skeletal system

Question 1

4 main functions of skeletal system

Answer 1

mechanical - support attachment muscles, ligaments, tendons

protective - internal organs

haematopoiesis - blood cell formation

metabolic - reserves of calcium and phosphate

Question 2

2 types of bone

Answer 2

trabecular bone (inner)

cortical/ compact bone

Question 3

what are bones made up of (3)

Answer 3

water

protein (collagen type 1 fibres, growth factors, matrix proteins)

minerals (mineralised with hydroxyapatite)

Question 4

chemical formula of hydroxyapatite

Answer 4

Ca10(PO4)6(OH)2

Question 5

what % of bones does water make up

Answer 5

20%

Question 6

what % of bones do proteins make up

Answer 6

35%

Question 7

what % of bones do minerals make up

Answer 7

45%

Question 8

what is the role of hydroxyapatite

Answer 8

makes bones rigid, allows collagen to be stronger in bones than skin

Question 9

3 cells bones are connected with

Answer 9

osteoclasts
ostoblasts
osteocytes

Question 10

how are osteoclasts formed

Answer 10

mononucleated precursor cells

fuse together

multi-nucleated osteoclast progenitor cell

mature

active osteoclasts

Question 11

function of osteoclasts

Answer 11

break down/ remove bone

Question 12

function of osteoblasts

Answer 12

synthesise new bone by laying down collagen fibres

fibres then mineralised by hydroxyapatite - stronger

Question 13

where are osteoblasts located

Answer 13

bone surface

Question 14

where are osteoclasts located

Answer 14

bone surface

Question 15

where are osteocyte cell bodies located

Answer 15

in bone cavity called lacuna

Question 16

where are osteocyte projections located

Answer 16

tunnels in bone called canaliculi

Question 17

function of osteocyte projections

Answer 17

communication throughout bone

Question 18

where do osteocytes originate from

Answer 18

osteoblasts trapped in the bone

Question 19

evidence suggests ___ release collagen fibres so may have a role in building bone

Answer 19

osteocytes

Question 20

bones have ____/____ due to load/ mechanical stress so require constant repair

Answer 20

micro-breaks/ micro-fractures

microfractures damage osteocyte projections, osteocytes release signals to osteoclasts and osteoblasts to begin bone remodelling

Question 21

what is the bone remodelling cycle (4 steps)

Answer 21

quiescence - aka bone lining cells (inactive)

when active, reabsorption (cells recruit osteoclast to remove damaged portion of bone)

reversal (osteoblasts recruited, lay down new collagen fibres to replace bone)

formation (osteoblasts) - mineralisation
returns to quiescence again

Question 22

___ must be equal to ___ for healthy bones

Answer 22

bone loss/ reabsorption

bone gain/ synthesis

Question 23

what is bone reabsorption

Answer 23

removal of bone tissue

Question 24

how does bone reabsorption occur (osteoclast function)

Answer 24

osteoclast breaks down hydroxyapatate/ tissue in bones, release minerals

calcium transferred from bone to blood

can be used elsewhere in the body

Question 25

men lose bone density more rapidly than women with age - true or false

Answer 25

false - post menopause dec. oestrogen production
oestrogen blocks ostoclasts
dec blocking, inc bone breakdown potentially leading to osteoporosis

Question 26

post menopause there is a dec. in oestrogen production which impacts osteoclasts. how and why

Answer 26

oestrogen inhibits maturation of osteoclast progenitor cells into mature ostoclasts that reabsorb bone

Question 27

RECHECKhow is bone remodelling induced

Answer 27

microfractures damage osteocyte projections, osteocytes release signals to osteoclasts and osteoblasts to begin bone remodelling

Question 28

extensive bone remodelling can cause

Answer 28

hypercalciumia

Question 29

in bone reabsorption, calcium transferred from bone to blood, can be used elsewhere in the body. example of use

Answer 29

pregnancy, female bone density dec
as activated osteoclasts to break down skeletal structure and release calcium for developing embryo

Question 30

post menopause dec. oestrogen production
oestrogen blocks ostoclasts
dec blocking, inc bone breakdown potentially leading to osteoporosis. treatment?

Answer 30

HRT - admin exog oestrogen

Question 31

what is an osteoclast progenitor cell

Answer 31

multiple mononucleated cells formed into a multinucleated progenitor cell (not yet mature- no ruffle border)

eventually matures over time for bone reabsorption

Question 32

hetereotopic assification (HO)

Answer 32

bone formation in wrong place

Question 33

what causes hetereotopic assification disease

Answer 33

single point missence mutation of activin A receptor type 1 (ACVR1)
(AA R for H at 206 in GS domain)

Question 34

activin A receptor type 1 (ACVR1)

Answer 34

mediator of bone morphogenic proteins

Question 35

osteoclerosis

Answer 35

abnormal hardening of bone, inc bone density - overactivation of osteoblasts

Question 36

is autosomal dominant osteopetrosis hereditary or acquired

Answer 36

hereditary

Question 37

is malignant infantile osteopetrosis hereditary or acquired

Answer 37

hereditary

Question 38

is osteopoikilosis hereditary or acquired

Answer 38

hereditary

Question 39

is paget’s disease hereditary or acquired

Answer 39

acquired

Question 40

is osteogenic bone metastasis by carcinoma hereditary or acquired

Answer 40

acquired

Question 41

is hypervitaminosis D hereditary or acquired

Answer 41

acquired

Question 42

how common is pagets disease

Answer 42

1-3% in older than 45-55
10% in older than 80

Question 43

osteoporosis

Answer 43

reduction in bone density due to inc bone reabsorption - more fragile

inc osteoclast activity

more common in women