NTDT401 Lecture Notes - Lecture 17: Myelin, Osteomalacia, Brush Border

• School: University of Delaware
• Department: Nutrition and Dietetics
• Course: NTDT401
• Professor: Fang Richard

Document Summary

In the skin: 7-dehydrocholesterol --> uv light --> previtamin d3 --> foods --> vitamin d3 (inactive form) In the liver: hydroxylation --> 25 hydroxyl vitamin d3. In the kidneys: hydroxylation 1, 25 hydroxyl vitamin d3 (active form) Low blood calcium = activation of vitamin d in calcium. Sufficient amounts of calcitrol or high dietary p intake. Transportation - what form? (as cholecalciferol - blood) 60% = dbp - vitamin d binding protein (skin & diet) Sources of vitamin d: sunlight, animal foods, plants (not a large source) 7-dehydrocholesterol made in sebaceous glands of skin, secreted to surface, then reabsorbed. Exposure to sun = 7-dehydrocholesterol --> previtamin d3 conversion. Dbp-calcitrol binds to receptors and calcitrol is taken up by tissue cells. Hypocalcemia (low ca in blood) stimulates secretion of pth. Pth stimulates 25-oh d3 --> 1,25 oh2 d3 (active) in the kidneys. Calcitrol then acts on target tissues, causing the serum calcium level to increase.