3: Principles of Bone Healing - Carnevale Flashcards Preview

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Flashcards in 3: Principles of Bone Healing - Carnevale Deck (26)
1

breakdown of bone

- 35% organic
- 65% inorganic

2

matrix of bone

95% collagen type I
5% non-collagenous prtns

3

unmineralized bone =

osteoid

4

pluripotent mesenchymal cell that can form osteoblasts

osteoprogenitor

5

cells that initiate mineralization

osteoblasts
- synthesize and transport prtn (like type 1 collagen) and osteoprotegerin

6

what receptor on osteoclasts stimulates osteoclastic bone resorption

RANK receptor
- RANK ligand is produced by osteoblasts

7

become osteocytes when surrounded by matrix

osteoblasts
- osteocytes are matured osteoblasts that regulate daily serum calcium and phosphorus

8

responsible for bone resorption

osteoclasts
- mutliple nuclei
- live in howship lacunae

9

osteoprotegerin

acts as decoy on RANK receptor on osteoclast

10

what are osteoclasts derived from?

hematopoietic progenitor cells

11

role of estrogen in bone growth

- increases bone formation by increasing collagen synthesis by osteoblasts
- prevents bone resorption by inhibiting osteoclast differentiation

12

when is woven bone normal?

- fetal skeleton
- growth plates
- pathologic in adults almost always

13

only type of normal bone in adults

lamellar bone
- highly orderly

14

terms
- end of long bone
- growth plate
- next to growth plate
- shaft
- bone covering (blood vessels, nerves)

epiphysis
epiphyseal plate
metaphsis
diaphysis
periosteum

15

describe bone remodeling cycle

1. osteoclast precursors recruited to bone surface, where thy fuse, differentiate, and mature
2. osteoclasts resorb both organic and inorganic bone matrix
3. resorption phase ends with osteoclast apoptosis
4. in reversal phase, osteoblasts differentiate from mesenchymal precursors, under influence of factros from osteoclasts, and secrete new bone matrix (osteoid)
5. at end of cycle, some osteoblasts have been incorporated into bone as osteocytes and others remain on the surface as quiescent bone-lining cells

16

why do we need vit C for bones?

- maintenance of normal connective tissue
- synthesizes collagen
- responsible for bone formation --> synthesizes organic matrix
- inorganic calcified portion of capillary walls

17

clinical syndrome related to problems with osteoid synthesis AND collagen support of blood vessels

scurvy (vit C deficiency)
- note hemorrhages found around corkscrew hairs
- poor wound healing
- subperiosteal hemorrhage

18

three phases of fracture healing

1 = organization of hematoma at fracture site --> soft, organizing PROCALLUS (hematoma organizing by end of 1st wk, anchorage, no structural rigidity)

2. conversion of procallus to FIBROCARTILAGINOUS CALLUS : reactive mesenchymal cells (deposition of woven bone and new cartilage); 3rd wk; max enlargement

3. replacement of mesencymal cells by OSSEOUS CALLUS; eventually remodeled along lines of weight bearing; completes repair (endochondral ossification forms bony networl; fractured ends bridged by bone callus)

19

"callus"

orderly progression of cartilage into microtrabecular new bone

20

inhibitory factors to fracture healing

- infection
- non union
- inadequate immobilization
- poor circulation, poor nutriton
- drugs (corticosteroids, immunosuppressives, cytotoxic therapy)
- systemic abnormality

21

mechanisms of avascualr necrosis (infarction of bone and marrow resulting from ischemia)

- fracture
- corticosteroids
- uncertain cause idiopathic
- sickle cell disease

22

most common route of osteomyelitis

hematogenous

23

most common agents of osteomyelitis

pyogenic (staph aureus) agents or mycobacterium tuberculosis

24

cause of osteomyelitis in sickle cell patients

salmonella

25

sequestrum

residual necrotic bone post osteomyelitis - may be resorbed or surrounded by rim of reactive bone called involucrum

26

brodie abscess

when well-defined rim of sclerotic bone surrounds residual abscess - viable organisms may persist

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