Calcium and Phosphate

Question 1

About 50% of Ca is free and

Answer 1

50% is bound to protein

Question 2

Ca is mostly bound to

Answer 2

albumin

Question 3

Chvostek and trousseau sign indicate

Answer 3

hypocalemia, alkalosis, or high albumin (twitching, hyperexcitable)

Question 4

Acidosis

Answer 4

hypercalemia (H+ binds albumin) decreased excitability and muscle weakness

Question 5

Phosphate is the major anion, hypophsophatemia

Answer 5

85% is unbound, cellular ATP production is impaired

Question 6

What modulates phosphate metabolism?

Answer 6

vitamin D3

Question 7

What modulates Mg exchange?

Answer 7

Vitsamin D3 and PTH

Question 8

Amorphous crystals

Answer 8

labile crystals of Calcium phosphate

Question 9

Osteocytic osteolysis

Answer 9

fats exchange of Calcium in the crystals with the ECF compartment (NOT bone resorption)

Question 10

Hydroxyapatite crystals

Answer 10

within the matrix of the bone, slow exchange of Ca

Question 11

BONE resorption

Answer 11

Ca exchange from hydroxyapatite crystals

Question 12

Osteoblasts

Answer 12

surface of bone, secrete alkaline phosphatase to precipitate Ca and produce bone collagen

Question 13

Osteoclasts

Answer 13

multinucleated, precursor cells, dissolve hydrxyapatite by secreting collagenase to degrade the collagen matrix

Question 14

Alkaline phosphatase for _________ and collagenase for _________

Answer 14

bone production; bone resorption

Question 15

Osteocytes

Answer 15

inactive, within matrix, conduit for Ca retrieval from amorphous crystals and delivery of Ca to ECF

Question 16

bone remodeling

Answer 16

osteoblastic and osteoclastic activity for normal bone growth and adaptation to mechanical load

Question 17

Bone remodeling occurs at the

Answer 17

resorption at ENDOSTEAL and deposition at PERIOSTEAL

Question 18

Bone remodeling

Answer 18

quiescence, activation, resorption, reversal, and formation

Question 19

quiescence

Answer 19

osteoblast inactivity

Question 20

activation

Answer 20

osteoblast precursor stimulate collagenase release

Question 21

Resorption

Answer 21

recruitment of osteoclasts and binding to integrins, form ruffled membrane and secrete H+ and enzymes to degrade the collagenase, collagen, and hydroxyapatite

Question 22

Resorption results in

Answer 22

Ca and Po delivery to ECF

Question 23

Reversal

Answer 23

Macrophages appear on resorbing surface

Question 24

Formation

Answer 24

osteoblasts secrete collagen type I and hydroxyapatite crystals mineralize

Question 25

Even though more Ca is contained in the cortical bone (shaft) Ca is replaced more often in the

Answer 25

trabecular bone (ends)

Question 26

PTH production

Answer 26

peptide, chief cells in parathyroid gland

Question 27

PTH secretion

Answer 27

PTH in inverse to [Ca] 3.5-5.5 and vitamin D is permissive

Question 28

Estrogen and testosterone effect on PTH

Answer 28

inhibits PTH

Question 29

What inhibits PTH?

Answer 29

GH, IGF-1, Insulin

Question 30

What activated PTH?

Answer 30

Cortisol, T3 and T4, and

Question 31

The only example where an increase in [Ca] inhibits excretion

Answer 31

PTH

Question 32

Reciprocal relationship between Ca and Po

Answer 32

an increase in PO can impair mobilization of Ca

Question 33

What if you cannot excrete PO due to renal failure?

Answer 33

high levels of PO would result in low levels of Ca due to their reciprocal relationship

Question 34

Vitamin D3

Answer 34

Made in the dermis (isomerized by light waves)

Question 35

Vitamin D3 metabolism

Answer 35

highly regulated hydroxylations

Question 36

Vitamin D3 is activated in response to

Answer 36

low plasma Ca, low PO in plasma, D3 deficiency, or HIGH PTH

Question 37

Vitamine D3 inactivated by

Answer 37

normocalcemia or hypercalemia, normophosphatemia or hyperphosphatemia

Question 38

Vitamin D mechanism

Answer 38

bound to gc-globulin transport acts like steroid hormone with intracellular receptors

Question 39

Vitamin D action

Answer 39

increase Ca and PO, increased absorption, increased resorption

Question 40

Calcitonin secretion

Answer 40

parafollicular cells of thyroid gland

Question 41

Calcitonin mechanism

Answer 41

INHIBIT BONE RESORPTION no evidence of bone formation

Question 42

Hypocalcemia

Answer 42

stimulated PTH, renal resorption of Ca, Ca release from bone, vitamin D3 production, increased intestinal Ca absorption (promote renal excretion of PO)

Question 43

Renal Failure

Answer 43

Hypocalcemia due to inability to excrete PO and low Vitamin D3 which will alter PO and Ca concentrations

Question 44

Hypocalcemia

Answer 44

deficient PTH, deficient VitaminD, renal failure

Question 45

Hypercalcemia

Answer 45

reverse effects by lowering PTH and secreting Calcitonin (decreases resorption)

Question 46

Hypophosphatemia

Answer 46

could be related to hypercalcemia; stimulates Vitamin D3 which will increased both PO and Ca, but hypercalcemia will inhibit PTH decreasing the Ca reabsorption (increased urine excretion of Ca)

Question 47

Aging and its effect on Bone

Answer 47

decreased Vitamin D and decreased Ca and PO absorption from GI

Question 48

Menopause and decreased estrogen

Answer 48

increased sensitivity of bone to PTH INCREASED RESORPTION

Question 49

Immobilization

Answer 49

bone resorption