How Bones Grow in Diameter 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 erosion of old bone along the medullary cavity and the deposition of new bone beneath the periosteum not only increase the diameter of the diaphysis but also increase the diameter of the medullary cavity.
This process is called modeling. The process in which matrix is resorbed on one surface of a bone and deposited on another is known as bone modeling. 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 is resorbed.
Injury, exercise, and other activities lead to remodeling. Those influences are discussed later in the chapter, but even without injury or exercise, about 5 to 10 percent of the skeleton is remodeled annually just by destroying old bone and renewing it with fresh bone.
Skeletal System Osteogenesis imperfecta OI is a genetic disease in which bones do not form properly and therefore are fragile and break easily. It is also called brittle bone disease. The disease is present from birth and affects a person throughout life. The severity of the disease can range from mild to severe. Those with the most severe forms of the disease sustain many more fractures than those with a mild form.
Frequent and multiple fractures typically lead to bone deformities and short stature. Bowing of the long bones and curvature of the spine are also common in people afflicted with OI. Curvature of the spine makes breathing difficult because the lungs are compressed. Because collagen is such an important structural protein in many parts of the body, people with OI may also experience fragile skin, weak muscles, loose joints, easy bruising, frequent nosebleeds, brittle teeth, blue sclera, and hearing loss.
There is no known cure for OI. Treatment focuses on helping the person retain as much independence as possible while minimizing fractures and maximizing mobility. Toward that end, safe exercises, like swimming, in which the body is less likely to experience collisions or compressive forces, are recommended.
Braces to support legs, ankles, knees, and wrists are used as needed. Canes, walkers, or wheelchairs can also help compensate for weaknesses. When bones do break, casts, splints, or wraps are used. In some cases, metal rods may be surgically implanted into the long bones of the arms and legs.
Research is currently being conducted on using bisphosphonates to treat OI. Smoking and being overweight are especially risky in people with OI, since smoking is known to weaken bones, and extra body weight puts additional stress on the bones.
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 hyaline cartilage. Activity in the epiphyseal plate enables bones to grow in length. Modeling allows bones to grow in diameter. Remodeling occurs as bone is resorbed and replaced by new bone. Osteogenesis imperfecta is a genetic disease in which collagen production is altered, resulting in fragile, brittle bones.
In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue, but in endochondral ossification, bone develops by replacing hyaline cartilage. Intramembranous ossification is complete by the end of the adolescent growth spurt, while endochondral ossification lasts into young adulthood. 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.
Considering how a long bone develops, what are the similarities and differences between a primary and a secondary ossification center? A single primary ossification center is present, during endochondral ossification, deep in the periosteal collar. Like the primary ossification center, secondary ossification centers are present during endochondral ossification, but they form later, and there are two of them, one in each epiphysis.
Skip to content Bone Tissue and the Skeletal System. Learning Objectives By the end of this section, you will be able to: Explain the function of cartilage List the steps of intramembranous ossification List the steps of endochondral ossification Explain the growth activity at the epiphyseal plate Compare and contrast the processes of modeling and remodeling.
Cartilage Templates Bone is a replacement tissue; that is, it uses a model tissue on which to lay down its mineral matrix. Intramembranous Ossification During intramembranous ossification , compact and spongy bone develops directly from sheets of mesenchymal undifferentiated connective tissue.
Intramembranous Ossification. Intramembranous ossification follows four steps. When the osteoblasts are surrounded by matrix they are called osteocytes. 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. Skeletal System Osteogenesis imperfecta OI is a genetic disease in which bones do not form properly and therefore are fragile and break easily. It is also called brittle bone disease. The disease is present from birth and affects a person throughout life. The severity of the disease can range from mild to severe. Those with the most severe forms of the disease sustain many more fractures than those with a mild form.
Frequent and multiple fractures typically lead to bone deformities and short stature. Bowing of the long bones and curvature of the spine are also common in people afflicted with OI. Curvature of the spine makes breathing difficult because the lungs are compressed.
Because collagen is such an important structural protein in many parts of the body, people with OI may also experience fragile skin, weak muscles, loose joints, easy bruising, frequent nosebleeds, brittle teeth, blue sclera, and hearing loss.
There is no known cure for OI. Treatment focuses on helping the person retain as much independence as possible while minimizing fractures and maximizing mobility. Toward that end, safe exercises, like swimming, in which the body is less likely to experience collisions or compressive forces, are recommended.
Braces to support legs, ankles, knees, and wrists are used as needed. Canes, walkers, or wheelchairs can also help compensate for weaknesses. When bones do break, casts, splints, or wraps are used. In some cases, metal rods may be surgically implanted into the long bones of the arms and legs. Research is currently being conducted on using bisphosphonates to treat OI. Smoking and being overweight are especially risky in people with OI, since smoking is known to weaken bones, and extra body weight puts additional stress on the bones.
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 hyaline cartilage. Activity in the epiphyseal plate enables bones to grow in length.
Modeling allows bones to grow in diameter. Remodeling occurs as bone is resorbed and replaced by new bone. Osteogenesis imperfecta is a genetic disease in which collagen production is altered, resulting in fragile, brittle bones. In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue, but in endochondral ossification, bone develops by replacing hyaline cartilage.
Intramembranous ossification is complete by the end of the adolescent growth spurt, while endochondral ossification lasts into young adulthood. 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. Considering how a long bone develops, what are the similarities and differences between a primary and a secondary ossification center?
A single primary ossification center is present, during endochondral ossification, deep in the periosteal collar. Like the primary ossification center, secondary ossification centers are present during endochondral ossification, but they form later, and there are two of them, one in each epiphysis. Skip to content Bone Tissue and the Skeletal System. Learning Objectives By the end of this section, you will be able to: Explain the function of cartilage List the steps of intramembranous ossification List the steps of endochondral ossification Explain the growth activity at the epiphyseal plate Compare and contrast the processes of modeling and remodeling.
Cartilage Templates Bone is a replacement tissue; that is, it uses a model tissue on which to lay down its mineral matrix. Intramembranous Ossification During intramembranous ossification , compact and spongy bone develops directly from sheets of mesenchymal undifferentiated connective tissue.
Intramembranous Ossification. Intramembranous ossification follows four steps. Endochondral Ossification In endochondral ossification , bone develops by replacing hyaline cartilage. Endochondral Ossification. Endochondral ossification follows five steps. Perichondrium transforms into periosteum. Periosteal collar develops.
Primary ossification center develops. How Bones Grow in Length The epiphyseal plate is the area of growth in a long bone. Longitudinal Bone Growth. The epiphyseal plate is responsible for longitudinal bone growth.
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