Zone of proliferation / cell columns |
In this zone, chondrocytes undergo rapid mitosis, forming distinctive looking stacks. |
| Zone of maturation / hypertrophy |
In this zone, the chondrocytes undergo hypertrophy (become enlarged). Chondrocytes contain large amounts of glycogen and begin to secrete alkaline phosphatase. |
| Zone of calcification |
In this zone, chondrocytes are either dying or dead, leaving cavities that will later become invaded by bone-forming cells. Chondrocytes here die when they can no longer receive nutrients or eliminate wastes via diffusion. This is because the calcified matrix is much less hydrated than hyaline cartilage. |
| Zone of ossification |
Osteoprogenitor cells invade the area and differentiate into osteoblasts, which elaborate matrix that becomes calcified on the surface of calcified cartilage. This is followed by resorption of the calcified cartilage/calcified bone complex. |
Section of fetal bone of cat. ir. Irruption of the subperiosteal tissue. p. Fibrous layer of the periosteum. o. Layer of osteoblasts. im. Subperiosteal bony deposit. (From Quain’s “Anatomy,” E. A. Schäfer.)
Fracture healing
During fracture healing, cartilage is often formed and is called callus. This cartilage ultimately develops into new bone tissue through the process of endochondral ossification.
References
- ^ Etymology from Greek: ἔνδον/endon, "within", and χόνδρος/chondros, "cartilage"
- ^ "Etymology of the English word endochondral". myEtymology. Retrieved December 2009.
- ^ Netter, Frank H. (1987), Musculoskeletal system: anatomy, physiology, and metabolic disorders. Summit, New Jersey: Ciba-Geigy Corporation ISBN 0-914168-88-6, p. 130: One exception is the clavicle.
- ^ Brighton, Carl T., Yoichi Sugioka, and Robert M. Hunt (1973), "Cytoplasmic structures of epiphyseal plate chondrocytes; quantitative evaluation using electron micrographs of rat costochondral junctions with specific reference to the fate of hypertrophic cells", Journal of Bone and Joint Surgery, 55-A: 771-784
- ^ Brighton, Carl T. and Robert M. Hunt (1986): "Histochemical localization of calcium in the fracture callus with potassium pyroantimonate: possible role of chondrocyte mitochondrial calcium in callus calcification", Journal of Bone and Joint Surgery, 68-A (5): 703-715
See also
- Intramembranous ossification
- Ossification
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Bone and cartilage
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| Cartilage |
- perichondrium
- fibrocartilage callus
- metaphysis
- Cells
- Types
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| Bone |
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Ossification
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- intramembranous
- endochondral
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Cells
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- osteoblast
- osteoid
- osteocyte
- osteoclast
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Types
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Regions
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- subchondral bone
- epiphysis
- epiphyseal plate/metaphysis
- diaphysis
- Condyle
- Epicondyle
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Structure
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- Osteon
- Haversian canals
- Volkmann's canals
- connective tissue
- Sharpey's fibres
- enthesis
- lacunae
- canaliculi
- trabeculae
- medullary cavity
- bone marrow
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Shapes
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- long
- short
- flat
- irregular
- sesamoid
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UpToDate Contents
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English Journal
- Loss of Iroquois homeobox transcription factors 3 and 5 in osteoblasts disrupts cranial mineralization.
- Cain CJ1, Gaborit N2, Lwin W1, Barruet E1, Ho S1, Bonnard C3, Hamamy H4, Shboul M3, Reversade B3, Kayserili H5, Bruneau BG6, Hsiao EC1.
- Bone reports.Bone Rep.2016 Apr 13;5:86-95. doi: 10.1016/j.bonr.2016.02.005. eCollection 2016.
- Cranial malformations are a significant cause of perinatal morbidity and mortality. Iroquois homeobox transcription factors (IRX) are expressed early in bone tissue formation and facilitate patterning and mineralization of the skeleton. Mice lacking Irx5 appear grossly normal, suggesting that redund
- PMID 27453922
- Targeting the hypoxic response in bone tissue engineering: A balance between supply and consumption to improve bone regeneration.
- Stiers PJ1, van Gastel N1, Carmeliet G2.
- Molecular and cellular endocrinology.Mol Cell Endocrinol.2016 Sep 5;432:96-105. doi: 10.1016/j.mce.2015.12.024. Epub 2016 Jan 6.
- Bone tissue engineering is a promising therapeutic alternative for bone grafting of large skeletal defects. It generally comprises an ex vivo engineered combination of a carrier structure, stem/progenitor cells and growth factors. However, the success of these regenerative implants largely depends
- PMID 26768117
- Targeted stimulation of retinoic acid receptor-γ mitigates the formation of heterotopic ossification in an established blast-related traumatic injury model.
- Pavey GJ1, Qureshi AT2, Tomasino AM2, Honnold CL3, Bishop DK4, Agarwal S5, Loder S5, Levi B5, Pacifici M6, Iwamoto M6, Potter BK1, Davis TA7, Forsberg JA1.
- Bone.Bone.2016 Sep;90:159-67. doi: 10.1016/j.bone.2016.06.014. Epub 2016 Jun 28.
- Heterotopic ossification (HO) involves formation of endochondral bone at non-skeletal sites, is prevalent in severely wounded service members, and causes significant complications and delayed rehabilitation. As common prophylactic treatments such as anti-inflammatory drugs and irradiation cannot be
- PMID 27368930
Japanese Journal
- OS1404 関節発生における軟骨内骨化に対する周期的静水圧の影響
- Embryological Consideration of Dural Arteriovenous Fistulas
- Embryological Consideration of Dural Arteriovenous Fistulas
Related Links
- First Known Use of endochondral 1882 Medical Dictionary endochondral play adjective en·do·chon·dral \ˌen-də-ˈkän-drəl\ Medical Definition of endochondral : relating to, formed by, or being ossification that takes place from ...
- endochondral [en″do-kon´dral] situated, formed, or occurring within cartilage. in·tra·car·ti·lag·i·nous (in'tră-kar'ti-laj'i-nŭs), Within a cartilage ... RXR binds to bone morphogenetic proteins (BMP) which substantially affect the process of ...
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