parathyroid anatomy and physiology

Question 1

what hormone is released from the parathyroid?

Answer 1

parathyroid hormone

Question 2

3 main roles of parathyroid hormone

Answer 2

• increase bone resorption (breakdown) - increase cytokine release from osteoblasts - stimulate osteoclasts
• increase kidney reabsorption of calcium to keep it in the blood and potassium excretion
• vitamin D synthesis - this in turn stimulates calcium absorption from the gut

Question 3

What effect does PTH have on calcium and phosphate absorption?

Answer 3

Increases Ca reabsorption by the distal renal tubule
PTH decreases phosphate reabsorption by the proximal renal tubule

Question 4

What is PTH action pathway?

Answer 4

PTH acts on the target cell (bone, kidney)
Uses secondary mesengers, such as cyclic AMP and calcium

Question 5

How does parathyroid hormone affect phosphate?

Answer 5

Increases 1,25 vitamin D causing increased active gut absorption
Decreases tubular reabsorption of phosphate causing renal excretion

Question 6

what hormones moderate bone growth and breakdown?

Answer 6

calcitonin - growth
PTH - breakdown

Question 7

name the bone cells and their roles

Answer 7

osteoblasts - bone formation by synthesising and secreting bone matrix

osteocytes - Mature bone cells that maintain bone tissue, regulate mineral content, and communicate with other bone cells to coordinate bone remodeling

osteoclasts - bone resorption

Question 8

how is PTH regulated and controlled?

Answer 8

blood calcium levels
- low levels - PTH released
- high levels PTH inhibited

CaSRs in parathyroid sense blood Ca level

Question 9

name some roles of calcium

Answer 9

• bone strength
• muscle contraction - binds to troponin
• nerve transmission - neurotransmitter release at synapse
• blood clotting - coag cascade

Question 10

role of vitD in bone maintanance

Answer 10

• increases ca absorption from the intestines
• promotes ca reabsorption in kidneys