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𝚙𝚑𝚢𝚜𝚒𝚘𝚕𝚘𝚐𝚢 𝟸 : 𝚖𝚞𝚜𝚌𝚞𝚕𝚘-𝚜𝚔𝚎𝚕𝚎𝚝𝚊𝚕 > The Skeleton And Metabolism > Flashcards

Flashcards in The Skeleton And Metabolism Deck (43)
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1

What are the 6 hormones that have skeletal effects?

→ Estrogens
→ Androgens
→ Cortisol
→ PTH
→ Vitamin D
→ Calcitonin

2

What is a hormone secreted from the skeleton?

→ FGF-23

3

What is the daily calcium intake?

→ 1000-1200

4

How is the calcium distributed in the body?

→ most is intracellular
→ the remaining 0.1% is in the plasma
→ half of the 0.1% is free calcium ions
→ the other half is protein bound

5

What is the only way to increase Ca2+?

→ Increase calcium absorption through the gut

6

What does bone turnover contribute to?

→ Homeostasis of serum calcium
→ phosphate
→ and PTH, vit D, calcitonin, FGF-23

7

What is PTH synthesized from?

→ Parathyroid chief cells

8

Where are the parathyroid glands located?

→ behind the thyroid

9

What is PTH secreted as?

→ 84 AA polypeptide

10

What is the role of PTH?

→ Defend against hypocalcaemia

11

What is the concentration of plasma Ca2+?

→ 2.2-2.6 mM

12

Where is free Calcium sensed?

→ by GPCR on chief cells

13

What is the stimulus for PTH release?

→ Low calcium

14

Where is calcitriol synthesized and in response to what?

→ in the skin
→ in response to UV

15

What is calcitriol?

→ Vitamin D

16

Describe calcitriol synthesis

→ 7dehydrocholesterol is in the skin
→ UV light turns it into cholecalcitriol (CCF)
→ 25 hydroxylase adds an OH group in the liver
→ it becomes 25 hydroxyCCG
→ 1a hydroxylase stimulated by PTH in the kidney adds another OH group
→ 1,25 dihydroxyCCF is formed or calcitriol

17

Where is the regulation site for calcitriol?

→ control of 1a hydroxylase in the kidney

18

What is calcitriol increased by?

→ PTH - upregulates 1a hydroxylase
→ Low phosphate

19

What is the function of calcitriol?

→ Increase absorption of Ca and Pi from the GI tract
→ inhibits PTH

20

What are the 4 actions of PTH?

→ Promotes release of Ca from bone
→ Increases Ca reabsorption
→ increases renal Pi excretion
→ upregulates 1a hydroxylase activity

21

Describe how PTH works

→ hypocalcaemia stimulates PTH
→ PTH binds to osteoblasts and stimulates RANK ligand
→ RANK ligand binds to RANK receptors on osteoclasts
→ Bone breaks down and Ca2+ and phosphate are released into the blood

22

Where are PTH receptors found?

→ osteoblasts

23

How does PTH promote bone remodelling?

→ Activates osteoclasts via RANKL
→ promotes bone remodelling

24

What does intermittent low dosage of PTH lead to?

→ favoring formation over reabsorption

25

What does a persistent high concentration of PTH lead to?

→ excess resorption over formation

26

Where is calcitonin secreted from?

→ C cells of the thyroid

27

What stimulates calcitonin secretion?

→ high Ca2+

28

What is the effect of calcitonin?

→ to lower Ca2+ by inhibiting osteoclasts

29

What does calcitonin do in the kidney?

→ Decreases calcium and phosphate reabsorption

30

What does calcitonin do in the bone?

→ Decreases bone resorption by inhibiting osteoclast activity