15. Bone Ossification

Question 1

4 types of cells

Answer 1

Osteopeogenitor (stem)
Osteoblasts (secrete osteoid)
Osteocytes (Osteoblasts trapped in unmineralised bone)
Osteoclasts (destroy)

Question 2

What does the Extracellular matrix contain?

Answer 2

Collagen
Calcium (+phosphate) hydroxyapatite

Question 3

What is osteoid

Answer 3

Unmineralised bone:
Type 1 collagen
Proteoglycans
Glycosaminoglycans

Mineralises when there’s high Ca2+, K+

Question 4

Why are there small canaliculi between osteocytes?

Answer 4

For oxygen and nutrients

Question 5

Describe osteoclasts structure

Answer 5

Large multinucleate cells derived from monocytes. Absorbs bone by forming depressions called Howships’s lacunae to remodell and meet structural demands,

Question 6

What regulates activity of osteoblasts and osteoclasts?

Answer 6

Rank-ligands

Question 7

Types of bone

Answer 7

Primary = woven = Layed down rapidly so disorganised collagen is weak

Secondary = Lamellar = stronger and forms osteons

Question 8

What are osteons?

Answer 8

Concentring rings of lamellar bone with osteocytes surrounding a central Haversian canal of blood vessels

Question 9

Types of bone formation

Answer 9

Intramembranous = flag + corticol bone = osteoblasts form woven

Endochondrial = all other bones = proforma cartilage erodes and secondary centres remodel to produce lamellar bone

Question 10

Describe synovium joint structure

Answer 10

Lined by hyaline cartilage and joint capsule.
Inner specialised synovial cells have 1-4 layers.
Variable shoes (squamous to cuboidal) with rich vascular supply and innervation.

Question 11

Type A vs B synovial cells

Answer 11

A - phagocytes
B - rich in rER and secrete synovial fluid

Question 12

Corticol vs cancellous bone

Answer 12

Co - end of bone formed from osteons
Ca - shaft of bone formed from trabeculae