3. Bone Healing Flashcards
what % of bone is made up of organic/inorganic component?.
organic matrix- 35%
inorganic component- 65%
what does the organic component of bone consist of?
cells (osteoblasts, etc)
matrix is 95% type 1 collagen
what does the inorganic component of bone consist of?
minerals (e.g. calcium hydroxapatite)
what is unmineralized bone called?
osteoid
what are osteoblasts surrounded by matrix called?
osteocytes
what cell type contains RANKL?
osteoblasts
what cell type contains RANK receptors?
osteoclasts
what is the role of osteoprotegerin?
Osteoprotegerin acts as a decoy by binding to the RANKL (found on osteoblasts) and thus inhibits binding of osteoblast to the RANK receptor on osteoclasts
what are osteoclasts derived from?
hematopoietic progenitor cells
What effect does estrogen have on bone synthesis?
estrogen increases osteoblastic acivity
and prevent bone resorption by inhibiting osteoclast differentiation (via osteoprotegerin)
what effect does decreased estrogen (like in menopause) have on regulating osteoclast activity?
inc. secretion of IL-1, IL-6 , TNF –> increases RANK –> stimulates osteoclast activity
dec levels of osteoprotegerin
what type of collagen forms teh backbone of bone?
type 1 collagen
(woven bone0- deposited randomly
describe the orientation of type 1 collagen in woven bone vs. lamellar bone.
woven bone- random weave
parallel arrangement- lamellar bone
Where is the epiphyses on the bone?
end of long bone
where is teh epiphyseal plate on the bone?
growth plate
whre is the metaphysis on the bone?
next to growth plate
what is the diaphysis ?
shaft of bone
describe the components of cartilage.
inorganic- calcium hydroxyapatite
organic- 80% water and type 2 collagen and proteoglycans
do bones have vasculaturre compared to cartilage?
bones (periosteum) - yes
cartilage- is avascular
give an example of intramembranous bone formation.
(formed directly from mesenchyme)- i.e. skull bone, vertebral column
give ane xample of endochondral bone formation.
(based on cartilaginous model concept of growth plate)- e.g. long finger bones
Vitamin C deficiency leads to what disease?
scruvy (problems related to osteoid synthesis and collagen support of blood vessels)
What are some symptoms of scurvy?
- bruise easily
- bleeding gums
- petechiae around hair follicles
- body hairs curl like corkscrews
What are the 3 stages of fracture healing?
- procallus formation
- conversion of procallus to fibrocartilaginous callus
- replacement of mesenchymal cells by osseous callous
what happens in stage 1 of fracture healing?
procallus formation (hematoma organizes by end of 1st week)
what happens in stage 2 of fracture healing?
conversion of procallus to fibrocartilaginous callus (deposition of woven bone and new cartilage)
*by 3rd week
what happens in stage 3 of fracture healing?
replacement of mesenchymal cells by osseous callus (transition from woven bone to lamellar bone- becomes stronger)
what are the inhibitory factors to fracture healing?
- infection
- non union
- inadequate immobilization
- poor circulation
- poor nutrition
- drugs
- overstressing healing fx
- systemic dz
what are some causes of AVN (avascular necrosis)?
fracture
corticosteroids
idiopathic
thrombosis & embolism (sickle cell dz)
most common bacterial cause of osteomyelitis is what?
staph aureus
which organism is the cause of osteomyelitis in sickle cell patients?
salmonella
what cell type predominates in acute osteomyelitis?
numerous neutrophils
what is sequestrum?
residual necrotic bone seen in chronic osteomyelitis
what is involucrum?
rim of reactive bone that surrounds sequestered bone in chronic osteomyelitis
