Module 3: Bone remodelling Flashcards
What is the primary function of osteoclasts in the bone remodelling cycle?
Osteoclasts resorb bone by digging pits in trabecular bone
What do osteoblasts secrete into the pits created by osteoclasts?
Osteoid (bone matrix)
What are the main components of osteoid?
- Collagen
- Osteocalcin
- Osteonectin
- Phosphoproteins
- Cytokines (IGF and TGF-β)
What process follows the secretion of osteoid by osteoblasts?
Mineralisation of the osteoid
What are hydroxyapatites?
Complex calcium phosphate crystals deposited during mineralisation
Which hormones are involved in bone metabolism and mineralisation?
- Parathyroid hormone
- Vitamin D family
- Various cytokines (e.g., IGF, TGF-β family, interleukins)
What can lead to osteoporosis in terms of hormonal balance?
Bone resorption not balanced by bone formation due to declining oestrogens, therapeutic glucocorticoids, or raised thyroid hormones
Fill in the blank: Osteoblasts are activated by _______.
[osteoclasts]
True or False: Osteoporosis can result from an imbalance between bone resorption and bone formation.
True
What are the precursors of the vitamin D family converted to in the liver?
Calcifediol
Calcifediol is then converted to calcitriol in the kidney.
What is the main hormone produced from calcifediol?
Calcitriol
Calcitriol is the active form of vitamin D.
How does calcitriol affect plasma Ca2+ levels?
Increases plasma Ca2+
This is achieved by mobilizing Ca2+ from bone, increasing intestinal absorption, and decreasing renal excretion.
What is the primary action of parathyroid hormone (PTH)?
Acts on the PTH type 1 receptor on osteoblasts and in the kidney
PTH is crucial for regulating calcium levels in the blood.
What effect does intermittent stimulation of PTH receptors have?
Stimulates bone formation
This is achieved through the use of synthetic PTH analogues.
What hormone is secreted from the thyroid that affects calcium levels?
Calcitonin
Calcitonin plays a role in lowering calcium levels in the blood.
What is the role of calcitonin in calcium resorption?
Reduces Ca2+ resorption from bone
This is accomplished by inhibiting osteoclast activity.
Fill in the blank: The vitamin D family gives rise to true _______.
[hormones]
