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Physio II > Calcium and Phosphate > Flashcards

Calcium and Phosphate Flashcards

1
Q

Calcium and phosphate levels are regulated by PTH and vitamin D via interaction of what 3 target organs?

A

Bone, intestine, kidney

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2
Q

What type of cells in the parathyroid gland release PTH after stimulation by low serum calcium?

A

Chief cells

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3
Q

Cushingnoid syndromes and glucocorticoid therapy lead to an increase or decrease in PTH secretion?

A

Increase

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4
Q

Increased plasma calcium has a negative feedback loop leading to a decrease in Ca and PO4 via what 2 things?

A

Calcitonin release Inhibition of bone resorption and tubular resorption

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5
Q

Does excess calcitonin produce hypocalcemia?

A

No

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6
Q

Does a deficiency in calcitonin lead to dramatic hypercalcemia?

A

No

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7
Q

Once the inactive form of vitamin D enters the body from the diet/ skin, it undergoes 2 steps of activation. Where in the body do these steps occur and what happens?

A

1st activation: addition of OH to carbon 25 in liver 2nd activation: addition of OH to carbon 1 in kidney

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8
Q

What is the active form of vitamin D?

A

1,25- dihydroxycholecalciferol

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9
Q

How does vitamin D act with PTH in the bones, leading to resorption, remodeling, and mobilization of calcium and phosphate?

A

Synergistic

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10
Q

Vitamin D promotes calcium and phosphate reabsorption in what parts of the kidney?

A

Calcium in DCT Phosphate in PCT

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11
Q

Vitamin D increases calcium absorption by the small intestine by increasing expression of what molecule?

A

Calbindin (Calcium crosses apical membrane via diffusion then binds to calbindin to be pumped across basolateral membrane by Ca-ATPase)

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12
Q

What does chronic vitamin D intake lead to?

A

Decreased PTH secretion

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13
Q

Where is the majority of calcium held?

A

99% in crystalline form in teeth and bone (Of remaining 1%- 0.9% in soft tissue and 0.1% in ECF) (Half of portion in ECF is in ionized active form)

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14
Q

What is meant by the fact that calcium is in equilibrium with the bone pool?

A

Amount removed from ECF for bone formation = amount returned to ECF by bone resorption (This favors bone remodeling)

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15
Q

Any amount of calcium absorbed by the GI tract must also be what?

A

Excreted via stool/ urine

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16
Q

What is necessary for metabolic pathways of fuel provision, high energy trasfer/ storage, cofactors, and 2nd messengers?

A

Phosphate

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17
Q

Muscle weakness, cardiac/ respiratory arrest, and loss of RBC integrity results from what?

A

Phosphate depletion

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18
Q

How is phosphate distributed within the body?

A

85% in bones/ teeth, 15% in muscles

(Within cells > 80% in mitochondria)

(Excretion via kidney/ urine > feces)

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19
Q

What area of bone are the following things located?

Stable pool?

Labile pool?

Osteocytic-osteoblastic bone membrane?

A

Stable pool- mineralized bone (superficial layer)

Labile pool- bone fluid

Osteocytic-osteoblastic bone membrane- canaliculi

20
Q

What property of the osteocytic-osteoblastic bone membrane allows for a large influx of Ca between bone fluid and plasma even with a small net movement of Ca?

A

Large SA

21
Q

How does the stable Ca pool contribute to Ca and PO4 release into ECF?

A

Resorption = PTH induced slow breakdown of bone crystal

22
Q

How does the labile Ca pool contribute to Ca and PO4 release into ECF?

A

Osteolytic osteolysis = fast release into ECF

23
Q

What hormone contributes to osteoblast regulation of osteoclast function to increase plasma Ca/ PO4?

A

PTH

24
Q

PTH contributes to increased Ca and PO4 in the blood first by recruitment and differentiation of what type of cells?

A

Stromal cells within stable pool of Ca

25
Q

What do stromal cells differentiate into?

A

Osteoblasts via Runx2 (transcription factor)

26
Q

Once differentiated osteoblasts are targeted by PTH, what 3 things are releaed?

A

Monocyte colony stimulaing factor

RANKL

OPG

27
Q

What is the role of monocyte colony factor?

A

Preosteoclast differentiation

28
Q

What contributes to the clustering and fusion of preosteoclasts to then form a mature osteoclast?

A

RANKL

(Mature osteoclasts then settle on resorption cavity of bone)

29
Q

What is the role of OPG in PTH stimulation of increased plasma Ca/ PO4?

A

Binds to RANK on osteoclasts = bone breakdown (via HCL/ hydrolytic enzymes) = release of Ca and PO4 into blood

30
Q

How does PTH affects the kidney by inhibiting PO4 reabsorption and contributing to the phosphaturic effect?

A

Elimination of PO4 via cAMP

31
Q

How does PTH affect the kidney with respect to activation of vitamin D?

A

Stimulates 1-alpha-hydroylase

32
Q

What disease is defined a mutation in transcription factor Runx2 that leads to abnormal bone formation (clavicles, fontanels, teeth)?

A

Cleidocranial dysplasia

33
Q

“Stones, bones and groans” and complications of osteoporosis, osteomalacia, kidney stones, muscle weakness, and decreased muscle excitability is indicative of what disease?

A

Primary hyperparathyroidism (PTH secreting adenoma)

34
Q

What disease is typically a consequence of thyroid surgery (ex. tx of cancer or Grave’s)?

A

Hypoparathyroidism

35
Q

Complications caused by hypocalcemia and leading to tetany, hyperreflexia, spontaneous twitching, muscle cramps, and convulsions are indicative of what disease?

A

Hypoparathyroidism

36
Q

What disease is described as malignant cells in the breast and lung which secrete PTH related peptide (PTH-rp) that binds to the PTH receptor and has similar actions as PTH?

A

Humoral hypercalcemia of malignancy

37
Q

Albright’s hereditary osteodystrophy is aka?

A

Pseudohypoparathyroidism

38
Q

Pseudohypoparathyroidism is an autosomal disorder with defective what?

A

Gs in kidney and bone

39
Q

Pt who is short, obese, has a short neck, and shortened 4th metatarsals and metacarpals likely has what condition?

A

Pseudohypoparathyroidism

40
Q

A vitamin D deficiency in children vs adults presents as what?

A

Children = Rickets

Adults = osteomalacia

41
Q

In Rickets disease, there is insufficient vitamin D, Ca, and PO4 to mineralize growing bone. What effect will this have on growth?

A

Growth failure and skeletal abnormalities

42
Q

Why do you see hypocalcemia in Rickets disease?

A

Decreased Ca and PO4 absorption in gut (secondary to vit D deficiency)

43
Q

Will a pt with Rickets have elevated or low levels of PTH?

A

Elevated

44
Q

Complications of tetany, muscle weakness, and greenstick fractures are indicative of what condition?

A

Rickets

45
Q

What are the causes of hypocalcemic tetany and hypocalcemia seen with osteomalacia? (4)

A

Dietary deficiency, intestinal surgery, malabsorption, renal failure

(malabsorption can be caused by malabsorption syndrome or Celiac disease)

46
Q

Complications of softened/ weakened bones and frequent fractures are indicative of what condition?

A

Osteomalacia

Physio II (14 decks)

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