Chapter 6 Course Notes

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1. Compare bone to cartilage tissues relative to its resilience, speed of regeneration and access to nutrients. Bone tissue is composed of mainly of calcium phosphate, making it very hard and resistance to compression, and It regenerates slower in comparison to cartilage. Bone is also a reservoir for minerals and has an interior that forms blood cells. Cartilage contains no blood vessels and relys on the surrounding connective tissue to bring in nutrients.

2. Describe in proper order the events of endochondral ossification. First hyaline cartilage is used as the model for bone construction, then a bone collar is formed around the cartilage. Then the hyaline cartilage is deteriorated so the periosteal bud and spongy bone can begin to form in the interior. The medullary cavity is then formed, as well as a secondary ossification center. Finally when ossification is completed hyaline cartilage remains only in the ends (which promote growth until young adulthood).

3. As we grow, our long bones increase in diameter but the thickness of the compact bone of the shaft remains relatively constant. Explain this phenomenon. Long bones increase in diameter by appositional growth. Osteoblasts secrete bone matrix on the external surface of the bone.

4. Compare and contrast controls of bone remodeling exerted by hormones and by mechanical and gravitational forces, including the actual purpose of each control system and changes in bone architecture that might occur. When calcium gets too low in the blood supply the hormone PTH triggers the osteoclasts (which use lysosomes) to break-down bone, thus releasing minerals back into the blood. If calcium remains too low for too long the bone may begin to resemble having punched out holes in it from the mineral removal. Mechanical stress can also affect bone remodeling, due to fractures and breaks. When a bone is fractured a mass of clotted blood forms at site of the injury. Then a cartilaginous callus forms, which...
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