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Encyclopedia > Endochondral ossification
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.)

Endochondral ossification is one of two types of bone formation and is the process responsible for much of the bone growth in vertebrate skeletons, especially in long bones. As the name might suggest (endo - within, chondro - root for cartilage), endochondral ossification occurs by replacement of hyaline cartilage. Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Grays illustration of a human femur, a typically recognized bone. ... Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Tetrapoda Amphibia Amniota Sauropsida/(Reptiles) Aves (Birds) Synapsida Mammalia... In biology, the skeleton or skeletal system is the biological system providing support in living organisms. ... Cartilage is type of dense connective tissue. ...

Contents


Development of the cartilage model

Firstly, mesenchymal cells would crowd together which would result a shape of the future bone, and would futher develop into chondroblasts, which would secrete the cartilage matrix, and finally result a cartilage model which consisting of hyaline cartilage. And perichondrium develops around the cartilage model.


Growth of the cartilage model

The cartilage model would grow in length by continue cell division of chondrocytes, which is accompanied by futher secretion of extracellular matrix. And this is called interstitial growth. And the cartilage model would also grow in thickness which is due to the addition of more extracellular matrix on the periphery cartilage surface, which is accompanied by new chondroblasts that develop form the perichondrium. And this is called apposional growth.


Primary center of ossification

The first site of ossification occurs in the primary center of ossification, which is in the middle of diaphysis (shaft). The following steps then occur: The diaphysis is the main or mid section (shaft) of a long bone. ...

  • Formation of periosteum:Once vascularized, the perichondrium becomes the periosteum. The periosteum contains a layer of undifferentiated cells which later become osteoblasts.
  • Formation of bone collar: The osteoblast secretes osteoid against the shaft of the cartilage model. 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. Nutrients can no longer diffuse if the matrix becomes sufficiently calcified and the chondrocytes subsequently die. This creates cavities within the bone.
  • Invasion of periosteal bud: A periosteal bud, which consists of blood vessels, lymph vessels and nerves, invades the cavity left by the chondrocytes. The vascularization utlimately carries hemopoietic cells, osteoblasts and osteoclasts inside the cavity. The hemopoietic cells will later form the bone marrow.
  • Formation of trabeculae: Osteoblasts use the calcified matrix as a scaffold and begin to secrete osteoid, which forms the bone trabecula. Osteoclasts break down spongy bone to form the medullary (bone marrow) cavity.

The perichondrium is a layer of dense connective tissue which surrounds the cartilage. ... The periosteum is an envelope of fibrous connective tissue that is wrapped around the bone in all places except at joints (which are protected by cartilage). ... An osteoblast (from the Greek words for bone and to build) is a mononucleate cell which produces a protein that produces osteoid. ... Osteoid is a protein mixture which is secreted by osteoblasts. ... Chondrocytes (< Greek chondros cartilage + kytos cell) are the only cells found in cartilage. ... Collagen triple helix. ... Proteoglycans represent a special class of glycoprotein that are heavily glycosylated. ... Alkaline phosphatase, drawn from PDB 1ANI. Alkaline phosphatase (ALP) (EC 3. ... The arterial system The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... In anatomy, lymph vessels are thin walled, valved structures that carry lymph away from the tissues, through the lymph nodes and thoracic duct back to the general circulation. ... Nerves (yellow)    Nerves redirects here. ... Sketch of bone marrow and its cells Pluripotential hemopoietic stem cells (PHSCs) are stem cells found in the bone marrow. ... An osteoblast (from the Greek words for bone and to build) is a mononucleate cell which produces a protein that produces osteoid. ... An osteoclast is a multinucleated cell that degrades and reabsorbs bone. ... Bone marrow (or medulla ossea) is the tissue comprising the center of large bones. ... Osteoid is a protein mixture which is secreted by osteoblasts. ... Definition and etymology trabeculae. ...

Secondary center of ossification

Cartilage is retained in the epiphyseal plate, located between the diaphysis (shaft) and the epiphysis (end) of the bone. These areas of cartilage are known as secondary centers of ossification. Cartilage cells undergo the same transformation as above. As growth progresses, the proliferation of cartilage cells in the epiphyseal plate slows and eventually stops. The continuous replacement of cartilage by bone results in the obliteration of the epiphyseal plate, termed the closure of the epiphysis. Only articular cartilage remains. Mineralisation of articular cartilage and its replacement by bone continues in the adult, though at a much reduced rate than in growing animals. The diaphysis is the main or mid section (shaft) of a long bone. ... For other uses of the word bone, see bone (disambiguation). ...


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. The diaphysis is the main or mid section (shaft) of a long bone. ... The periosteum is an envelope of fibrous connective tissue that is wrapped around the bone in all places except at joints (which are protected by cartilage). ... An osteoclast is a multinucleated cell that degrades and reabsorbs bone. ...


Histology

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.)

During endochondrol ossification, four distinct zones can be seen at the light-microscope level. Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

  1. Zone of resting cartilage. This zone contains normal, resting hyaline cartilage.
  2. Zone of proliferation. In this zone, chondrocytes undergo rapid mitosis, forming dinstinctive looking stacks.
  3. Zone of maturation / hypertrophy. It is during this zone that the chondrocytes undergo hypertrophy (become enlarged). Chondrocytes contain large amounts of glycogen and begin to secrete alkaline phosphatase.
  4. Zone of calcification. In this zone, chondrocytes are either dying or dead, leaving cavities that will later become invaded by bone-forming cells.

Cartilage is type of dense connective tissue. ... Chondrocytes (< Greek chondros cartilage + kytos cell) are the only cells found in cartilage. ... Light micrograph of a newt lung cell in early anaphase of mitosis. ... Electron micrograph of a section of a liver cell showing glycogen deposits as accumulations of electron dense particles (arrows). ... Alkaline phosphatase, drawn from PDB 1ANI. Alkaline phosphatase (ALP) (EC 3. ... Chondrocytes (< Greek chondros cartilage + kytos cell) are the only cells found in cartilage. ...

See also


  Results from FactBites:
 
ITAG - Skull Ossification Discussion, Research Information and Scientific Details (1954 words)
Below is a very detailed scientific discussion about ossification and the human skull, not necessarily as it totally relates to Trepanation, but more for a better understanding as to the overall dynamics of what effects are caused and derived from human bone skull ossification and closing of the cranial sutures.
Endochondral ossification is a bone formation process that begins within (endo) cartilage (chondral).
These bones are formed through endochondral ossification, and for this reason the cranial base is sometimes referred to as the chondrocranium.
Endochondral ossification - Wikipedia, the free encyclopedia (746 words)
During endochondral ossification in the developing fetus, mesenchymal cells aggregate to form a compact grouping of cells in a process called prechondrogenic condensation.
Prechondrogenic condensation begins the process of endochondral ossification and is required for subsequent skeletal development.
The first site of ossification occurs in the primary center of ossification, which is in the middle of diaphysis (shaft).
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