Bone: structure and function Flashcards
1
Q
Define ‘compact bone’
A
- Bone made of Haversian canal
- Mostly mineralized tissue
- highly ordered
- No bone marrow
- Outer layer of all bone structures
- Resistant to bending and breaking
2
Q
Define ‘cancellous bone’
A
- Just layers of bone but less structured (no Haversian canal
- Bone marrow and mineralized tissue
- Trabeculae = struts in bone
- inner layer of bone structures
- Vulnerable to fracture
3
Q
List the types of bone and their distribution throughout the skeleton
A
Compact bone:
- Limbs
- skull
Cancellous bone:
- Vertebrae
- Ribs
4
Q
Describe the composition of bone matrix
A
Compositions of bones: Proteins: - Collagen (type 1): gives bone tensile strength - Non-collagenous proteins: 1) alkaline phosphatase 2) Proteoglycans 3) growth factors
Mineral:
- Hydroxyapatite = crystal of calcium and phosphate
- Gives bone compressive strength
5
Q
Describe osteoblasts
A
- Bone forming cells
- Round
- Synthesize bone matrix
- Mineralized matrix
6
Q
Define ‘lining cells’
A
- flattened osteoblasts
- Line bone surfaces
7
Q
Define ‘osteocytes’
A
- Embedded in bone matrix
- Connect to each other via canaliculae
- sense mechanical forces
8
Q
Define ‘osteoclasts’
A
- Bone resorbing cells
- Multinucleated giant cells (derived from monocytes)
- Dissolve mineral and degrade protein
- Release embedded growth factors from bone (ensure osteoclastic and osteoblastic activity matches)
9
Q
Why does bone turnover?
A
- Shape changes in bone
- Change in bone loading
- Repairing microdamage
10
Q
Describe osteoblast and osteoclast activity
A
Coupled activity -> bone formation and remodelling are balanced.
Growth factors are embedded in bone:
- Osteoclastic activity causes release of GF
- GF causes osteoblast differentiation
RANK-RANKL Binding
- Osteoblasts have RANKL on surface
- RANKL binds with RANK receptor on pre-osteocytes ( to cause osteoclast differentiation.
- Osteo-protegerin: “decoy” RANK receptor that binds and blocks RANKL
