Physiology of Bone & Calcium Homeostasis Flashcards Preview

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Flashcards in Physiology of Bone & Calcium Homeostasis Deck (37):
1

3 main hormonal controllers of Ca+2

Parathyroid Hormone (PTH)
Vitamin D3 (calcitrol)
Calcitonin

2

main hormones involved in growth

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

3

main histological constituents of bone

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

4

main constituents of bone macroscopically

Cortical bone
Trabecular Bone
Bone Marrow

5

Main cell type on which bone growth depends

Osteoblasts

6

main product of the osteoblast

Enzymes + Osteoid [collagen+protein mix]

7

main site of bone growth

epiphyseal plate

8

3 main divisions of bone

epiphysis
metaphysis
diaphysis

9

where in the bone are the chondrocytes localised

epiphysis

10

once they have laid down the osteoid osteoblasts become

osteocytes

11

osteoclasts are

large, mobile, multinucleate cells

12

osteoclasts and osteoblast are derived from the same cell lineage

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

13

what are the main products of osteoclasts

acid and proteases

14

name some of the functions of calcium

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

15

what are the main 3 pools of calcium within the body

bone matrix (99%)
extracellular (0.1%)
intracellular (0.9%)

16

what are the main target sites for calcium regulation

small intestine
bone
Kidney

17

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

1/3

18

main regulators of calcium uptake from the intestine

PTH
Calcitrol

19

how is most calcium lost in the body

via urine

20

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

low plasma (extracellular) calcium
peptic hormone, little stored

21

main results after the release of PTH?

increasing plasma calcium and decreasing plasma phosphate levels

22

actions of PTH on bone are by directly stimulating osteoclasts

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

where is the parathyroid?

4 small glands that sit behind the thyroid

24

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

Kidneys min
Bone hours
Intestine days

25

what is the main function of PTH on the intestine?

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

26

what is the main function of PTH on the kidneys?

increase reabsorption of calcium and decrease reabsorption of phosphate

27

where is the main site for calcitonin secretion?

C cells of the thyroid

28

what is the main stimulus for the release of calcitonin?

high Ca+2 levels

29

actions of calcitonin

lowering plasma calcium and phosphate

30

just as PTH calcitonin has a homeostatic role

F, only secreted in extreme hypercalcaemia
may have a role protecting the bone during lactation and pregnancy

31

main target sites and functions of calcitonin?

kidney increase excretion of both calcium and phosphate
increase bone deposition

32

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

Vitamin D3 (17-dehydrocholesterol)

33

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

Liver
Kidney

34

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

T
1.25-Dihydroxycholecalciferol --> Vitamin D3 ---> calcitriol

35

what are the main outcomes of vitamin D deficiency?

Children --> rickets
Adults --> osteomalacia

36

main function of oestrogen in bone?

increases deposition of bone and
decreases reabsorption

37

risk factors for osteoporosis?

female
>50
smoker
alcohol intake
vegan
immobility