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Locomotor > Physiology of Bone & Calcium Homeostasis > Flashcards

Physiology of Bone & Calcium Homeostasis Flashcards

1
Q

3 main hormonal controllers of Ca+2

A 
Parathyroid Hormone (PTH)
Vitamin D3 (calcitrol)
Calcitonin
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2
Q

main hormones involved in growth

A

Growth Hormone and IGFs
Thyroid hormone (permissive role in growth, direct contribution for nervous system development)
Insulin
Sex Steroid

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3
Q

main histological constituents of bone

A

Cells (osteoclasts, osteoblasts, osteocytes, osteoprogenitor cells)
Extracellular Matrix (Collagen, Calcium Phosphate)
[most common Hydroxyapatite]

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4
Q

main constituents of bone macroscopically

A

Cortical bone
Trabecular Bone
Bone Marrow

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5
Q

Main cell type on which bone growth depends

A

Osteoblasts

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6
Q

main product of the osteoblast

A

Enzymes + Osteoid [collagen+protein mix]

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7
Q

main site of bone growth

A

epiphyseal plate

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8
Q

3 main divisions of bone

A

epiphysis
metaphysis
diaphysis

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9
Q

where in the bone are the chondrocytes localised

A

epiphysis

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10
Q

once they have laid down the osteoid osteoblasts become

A

osteocytes

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11
Q

osteoclasts are

A

large, mobile, multinucleate cells

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12
Q

osteoclasts and osteoblast are derived from the same cell lineage

A

F.
osteoclasts are derived from Haematopoietic Stem Cells
osteoblasts mesenchymal stem cells

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13
Q

what are the main products of osteoclasts

A

acid and proteases

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14
Q

name some of the functions of calcium

A

intracellular signal
structural functions (cement of the tight junction)
cofactor in blood coagulation
normal excitability of neurone and muscle

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15
Q

what are the main 3 pools of calcium within the body

A 
bone matrix (99%)
extracellular (0.1%)
intracellular (0.9%)
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16
Q

what are the main target sites for calcium regulation

A

small intestine
bone
Kidney

17
Q

how much of Daily calcium intake is absorbed by the intestine?

A

1/3

18
Q

main regulators of calcium uptake from the intestine

A

PTH

Calcitrol

19
Q

how is most calcium lost in the body

A

via urine

20
Q

what is the main signal for the release of parathyroid hormone PTH? what type of hormone is it?

A 
low plasma (extracellular) calcium
peptic hormone, little stored
21
Q

main results after the release of PTH?

A

increasing plasma calcium and decreasing plasma phosphate levels

22
Q

actions of PTH on bone are by directly stimulating osteoclasts

A

F
osteoclast do not have receptors for PTH. PTH actions are mediated by binding to osteoblasts and inhibiting the production of osteoprotegin (OPG) and increasing RANKL

23
Q

where is the parathyroid?

A

4 small glands that sit behind the thyroid

24
Q

in order of time, what are the main results PTH at different targets?

A

Kidneys min
Bone hours
Intestine days

25
Q

what is the main function of PTH on the intestine?

A

indirectly increases ca+2 absorption by increasing the synthesis of calcitrol

26
Q

what is the main function of PTH on the kidneys?

A

increase reabsorption of calcium and decrease reabsorption of phosphate

27
Q

where is the main site for calcitonin secretion?

A

C cells of the thyroid

28
Q

what is the main stimulus for the release of calcitonin?

A

high Ca+2 levels

29
Q

actions of calcitonin

A

lowering plasma calcium and phosphate

30
Q

just as PTH calcitonin has a homeostatic role

A

F, only secreted in extreme hypercalcaemia

may have a role protecting the bone during lactation and pregnancy

31
Q

main target sites and functions of calcitonin?

A

kidney increase excretion of both calcium and phosphate

increase bone deposition

32
Q

what is the main vitamin D precursor obtained from the diet and also produced in the body when exposed to direct sunlight?

A

Vitamin D3 (17-dehydrocholesterol)

33
Q

in order to obtain the active form of vitamin D, calcitrol, adding of 2 hydroxyl groups are required this is done sequentially in —1—- and —2— being the site of action of PTH

A

Liver

Kidney

34
Q

Vitamin D travels bound to plasma proteins? and what is the name of the main active form?

A

T

1.25-Dihydroxycholecalciferol –> Vitamin D3 —> calcitriol

35
Q

what are the main outcomes of vitamin D deficiency?

A

Children –> rickets

Adults –> osteomalacia

36
Q

main function of oestrogen in bone?

A

increases deposition of bone and

decreases reabsorption

37
Q

risk factors for osteoporosis?

A 
female 
>50
smoker
alcohol intake 
vegan 
immobility

Locomotor (20 decks)

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