BONE BIOLOGY

Question 1

hierarchy of bone

Answer 1

mineralised collagen fibrile –> fibre arrays –> secondary osteons –> whole bone

Question 2

cortical/compact bone structure

Answer 2

1. osteons
2. concentric lamellae containing haversian canals where blood vessels sit
3. lacunae where osteons sit
4. canaliculi –> channels between lacunae used for communication between osteocytes
5. volkmann’s canals contain trnasverse blood vessels

Question 3

Bone content

Answer 3

Organic components - collagen 1, fibrous proteins and GAGs - provide tensile strength
Mineral components - compressive strength, HA

Question 4

osteocytes

Answer 4

sit in bone matrix, in charge of maintaining bone and communicating with canaliculi. Several years lifespan

Question 5

osteoblast

Answer 5

bone building cells, lifespan around 100 days, lay down new bone material, make collagen fibres and PGs, can become osteocytes over time if they get stuck in the bone matrix.

Question 6

osteoclasts

Answer 6

Bone destroying cells, very short life spans a matter of 12 days, remove bone - secrete H+ to dissolve minerals and collagenase to remove protein, Multinucleated (larger than osteoblasts)

Question 7

bone types

Answer 7

flat, long, short, irregular

Question 8

bone functions

Answer 8

support, protection of internal organs, storage of calcium, produces cells, attachment points for muscles.

Question 9

bone cell collaboration for bone turnover

Answer 9

injury,
bone lining recruits osteoclasts
osteoclasts resorb bone creating a resorption pit.
osteoclasts die (apoptosis)
osteoblasts fill pit with osteoid
mineralisation of matrix
maturation of matrix

Question 10

terminology: parts of bone

Answer 10

epiphysis
diaphysis
metaphysis - growth plate
periosteum - outer surface lining
endosteum - inner surface lining
medullar canal - central space containing marrow etc.

Question 11

trabecular bone structure

Answer 11

50-90% porous
rod like structure, found in epiphysis and metaphysis of long bone