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Skeletal Physiology: Bone Health > Lecture 1 > Flashcards

Flashcards in Lecture 1 Deck (34):
1

What is Bone made up of

Type 1 Collagen

2

What is Bone filled with

Hydroxyapatite

3

Calcium management

Skeleton acts as a reservoir for Ca

4

Types of hormones which offer skeletal management

Sex Steroid, thyroxine, corticosteroids and insulin

5

4 cell types relevant to bone formation and metabolism

Osteoblasts, Osteoclasts, Osteocytes, Osteoprogenitor

6

Osteoblasts position

Bone Surface

7

Osteoblasts Feature

Responsible for laying down bone

8

Osteoclasts Position

Bone surface but low numbers

9

Osteoclasts Features

Move across bone surface reabsorbing bone, multinucleated and contain many mitochondria

10

Osteocytes Position

Cannot divide, most abundant cell in bone, networked by canaliculi

11

Osteocytes Features

Cannot divide, most abundant cell in bone. Networked by canaliculi

12

Three Hormones that play vital roles

Calcitrol, Parathyroid Hormone, Calcitonin

13

Calcitrol

Active form of Vitamin D

14

Role of Calcitrol

Increases blood Ca2+

15

How does Calcitriol increase Ca2+

Increase calcium and phosphate absorption from Intestines
Increasing calcium resorption from bone via indirect osteoclast and direct osteoblast stimulation, decreasing urinary excretion of calcium, by increasing calcium reabsorption by kidneys.

16

How does calcitriol act

Bids to nuclear receptor protein on target tissue and regulate gene expression

17

Parathyroid Hormone role

Increase calcium resorption from bone via indirect osteoclast stimulation
Decreasing urinary excretion of calcium, by increasing calcium resorption by kidneys
Increasing urinary excretion of inorganic phosphate, by decreasing Pi reabsorption by kidneys
Stimulating calcitriol production in the kidneys

18

Role of Calcitonin

Decreases blood Ca2+

19

How does Calcitonin decrease Ca2+

Inhibiting calcium resorption from bone via direct osteoblast stimulation
Increasing urinary excretion of calcium and inorganic phosphate by decreasing resorption by kidneys.

20

Bone Mineral Density

g bone mineral per cm^2

21

Peak Bone Mass

The amount of bony tissue present at the end of the skeletal maturation

22

Lower BMD=

Greater chance/ severity of fracture

23

Bone Density decreases Over time

Oestrogen inhibits bone resorption by reducing osteoblast numbers and activity. A lack if oestrogen allows osteoclast to be more active allowing bone resorption to occur.

24

Osteoporosis

BMD lies 2.5 standard deviations or more below the average value for young healthy person (T- score)

25

Osteopenia

T- Score between -1 to -2.5

26

Typical stress points

Spine, Hip and wrist

27

Why are women more at risk

Menopausal effect (Oestrogen)
Affected by previous pregnancies
Women tend to live longer

28

Osteomalacia

softening of the bones, typically through a deficiency of vitamin D or calcium.

29

Mothers at risk due to

- Low Ca intake
-Low sun exposure
-Long periods of lactation

30

Role of Vitamin D3

Bone growth, Cells of the immune system, pancreas, skin

31

Causes in VD deficiency

Poor diet, inability to absorb/ metabolise vitamin D3, low sunlight exposure

32

Vitamin D3 Formation

1. Sunlight (UV), shining on the skin
2. Inactive form of VD travels to the liver and then the kidneys in a 2 step activation pathway.
3. Active VD can then enter cells and stimulate receptor protein to bind to DNA in the nucleus, acting as a regulator for hundreds of genes.

33

How is VD3 deficiency a risk factor

Risk factor for osteoporosis and osteomalacia

34

Why is sufficient Calcium vital for achieving a high peak bone mass

Peak total body BMD and BMC is attained by the age of 22 yrs and 26 yrs
During adolescence around 50 % of peak bone mass is laid down