Bone Physiology Continued

Front 1

Describe the consequences of imbalance of calcium, phosphorus, or both

Back 1

Hypercalcemia:moans, bones, groans, and stones
Hyperphosphatemia: same as those for hypocalcemia, parasthesias, muscle cramps, tetany, QT interval prolongation.
Hyperphosphatemia and hypercalcemia: diffuse visceral deposition of calcium phosphates demonstrable on bone scans
Hypophosphatemia: Global decline in cellular fxn. Neuromuscular signs and sys. Abnormal bone mineralization.

Front 2

Explain why renal failure alters calcium and phosphate regulation

Back 2

they excrete some calcium but also make active VitD. results of renal failure are hypocalcemia. Normally, phosphate is excreted, so result in failure is hyperphosphatemia

Front 3

explain how bone is remodeled and the roles of osteoblasts and osteoclasts

Back 3

as haversian systems are resorbed, osteocytes die and osteoclasts are recruited to the area to resorb the bone matrix, forming absorption cavities. this increases the diameter and length of the cavity which is invaded by Blood vessels. osteoblasts then deposit new bone around the vessels. 2 proteins derived from osteoblasts comprise an effective bone turnover: RANK ligand which activates NFKb, and osteoprotegerin, which protects bone.

Front 4

Summarize the organisms response to hyper and hypocalcemia

Back 4

Hypocalcemia: increased PTH, activation of osteocytes and clasts, decreased renal calcium excretion, increased clearance of phosphate, decrease in PO4 and increase in PTH stimulate kidney to release precursor to vit d, Vit D increases osteoclast number.
Hypercalcemia: decrease in PTH, increase renal Ca secretion, decrease renal phosphate secretion, decrease in PTH and increase in PO4 decreases VitD synthesis.

Front 5

Summarize the organism's response to hypophosphatemia including VitD metabolism, intestinal absorption of calcium, effects on serum calcium, PTH and renal clearance of phosphate

Back 5

Increase in Vit D, Increase in Calcium absorption, Increase in serum Calcium levels, Decreased PTH levels, and decreased renal clearance of phosphate.

Front 6

Describe the impact on an oral load of phosphate on calcium homeostasis

Back 6

hyperphosphatemia results in complex formation with calcium, leading to lower than normal Calcium levels. this triggers the release of PTH to prevent hypocalcemia. PTH increases VitD, renal secretion of phosphate and reabsorption of calcium.

Front 7

Describe the MOA of estradiol on bone

Back 7

Estradiol directly suppresses IL6 production in human osteoblasts. The RANK OPG system is a bone regulatory system through which osteoblasts signal osteoclast production. with estrogen deficiency, RANK increases. with estrogen, osteoprotegerin binds to RANK, preventing this.

Front 8

Describe the role of the kidney in maintaining calcium levels: 1. indicate where in the nephron calcium transport occurs and indicate what factors stimulate and inhibit calcium transport

Back 8

Kidneys excrete the same amount absorbed from the GI tract. PCT:66%of ca, Thick ascending: 25%, DCT:8%, VitD increases ECF calcium. PTH works on all of this with calcitonin

Front 9

Describe handling of phosphate by the kidney.

Back 9

PTH inhibits phosphate reabsorption by inhibiting the NA-phosphate cotransport in the PCT. this causes phosphaturia