L19+20: Calcium and Phosphate

Question 1

most calcium is

Answer 1

found in crystalline form in bone

Question 2

net daily absorption/excretion of calcium

Answer 2

200 mg

Question 3

free+bound calcium in blood

Answer 3

10 mg

half free, half bound

Question 4

net daily absorption/excretion of phosphate

Answer 4

650 mg

Question 5

Most phosphate is found in

Answer 5

bones (85%)

muscle (15%)

Question 6

Phosphate functions

Answer 6

1. fuel provision, high energy transfer/storage
2. cofactors (NAD)
3. second messengers

Question 7

regulate calcium and phosphate levels in blod

Answer 7

PTH

vitamin D

Question 8

trigger for PTH release

Answer 8

hypocalcium

Question 9

PTH is released from

Answer 9

chief cells of parathyroid glands

Question 10

PTH effects on bone:

Answer 10

activates osteoclasts: bone breakdown: calcium and phosphate ions released into blood

Question 11

PTH effects on intestine:

Answer 11

increased calcium absorption

Question 12

PTH effects on kidney:

Answer 12

1. promotes activation of vitamin D
2. increases calcium reabsorption
3. promotes excretion of phosphate

Question 13

mineralized bone

Answer 13

hydroxyapatite: Ca10(PO4)6(OH)2

Question 14

stable pool

Answer 14

slow resorption, contains mineralized bone

Question 15

Labile pool

Answer 15

fast osteolytic osteolysis, contains bone fluid of amorphous crystals

Question 16

amorphous crystals

Answer 16

CaHPO4:2H2O

Question 17

separates the bone from plasma within canals

Answer 17

osteocytic-osteoblastic bone membrane

-formed by projection from osteocytes

Question 18

osteocytic-osteoblastic bone membrane function

Answer 18

large surface area: small movement of calcium across the membrane=large influx between bone fluid and plasma

Question 19

what moves calcium across the osteocytic-osteoblastic bone membrane

Answer 19

fast exchange: PTH-activated calcium pumps

slow exchange: PTH-induced dissolution of bone

Question 20

elimination of PO4 in urine leads to increased

Answer 20

urine cAMP

Question 21

how does PTH activate vitamin D

Answer 21

stimulates 1-alpha hydroxylase activity

Question 22

sunlight converts

Answer 22

7-dehydrocholesterol to vitamin D3

Question 23

vitamin D3 activation

Answer 23

Liver:
adds OH to C25
25-hydroxyvitamin D3

Question 24

25-hydroxyvitamin D3 activation

Answer 24

Kidney:
add OH to C1
1,25-dihydroxyvitamin D3

Question 25

25-hydroxyvitamin D3 inactivation

Answer 25

add OH to C24 | 24,25-dihydroxyvitamin D3

Question 26

active form of vitamin D

Answer 26

1,25-dihydroxyvitamin D3

Question 27

vitamin D action on bone

Answer 27

synergistic with PTH | resorption: mobilization of calcium and phosphate

Question 28

vitamin D action on kidenys

Answer 28

promotes calcium reabsorption at distal tubule | promotes phosphate reabsorption at proximal tubule

Question 29

vitamin D action on small intestine

Answer 29

increases expression of calbinding

Question 30

calbindin

Answer 30

in small intestine cells | binds calcium, which is then pumped into bloodstream by Ca-ATPase on basolateral membrane

Question 31

stimulus for calcitonin release

Answer 31

high plasma calcium

Question 32

Calcitonin actions

Answer 32

1. inhibits bone resorption of Ca and PO4 | 2. inhibits renal reabsorption of Ca and PO4

Question 33

Calcitonin effect on intestines

Answer 33

none

Question 34

Primary hyperparathyroidism

Answer 34

causes by PTH-secreting adenoma 1. hypercalcemia, hypophosphatemia 2. urine: increased PO4, cAMP, hypercalciuria osteorporosis, osteomalacia, kidney stones, muscle weakness and decresed muscle excitability

Question 35

Hypoparathyroidism

Answer 35

caused by surgery Low PTH, hypocalcemia, hyperphosphatemia Hypocalcemia: teatany, hyperreflexia, spontaneous twitching, muscle cramps, convulsions

Question 36

Positive trousseau's sign

Answer 36

flexed hand? | due to low calcium levels in hypoparathyroidism

Question 37

Humoral hypercalcemia of malignancy

Answer 37

PTH-related peptide (PTH-rp) secreted effects of excess PTH PTH levels are low due to hypercalcemia

Question 38

Pseudohypoparathyroidism aka

Answer 38

albright's hereditary osteodystrophy

Question 39

Pseudohypoparathyroidism

Answer 39

autosomal dominant disorder Defective Gs is PTH resistant Elevated PTH, hypocalcemia, hyperphosphatemia Short, short neck, obese, shortened metatarsals and metacarpals

Question 40

vitamin D deficiency in childhood

Answer 40

rickets

Question 41

vitamin D deficiency in adulthoood

Answer 41

osteomalacia | usually dietary deficiency or intestinal surgery, renal failure, celiac disease

Question 42

Rickets

Answer 42

insufficient vitamin D to mineralize growing bone growth failure, skeletal abnormalities, tetany, weakness, fractures hypocalcemia elevated PTH

Question 43

Osteomalacia

Answer 43

softened, weakened bones, frequent fractues | hypocalcemia, tetany