Bone Flashcards
What is cortical bone?
The compact external layer of bone
What is the structure of the cortical bone?
Osteons surrounded by concentric lamellae of bone matrix
What is cancellous bone?
A highly porous network of thin porous trabeculae
What is the main role of cancellous bone?
Mineral exchange it is 4x more active than cortical bone
What is bone matrix made up of?
Collagen 1, collagen cross links and hydroxyapatite crystals
What is the role of collagen 1?
It provides the elasticity of the bone
What is the role of collagen cross links?
It attaches the collagen 1 molecules together
What is the role of hydroxyapatite crystals?
They are a source of Ca2+ and phosphorus and provides rigidity to the bone
What causes brittle bones?
When there is too much minerals
What causes bendy bones?
When there isn’t enough minerals
Why does bone matrix need to be turned over?
- Obtain optimal shape
- Repair damage
- Prevent accumulation of aged tissue
- Supply calcium and phosphorous for homeostasis
What are osteoblasts?
Cells which builds bone by forming osteoid and then mineralising it
What are osteoblasts derived from?
Mesenchymal lineage
What happens to osteoblasts once they finish their jobs?
Terminally differentiate into an osteocyte
What is the serum marker of bone formation?
P1NP
What is P1NP
The serum marker of bone formation produced during matrix formation
What are osteoclasts?
Cells which breakdown bone matrix by secreting acid to demineralise and secreting enzymes to breakdown collagen matrix
What is the serum marker of bone resorption?
CTX
What is CTX?
The serum marker for bone resorption produced during matrix degradation
What are osteoclasts derived from?
Hematopoietic pre-cursor cells
What are osteocytes?
Release factors which control osteoclast and osteoblast formation and activity
What do osteocytes respond to?
It is a mechano sensing cell which responds to load in tissue
What are osteocytes derived from?
Osteoblasts that have been embedded within bone
What 5 bodily functions is Ca2+ essential for?
- Neurotransmitter release
- Contraction of muscle
- Blood coagulation
- Tertiary structure of enzymes
- Mechanical integrity of the skeleton
What is hypocalcemia?
When calcium levels are too low
What can hypocalcemia lead to?
Muscle spasms and seizures
What is hypercalcemia?
When calcium levels are too high
What can hypercalcemia lead to?
Nausea, osteoporosis and kidney failure
What are the two key hormones that regulate calcium?
Parathyroid hormone and calcitriol
What are parathyroid glands?
Four glands found on the posterior surface of the thyroid gland that produces parathyroid hormone PTH
What does PTH do?
- Reduced calcium excretion in the kidney
- Increases the release of calcium from bone through resorption
- Stimulate calcitriol production in the kidney
What is calcitriol?
Is an active form of vitamin D
What does calcitriol do?
- Increases intestinal calcium absorption
- Supports renal reabsorption of calcium
- Increase bone resorption and decrease bone formation
What is osteoporosis?
Compromised bone structure and strength predisposing to an increased risk of fracture
At what age is peak bone density roughly?
30
Why do women lose bone density faster than men?
The decrease of estrogen during menopause increases bone resorption and decreases bone formation
Why do men and women both start to get reduced bone density as the age?
Testosterone increases bone formation and is a source of estrogen however the amount of testosterone decreases with age
What are the primary risk factor of osteoporosis?
Age, gender, previous fracture and hieght/BMI
