Test 1

Question Answer
what is turbecular? lattice work of bones
What is resorption surface of bones is broken down by osteoclasts, cells that erode the surface of bones
definition and function of bone remodeling coupled process of bone resorption and formation
What are osteocytes? bone cells contain mechanoreceptors/effectors
What are Osteoclasts break down bone and take back the nutrients (resorb bone)
What are Osteoblasts bone builders, bone marrow cells
What kind of cells form osteoclasts? what kind of cells form osteoblasts? Haemopoetic cells form osteoclasts, stromal cells form osteoblasts
What is one way weight lifting helps build bone? Stress the musculature that causes the bone mass to increase
define Osteoporosis the disease characterized by low bone mass, and structural deterioration of bone tissue, Bone fragility, susceptibility for fractures, Porous bone
Explain what happens when blood calcium levels get low in regards to vitamin d parathyroid detects low Ca, secretes PTH, PTH tarkets the kidneys by increasing reabsorption of Ca, & stimulating hydroxylase enzyme to convert calcidiol to calcitriol, the increased D3 and PTH travel to bone stimulating osteoblast increasing resorption
What does an increase of calcitriol do for intestines? the calcitriol goes into the nucleus and increases the expression of the gene that codes for transporters of Ca and vitamin D in and out of the cells
What are the 2 ways vitamin travels in the blood once it is absorbed? Incorporated into chylomicrons (to go to liver 40%) or bound to DBP (extrahepatic tissue 60%)
What fuel is vitamin D absorbed like? and what emulsifying agent is required to break that fuel down releasing vitamin D? lipids, bile acids
vitamin d is mainly absorbed in the: jejunum and ileum
25 hydroxylase converts vitamin D in what form to which form? In which organs does this activity occur? cholecalciferol—-> 25 hydroxycholecalciferol (calcidiol),
liver mainly, lungs, kidneys, intestines
1-hydroxylase converts what to what? What organ is this mainly found? calcidiol—->calcitriol, kidneys
After metabolism and secretion into bile what is the main path of excretion? feces
What is the vitamin d responsive gene? Osteocalcin is vitamin ___ dependent calbindin, vitamin K
Vitamin D has multiple other functions. Name some cell differentiation and proliferation, immune modulation, insulin secretion, neuromuscular function, Ca and P homeostasis, bone mineralization, blood pressure
What are two diseases caused by vitamin d deficiency? rickets: failure of bone to mineralize properly (bowed legs), osteomalacia: failure of bone remineralization during remodeling (painful swelling)
who is at risk of vitamin d deficiency? elderly, infants, malabsorption disorders, disease of the liver kidney intestines or parathyroid
Why is the elderly at risk? less sun exposure and less synthesis of 7 dehydrocholesterol due to less 25 hydroxylase enzyme
What is a good assessment tool for appropriate vitamin d levels? Serum 25(OH)D
What is the risky disease state for vitamin d toxicity? hypercalcemia: vitamin d causes a release of calcium from the bones
What does parathyroid hormone regulate? calcium homeostasis

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