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The flat bones of the face, most of the cranial bones, and a good deal of the clavicles (collarbones) are formed via intramembranous ossification, while bones at the base of the skull and the long bones form via endochondral ossification.
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- 2019
By the second or third month of fetal life, bone cell development and ossification ramps up and creates the primary ossification center, a region deep in the periosteal collar where ossification begins (Figure \(\PageIndex{2.c}\)).
- Cartilage Templates
- Intramembranous Ossification
- Endochondral Ossification
- How Bones Grow in Length
- How Bones Grow in Diameter
- Bone Remodeling
- Chapter Review
- Critical Thinking Questions
Bone is a replacement tissue; that is, it uses a model tissue on which to lay down its mineral matrix. For skeletal development, the most common template is cartilage. During fetal development, a framework is laid down that determines where bones will form. This framework is a flexible, semi-solid matrix produced by chondroblasts and consists of hy...
During intramembranous ossification, compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue. The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via intramembranous ossification. The process begins when mesenchymal cells in the embryonic skeleton gather...
In endochondral ossification, bone develops by replacinghyaline cartilage. Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification. Bones at the base of the skull and long bones form via endochondral ossification. In ...
The epiphyseal plate is the area of growth in a long bone. It is a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side of the epiphyseal plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, and the diaphysis grows in length. The epiphyseal plate is composed of four zones of cells and ...
While bones are increasing in length, they are also increasing in diameter; growth in diameter can continue even after longitudinal growth ceases. This is called appositional growth. Osteoclasts resorb old bone that lines the medullary cavity, while osteoblasts, via intramembranous ossification, produce new bone tissue beneath the periosteum. The e...
The process in which matrix is resorbed on one surface of a bone and deposited on another is known as bone modeling. Modeling primarily takes place during a bone’s growth. However, in adult life, bone undergoes remodeling, in which resorption of old or damaged bone takes place on the same surface where osteoblasts lay new bone to replace that which...
All bone formation is a replacement process. Embryos develop a cartilaginous skeleton and various membranes. During development, these are replaced by bone during the ossification process. In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue. In endochondral ossification, bone develops by replacing hy...
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Aug 14, 2023 · At birth, the membranous bones are separated from each other by dense connective tissue membranes that form fibrous joints, known as the cranial sutures (coronal, sagittal, and lambdoid). The site at which more than two bones meet are called the fontanelles (anterior, posterior, and two posterolateral).
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Jan 17, 2023 · The formation of bone during the fetal stage of development occurs by two processes: intramembranous ossification and endochondral ossification. Secondary ossification occurs after birth and forms the epiphyses of long bones and the extremities of irregular and flat bones.
Jan 17, 2023 · Embryologic mesenchymal cells differentiate into osteogenic cells that direct bone growth from spicules to trabeculae, to woven bone, and finally to lamellar bone. Endochondral ossification creates fetal long bones from a cartilage template.
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By birth, several areas of cartilage remain in the skeleton, including growth plates at the ends of the long bones. This cartilage grows as the long bones grow, so the bones can keep increasing in length during childhood.
