Sunday, March 20, 2011
Bones
In chapter 7, Shubin talks about the different types of cells that make up bones. He says that cartilage is "a perfect pad for our joints. The role of Cartilage cells is to secrete these molecules when the animal is growing and maintain them when the animal is not" (127). Why is it that people get osteoporosis and arthritis if these cells are supposed to be maintained? Is it possible for children to get these diseases, even though the cartilage is supposed to be maintained while animals are still growing? Under what conditions does the cartilage stop/start secreting these molecules?
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First off, cartilage is a bundle of collagenous fibers in a matrix made up of protein, carbohydrates, and collagen. Chondrocytes are the specific cells that secrete collagen and the protein-carbohydrate complex called chondroitin sulfate to make the cartilage flexible yet strong (Campbell 857). One very important theme in the use of cartilage is structure and function. The cartilage is purposely made to be flexible yet strong with collagen so that the movement of the body is supported with the connective tissue breaking apart. The reason for the flexibility of cartilage is to allow smooth movement of the body. The chondrocytes continue to secrete collagen and chondroitin sulfate until the cartilage is ready to be replaced by bone (Encyclopedia Britannica). The collagen and protein-carbohydrate complex expands the cartilage which will be replaced by bone to increase bone size. The secretion of these molecules is most common and intense in fetal development because a large amount of cartilage is needed to increase the size of the bones.
ReplyDeleteOsteoporosis is a condition where the bones thin out because the lack of new bone made while the body absorbs some of the bone tissue. Calcium and vitamin D are essential to prevent osteoporosis because calcium helps maintain the density and thickness of the bone while Vitamin D helps the body absorb calcium (Pubmed Health). In order to create new bone, the calcium, magnesium, and phosphate must combine with collagen from bone-forming cells called osteoblasts to form a hard structure (Campbell). Arthritis, however, is the breakdown of cartilage in the joints that restricts the movements and causes pain to move the joints. The only way for cartilage to break down is if the chondrocytes stop producing the necessary molecules to build cartilage. Arthritis is most prominent in older people and that means that chondrocytes most likely stopped producing as much collagen because there is no need for a lot of collagen in joints. Along with the small amounts of collagen being made, there is the buildup of pressure and constant use of the cartilage within the joints from all the years that results in the slow wear and tear of the cartilage. People with arthritis have a difficult time repairing the cartilage because cartilage lack blood vessels that is necessary for a fast repair and access to nutrients. Chondrocytes receive their nutrients by diffusion which is a much slower process (Encyclopedia Britannica). Another possible cause for arthritis could be that the collagen and chondroitin sulfate between chondrocytes is too dense to allow for efficient diffusion of nutrients from blood vessels through the gel to the chondrocytes. If that were to occur, the chondrocytes would die and no more molecules would be made for the production of cartilage. Although arthritis is most common in adults, juvenile rheumatoid arthritis is an autoimmune disease in children wear the immune systems destroys healthy tissue cells (Pubmed Health). This disease can be caused because of a genetic disorder which means if we know the specific gene that triggers this disease, we can turn “off” that gene so that this disease will not occur. It is very possible that we can apply gene regulation to prevent others from getting this disease. We can stop the transcription of this gene or translation of the proteins that help make the macrophages that destroys healthy tissue cells, but that would mean a lower immunity level for the individual. The positive and negative of this solution must be taken into account to ensure that the individual has sufficient immune to foreign bacteria and viruses.
http://www.school.eb.com/eb/article-41878#470899.hook
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001400/
http://www.school.eb.com/eb/article-9020556?query=cartilage&ct=
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001487/
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ReplyDeleteBenny Jeong
bennyjeong218@gmail.com