Flashcards in Bone and new markers Deck (55)
What part of the bone is corticoid bone?
Hard, out layer
What part of the bone is the trabecular bone?
Spongy, inner layer
What do osteoblasts do?
What do osteoclasts do?
What is the function of the trabecular bone?
Bone marrow -
What is the extracellular part of bone composed of?
Inorganic matrix - hydroxyapatite, minerals e.g. calcium, phosphate
Organic matrix - collagen
What is bone before it is mineralised?
What mineralises bone?
(calcium-phosphate, hydroxide salt)
Why is bone considered a dynamic tissue?
Constantly being remodelling
Osteoblasts produce and secrete metric and help with mineralisation
Osteoclasts reabsorb (both clasts/blast actions = linked)
What do osteoblasts do?
Make osteoid (non-mineralised organic matrix - mainly collagen)
Make hormones (osteocalcin), matrix proteins and alkaline phosphatase
What are osteoblasts called when buried underneath/trapped within matrix?
What enzymes do osteocytes produce?
Tartrate resistant acid phosphatase (TRAP)
What main hormone is osteoclasts regulated by?
What ligands/proteins helps with osteoclast maturation and activity
RANK (produced by osteoblasts)
What are the function of osteocytes?
Maintain bone matrix turnover
What is the bone remodelling process?
Osteocyte -> reabsorption pit -> osteoblast -> produce osteoids -> mineralisation (hydroxyapatite) -> osteocyte
Why is reduced bone mass related to menopause?
Loss of oestrogen
What also happens as you get older (i.e. osteoclastic - osteoblastic activity)
Osteoclastic activity increases - balance tipped to bone reabsorption
What diagnostic test is used to investigate bone gross structure?
What investigative technique is used to assess bone mass? (I.e. calcium levels)
What biomarkers indicate bone formation (i.e. pro-osteoblastic activity)
Pro collagen type I phosphatase (P1NP)
What markers could be used for bone reabsorption
Cross linked telopeptides of type 1 collagen (CTX/NTX)
What markers could be used for osteoclastic activity? (i.e. enzymes)
TARP (tartrate acted resistant phosphatase)
What produces alkaline phosphatase?
Osteoblasts - indicator of bone remodelling
When is high levels of all pos observed?
-Pagets disease of bone
What is pro collagen type I phosphatase an indicator of? what is it a particularly good marker?
Indicates osteoblastic activity
Good because it is a very stable marker - no diurnal variation/no affected by food intake
What does cross linked telopeptides of Type I collagen indicate? What can their use be problematic?
Indicates bone reabsorption e.g. adolescence, menopause, hyperthyroidism
However diurnal variation/affected by food intake
What are the problems with using bone markers?
Not disease specific
Not specific - type I collagen which is widely distributed in body
What is a DEXA scan used to determine? What do the T scores indicate
T score - number of SD's away
normal = -1+
Osteopenia = -1 - -2.5