Bone metabolism Flashcards
What are the 3 types of bone cells?
- osteocytes
- osteoblasts
- osteoclasts
What are the role of osteocytes?
Responsible for the communication between bone and the environment - respond to mechanical stimulation by sensing exercise on the bones by building bone when stresses are high and losing bone when stresses are low
What are the role of osteoblasts?
Responsible for bone formation
They synthesize organic matrix/osteoid including collagen and other proteins, and
lay down Ca phosphate mineral as hydroxyapatite crystals along the collagen fibres
What are the role of osteoclasts?
Responsible for bone resorption
Regulate osteoblast activity (by resorbing bone)
What is osteoporosis?
A quantative reduction of bone in the skeleton as a tissue
What are the aetiology (causes) of osteoporosis?
Nutrition and lifestyle - Ca and Vitamin D deficiencies, severe lack of physical activity
Oestrogen deficiency - after menopause for women and in ageing with men
Inflammation, cancer and drugs
How does oestradiol (oestrogen) regulate bone metabolism?
Regulates Ca in kidney, gut and bone on osteoblasts to suppress osteoclast activity and bone resorption
How does estrogen deficiency effect bone metabolism eg after menopause?
After menopause there is loss of Ca through the urine and less is absorbed from the diet, and bone resorption increases markedly
How can osteoporosis be prevented?
Supplementation
- minimum dietary Ca levels to maintain balance
- critical vitamin D levels to reduce bone resorption
Exercise - directly stimulate bone formation and increase muscle strength to improve stability (osteocytes)
What are the 2 types of biochemical bone markers?
Bone resorption - type 1 collagen breakdown products measured in serum and urine
Bone formation - osteoblast products
