Osteoporosis Flashcards
What does osteo mean?
Bones
What does porosis mean?
Pores
What is osteoporosis?
- Higher breakdown of bone in comparison to the formation of new bone which results in porus bones.
- Decrease in bone density resulting in a potential to a fracture
What is the hard external layer of the bone called?
Cortical Bone
What is the soft internal layer of the bone called?
- Spongy or Trabecular Bone
What is the spongy bone or trabecular bone composed of?
It is composed of trabeculae
What is the purpose of the trabeculae?
- Framework of beams that provide structural support to the spongy bone / trabecular bone
What is the cortical bone made of ?
Many osteons
What are in the middle of osteons?
Hollowed spaces called haversion canals which contain the blood supply, andinnervation of the blood cells
What are around the haversian canals?
There are concentric lamellae
What are concentric lamellae composed of?
Organic: Collagen
Inorganic: Calcium phosphate (Hydroxyapatite)
What are in between neighboring lamellae?
Spaces called lacunae
What are inside lacunae?
They contain bone cells called osteocytes
What are the steps of bone remodeling?
1) Bone resorption (Osteoclast)
2) Bone formation (Osteoblasts)
During bone remodeling spongy bone is replaced every ?
3-4 years
During bone remodeling compact bone is replaced every?
10 years
What is bone remodeling dependant on?
- Serum Ca2+ levels
How is Serum Ca2+ levels kept in the normal range?
By a balance between
- Parathyroid hormone (PTH)
- Calcitonin
- Vitamin D
What is the parathyroid hormone produced by?
The parathyroid glands in response to low serum calcium
What do the parathyroid hormones increase?
It increases bone resorption to release calcium into the bloodstream
What is calcitonin produced by?
By the thyroid gland in response to high serum calcium (opposes action of PTH)
What does calcitonin promote?
- It promotes bone formation and decreasing bone resorption
What does vitamin D promote?
- It promotes calcium absorption in the gut (Increasing serum calcium)
- promoting bone formation & decreasing bone resorption
What does the balance between these regulatory factors result in? (PTH, vitamin D, and calcitonin)
- Peak bone mass (usually by age 20-29)