LG 2.3 Physiology of Bone

Question 1

1. What type of cell is this? What is it’s function? (3)

Answer 1

1. Osteoblast. “builds” bone

Question 2

2. What type of cell is this? What is its function? (3)

Answer 2

2. Osteoclast. function = bone resorption

Question 3

3. What type of cell is this? (3)

Answer 3

3. Osteocyte –> mature bone cell that monitors and maintains the mineralized bone matrix

Question 4

4. What hormone stimulates osteoblasts to secrete cytokines? (3)

Answer 4

Parathyroid Hormone

Question 5

5. What cytokines do osteoblasts secrete that stimulate osteoclast activity? (3)

Answer 5

5. RANK-ligand and M-CSF

Question 6

1. What stimulates PTH release? (5)

Answer 6

low blood Ca2+ levels

Question 7

2. What does PTH effect at the level of bone? (5)

Answer 7

PTH binds to osteoblasts and simulates them to release cytokines, like RANK-ligand and M-CSF. These cytokines bind receptors on Osteoclast cells, which activates bone resorption function of osteoclasts –> RAISES blood Ca2+ levels

Question 8

3. What does PTH do at the kidneys? (5)

Answer 8

PTH stimulates Ca2+ reabsorption from the kidneys (also causes phosphate excretion at the kidneys). PTH acts on kidneys to convert vitamin D to active Vitamin D

Question 9

4. What does active vitamin D do at the bone level? (5)

Answer 9

Vitamin D acts on bones to increase bone resorption (stimulates osteoclast/osteoblast interaction)

Question 10

5. What does active vitamin D do in the intestines?

Answer 10

increases Ca2+ absorption in the small intestine

Question 11

1. What stimulates calcitonin secretion? (6)

Answer 11

High levels of Ca2+ in the blood. Calcitonin works to decrease blood Ca2+ levels

Question 12

2. What does calcitonin do at the level of bone? (6)

Answer 12

Inhibits bone resorption activity of osteoclasts (so less Ca2+ secreted into the blood)

Question 13

3. What does calcitonin do in the kidneys? (6)

Answer 13

Inhibits Ca2+ reabsorption in the kidneys (so increased secretion