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19 Cards in this Set
- Front
- Back
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Briefly describe the composition of bone.
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97% (1/3 weight of bone) of the bone is an organic matrix of collages fibers.
3% (2/3 weight of bone) is ground substance (see PPT) Crystaline salts are deposited in the bone matrix |
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What is bone formation? (How does it happen?)
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Osteoblasts continually lay down the unmineralized bone matrix (mostly collagen)
Osteocytes are mature cells trapped in the lacunae of the matrix which maintain it. Osteoclasts break down the bone matrix. (The relationship between the osteoblasts and osteoclasts are important b/c the old bone becomes weak and brittle and needs to be removed and replaced by new bone. |
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How do osetoblasts become osteocytes?
A Dr. J Question |
An osteocytes is a "trapped" osteoblast. Once an osteoblast becomes surrounded in the matrix it created, it is now an osteocyte.
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What is the function of an osteocyte?
Dr. J Question |
An osteocyte maintains the bone and produces a lot of the chemical needed for bone maintenance.
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What is the function of the osteoclast?
Dr. J Question |
It breaks down the bone, absorbs it, and then the chemicals contained in the bone are then released back into the bloodstream.
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At what age do you build the most bone you're ever going to have?
Dr. J Question |
According to Jody, 30 is considered the upper range when a person builds the most bone in his/her life. After that point, you start losing approx 1% of bone every year and drastically increases after menopause in women.
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What is osteoid?
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It's the matix deposited by osteoblast which contain proteoglycans which contain chondroitin sulfate and collagen fibers.
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What affect does collagen have on bone?
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It gives it compressibility.
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What happens when there is a lack of collagen in the bone?
What disease can happen b/c of this? |
The bone becomes brittle.
Osteogenesis Imperfects "brittle bone disease." |
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Besides bone, why is calcium so important in the body?
Dr J Question |
Calcium is an important mineral for muscle contractions. A lack of calcium could have negative affects on bone, heart muscle, skeletal muscles, breathing trouble b/c problems with respiratory muscles.
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There is a 1:1 correlation between calcium and *blank* in your body.
Dr J Question |
There is a 1:1 correlation between calcium and phosphate in your body.
If you have one more phosphate ion then your kidneys better excrete the extra ion. Your body regulate the balance between the calcium and phosphate rigidly. |
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What determines how you regulate your calcium?
Dr J Question |
It is three things:
PTH (parathyroid hormone) Vitamin D and A Thyroid hormone called calcitonin, which a lot of people take for osteoporosis. |
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What happens if the calcium levels are too low?
Dr J Question |
Your body does not care how much calcium is in your bones; it care how much is in your blood stream.
When Ca++ is low, PTH increases. The PTH hormone does two things: It stimulates osteoclast production in bones to release Ca++ (plus phosphate) back into the blood stream. PTH ALSO increase Vitamin D activation in the kidneys. The vitamin D will also stimulate the osteoclasts in bone to release the CA++ into the blood. It also will cause stomach to absorb more CA++ for the blood stream taken from the food we ingest. This entire process will take more Ca++ away from the bones. |
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What does estrogen have to do with bone?
Dr J Question |
Estrogen acts as a check and balance between PTH and Osteoclasts. Estrogen lessons the osteoclast sensitivity to PTH. When Estroegn is out, the check and balance the osteoclast is more reactive to PTH. It will break down easier when PTH stimulates it.
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What is the relation between high school athletes and anorexic estrogen?
Dr J Question |
Female teenage athletes with very a very lean body mass may not menstruate. Estrogen is a fat soluble molecule and when there is not enough fat, the estrogen will drop and they stop menstruating and will lose bone mass.
Candidates for osteoporosis. |
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What happens when calcium levels are too high?
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Calcitonin increases which stimulates osteoblasts to build bone.
Calcitonin opposes PTH and stimulates osteoblasts to deposit Ca++ in bones. As your calcium levels go up the kidneys need to increase the amount of phosphate being excreted. |
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What's the connection b/t drinking soda and osteoporosis.
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Most sodas and junk food contains high levels of phosphorus. Taking in more phosphorus than your kidneys can excrete will cause calcium levels to go down. This stimulates osteoclast production to take calcium from bone.
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What gives bone it's strength?
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Mineralization of the bone gives bone it's strength.
See notes, but calcium and phosphate and hydroxy(something) crystals mentioned in lecture. |
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What happens when bone is not mineralized or there is a lack of mineralization?
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Children: rickets.
Adults: osteomalcia Disease causing soft bones. Almost exclusively from Vit D deficiency. Can happen in countries w/ women who wear burkas. |
