Calcium homeostasis
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kidney. bone. calcium deposition. calcium resorption. 1000 g Ca++ stored in bone. Ca++ absorbed into blood. Ca++ lost in urine. Calcium in the diet. calcium lost in feces. small intestine. Calcium homeostasis. Blood Ca++. storage. kidney. calcium deposition. calcium resorption.

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Calcium homeostasis

kidney

bone

calcium deposition

calcium resorption

1000 g Ca++ stored in bone

Ca++ absorbed into blood

Ca++

lost in urine

Calcium in the diet

calcium lost in feces

small intestine

Calcium homeostasis

Blood

Ca++


storage

kidney

calcium deposition

calcium resorption

intake

Ca++ absorbed into blood

Ca++

lost in urine

excretion

Calcium in the diet

calcium lost in feces

small intestine

Calcium homeostasis

bone

Blood

Ca++

1000 g Ca++ stored in bone


Calcium cycling in bone tissue
Calcium cycling in bone tissue

  • Bone formation

    • Osteoblasts

      • Synthesize a collagen matrix that holds Calcium Phospate in crystallized form

      • Once surrounded by bone, become osteocyte

  • Bone resorption

    • Osteoclasts

      • Change local pH, causing Ca++ and phosphate to dissolve from crystals into extracellular fluids


kidney

bone

calcium deposition

calcium resorption

Ca++ absorbed into blood

Ca++

lost in urine

Calcium in the diet

calcium lost in feces

small intestine

Calcium homeostasis

Blood

Ca++


Hormonal regulators
Hormonal Regulators

  • Calcitonin (CT)

  • Parathormone (PTH)

  • 1,25 Vitamin D3


Calcitonin ct
Calcitonin (CT)

  • Secreted from the C cells in the thyroid

  • Lowers Ca++ in blood

  • Promotes deposition of Ca++ into bone (inhibits osteoclasts)

  • Control of secretion from c-cells:

CT


Hormonal regulators1
Hormonal Regulators

  • Calcitonin (CT)

    • Lowers Ca++ in the blood

    • Inhibits osteoclasts

  • Parathormone (PTH)

  • 1,25 Vitamin D3


Parathormone pth
Parathormone (PTH)

  • Increases Ca++ in blood

  • Increases Ca++ resorption from the bone

    • Stimulates osteoclasts

    • Increases number of osteoclasts

  • Increases Ca++ resorption from nephron

  • Control of secretion:

  • Necessary for fine control of Ca++ plasma levels


Hormonal regulators2
Hormonal Regulators

  • Calcitonin (CT)

    • Lowers Ca++ in the blood

    • Inhibits osteoclasts

  • Parathormone (PTH)

    • Increases Ca++ in the blood

    • Stimulates osteoclasts

  • 1,25 Vitamin D3


1 25 vitamin d3

UV

Cholesterol precursor

7-dehydrocholesterol

Vitamin D3

25 Vitamin D3

1,25 Vitamin D3

Low plasma Ca++ increase kidney enzymes

1,25 Vitamin D3

  • Increases Ca++ uptake from the gut

    • Increase transcription and translation of Ca++ transport proteins in gut epithelium

  • Minor roll: also stimulates osteoclasts

    • Increase Ca++ resorption from the bone


Hormonal regulators3
Hormonal Regulators

  • Calcitonin (CT)

    • Lowers Ca++ in the blood

    • Inhibits osteoclasts

  • Parathormone (PTH)

    • Increases Ca++ in the blood

    • Stimulates osteoclasts

  • 1,25 Vitamin D3

    • Increases Ca++ in the blood

    • Increase Ca++ uptake from the gut

    • Stimulates osteoclasts


kidney

bone

1,25 Vit. D3 (+)

Parathormone (+)

PTH

Ca++

Ca++

1,25 Vit D3

Ca++

Ca++

small intestine

Calcium homeostasis

Blood

Ca++

Calcitonin (-)

resorption

deposition


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