| Bone Development Section |
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
| |||||||||||||||||||||||||
The terms osteogenesis and ossification are often used synonymously to indicate the process of
bone formation. Parts of the skeleton form during the first few weeks after conception. By the end
of the eighth week after conception, the skeletal pattern is formed in cartilage and connective tissue
membranes and ossification begins. Bone development continues throughout adulthood.
Even after adult stature is attained, bone development continues for repair of fractures and for
remodeling to meet changing lifestyles. Osteoblasts, osteocytes and osteoclasts are the three cell
types involved in the development, growth and remodeling of bones. Osteoblasts are bone-forming
cells, osteocytes are mature bone cells and osteoclasts break down and reabsorb bone.
There are two types of ossification: intramembranous and endochondral.
Intramembranous:
Intramembranous ossification involves the replacement of sheet-like connective tissue membranes
with bony tissue. Bones formed in this manner are called intramembranous bones. They include
certain flat bones of the skull and some of the irregular bones.
The future bones are first formed as connective tissue membranes. Osteoblasts migrate to the
membranes and deposit bony matrix around themselves. When the osteoblasts are surrounded by
matrix they are called osteocytes.
Endochondral Ossification:
Endochondral ossification involves the replacement of hyaline cartilage with bony tissue. Most of the
bones of the skeleton are formed in this manner. These bones are called endochondral bones. In this
process, the future bones are first formed as hyaline cartilage models.
During the third month after conception, the perichondrium that surrounds the hyaline cartilage
"models" becomes infiltrated with blood vessels and osteoblasts and changes into a periosteum.
The osteoblasts form a collar of compact bone around the diaphysis.
At the same time, the cartilage in the center of the diaphysis begins to disintegrate. Osteoblasts
penetrate the disintegrating cartilage and replace it with spongy bone.
This forms a primary ossification center. Ossification continues from this center toward the ends of
the bones. After spongy bone is formed in the diaphysis, osteoclasts break down the newly formed
bone to open up the medullary cavity.
The cartilage in the epiphyses continues to grow so the developing bone increases in length. Later,
usually after birth, secondary ossification centers form in the epiphyses.
Ossification in the epiphyses is similar to that in the diaphysis except that the spongy bone is
retained instead of being broken down to form a medullary cavity. When secondary ossification is
complete, the hyaline cartilage is totally replaced by bone except in two areas.
A region of hyaline cartilage remains over the surface of the epiphysis as the articular cartilage and
another area of cartilage remains between the epiphysis and diaphysis. This is the epiphyseal plate or
growth region.
Bone Growth:
Bones grow in length at the epiphyseal plate by a process that is similar to endochondral ossification.
The cartilage in the region of the epiphyseal plate next to the epiphysis continues to grow by mitosis.
The chondrocytes, in the region next to the diaphysis, age and degenerate. Osteoblasts move in and
ossify the matrix to form bone.
This process continues throughout childhood and the adolescent years until the cartilage growth
slows and finally stops.
When cartilage growth ceases, usually in the early twenties, the epiphyseal plate completely ossifies
so that only a thin epiphyseal line remains and the bones can no longer grow in length.
Bone growth is under the influence of growth hormone from the anterior pituitary gland and sex
hormones from the ovaries and testes.
bone formation. Parts of the skeleton form during the first few weeks after conception. By the end
of the eighth week after conception, the skeletal pattern is formed in cartilage and connective tissue
membranes and ossification begins. Bone development continues throughout adulthood.
Even after adult stature is attained, bone development continues for repair of fractures and for
remodeling to meet changing lifestyles. Osteoblasts, osteocytes and osteoclasts are the three cell
types involved in the development, growth and remodeling of bones. Osteoblasts are bone-forming
cells, osteocytes are mature bone cells and osteoclasts break down and reabsorb bone.
There are two types of ossification: intramembranous and endochondral.
Intramembranous:
Intramembranous ossification involves the replacement of sheet-like connective tissue membranes
with bony tissue. Bones formed in this manner are called intramembranous bones. They include
certain flat bones of the skull and some of the irregular bones.
The future bones are first formed as connective tissue membranes. Osteoblasts migrate to the
membranes and deposit bony matrix around themselves. When the osteoblasts are surrounded by
matrix they are called osteocytes.
Endochondral Ossification:
Endochondral ossification involves the replacement of hyaline cartilage with bony tissue. Most of the
bones of the skeleton are formed in this manner. These bones are called endochondral bones. In this
process, the future bones are first formed as hyaline cartilage models.
During the third month after conception, the perichondrium that surrounds the hyaline cartilage
"models" becomes infiltrated with blood vessels and osteoblasts and changes into a periosteum.
The osteoblasts form a collar of compact bone around the diaphysis.
At the same time, the cartilage in the center of the diaphysis begins to disintegrate. Osteoblasts
penetrate the disintegrating cartilage and replace it with spongy bone.
This forms a primary ossification center. Ossification continues from this center toward the ends of
the bones. After spongy bone is formed in the diaphysis, osteoclasts break down the newly formed
bone to open up the medullary cavity.
The cartilage in the epiphyses continues to grow so the developing bone increases in length. Later,
usually after birth, secondary ossification centers form in the epiphyses.
Ossification in the epiphyses is similar to that in the diaphysis except that the spongy bone is
retained instead of being broken down to form a medullary cavity. When secondary ossification is
complete, the hyaline cartilage is totally replaced by bone except in two areas.
A region of hyaline cartilage remains over the surface of the epiphysis as the articular cartilage and
another area of cartilage remains between the epiphysis and diaphysis. This is the epiphyseal plate or
growth region.
Bone Growth:
Bones grow in length at the epiphyseal plate by a process that is similar to endochondral ossification.
The cartilage in the region of the epiphyseal plate next to the epiphysis continues to grow by mitosis.
The chondrocytes, in the region next to the diaphysis, age and degenerate. Osteoblasts move in and
ossify the matrix to form bone.
This process continues throughout childhood and the adolescent years until the cartilage growth
slows and finally stops.
When cartilage growth ceases, usually in the early twenties, the epiphyseal plate completely ossifies
so that only a thin epiphyseal line remains and the bones can no longer grow in length.
Bone growth is under the influence of growth hormone from the anterior pituitary gland and sex
hormones from the ovaries and testes.
Even though bones stop growing in length in early adulthood, they can continue to increase in
thickness or diameter throughout life in response to stress from increased muscle activity or to
weight.
The increase in diameter is called appositional growth. Osteoblasts in the periosteum form compact
bone around the external bone surface. At the same time, osteoclasts in the endosteum break down
bone on the internal bone surface, around the medullary cavity.
These two processes together increase the diameter of the bone and, at the same time, keep the
bone from becoming excessively heavy and bulky.
thickness or diameter throughout life in response to stress from increased muscle activity or to
weight.
The increase in diameter is called appositional growth. Osteoblasts in the periosteum form compact
bone around the external bone surface. At the same time, osteoclasts in the endosteum break down
bone on the internal bone surface, around the medullary cavity.
These two processes together increase the diameter of the bone and, at the same time, keep the
bone from becoming excessively heavy and bulky.
|
April 25–28, 2007, the 2nd Conference on Skeletal Biology and Medicine held in NYC.
This meeting, was jointly hosted at the New York Academy of Sciences and Mount Sinai
School of Medicine, was organized and chaired by Mone Zaidi, professor of endocrinology,
geriatrics and adult development, and structural and chemical biology at Mount Sinai. Cochairs were
Gerard Karsenty of Columbia University and Steven Teitelbaum of the Washington University School
of Medicine.
The MHE Research would like to thank all for the use of the presentation on the MHE
Research Foundation website
To view the video presentation given by Dr. Henry Kronenberg during this conference please click
the link tab
This meeting, was jointly hosted at the New York Academy of Sciences and Mount Sinai
School of Medicine, was organized and chaired by Mone Zaidi, professor of endocrinology,
geriatrics and adult development, and structural and chemical biology at Mount Sinai. Cochairs were
Gerard Karsenty of Columbia University and Steven Teitelbaum of the Washington University School
of Medicine.
The MHE Research would like to thank all for the use of the presentation on the MHE
Research Foundation website
To view the video presentation given by Dr. Henry Kronenberg during this conference please click
the link tab
This website is regularly reviewed by members of the Scientific and Medical Advisory Board of the MHE Research Foundation.
Disclaimer: While many find the information useful, it is in no way a substitute for professional medical care.
The information provided here is for educational and informational purposes only. This website does not engage in the practice
of medicine. In all cases we recommend that you consult your own physician regarding any course of treatment or medicine.
The information provided here is for educational and informational purposes only. This website does not engage in the practice
of medicine. In all cases we recommend that you consult your own physician regarding any course of treatment or medicine.
Written consent must be obtained to attach web pages or the files attached to this website. Please email webmaster.
This web page was updated last on 2/20/08, 4:00 pm Eastern time
| Email the webmaster: webmaster@mheresearchfoundation.org Materials on this website are protected by copyright Copyright © 2008 The MHE Research Foundation |
The MHE Research Foundation, we comply with the HONcode standard for health trust worthy information:
By the Health On the Net Foundation. Click here to verify.# HON Conduct 282463 and is linked on the NIH
National Library of Medicine, Directory of Health Organizations (SIS) website, as well as the link for Patient
Information on The Diseases Database a cross-referenced index of human disease, and the Intute: health & life
sciences a free online service providing access to the very best Web resources for education and research
located in the UK
By the Health On the Net Foundation. Click here to verify.# HON Conduct 282463 and is linked on the NIH
National Library of Medicine, Directory of Health Organizations (SIS) website, as well as the link for Patient
Information on The Diseases Database a cross-referenced index of human disease, and the Intute: health & life
sciences a free online service providing access to the very best Web resources for education and research
located in the UK
The MHE Research Foundation is proud to be working with the EuroBoNeT consortium, a European Commission
granted Network of Excellence for studying the pathology and genetics of bone tumors.
granted Network of Excellence for studying the pathology and genetics of bone tumors.
