Bone structure and function Part 2 Flashcards
What are the 4 types of bone cell
osteoblasts
osteoclasts
osteocytes
osteoprogenitor cells
What do osteoblasts do?
Lays down bone matrix
- What do osteoclasts do?
resorb bone
What do osteocytes do?
maintains matrix
- What do osteoprogenitor cells do?
give rise to osteoblasts involved in remodelling
What lineage do osteoclasts come from?
monocyte/macrophage lineage
Give 2 specific ways that osteoblasts perform their function
- Secretes organic bone matrix AKA osteoid
- Mediates mineralisation of osteoid
what is mineralisation of osteoid?
deposition of inorganic salts into the osteoid
What shape are osteoblasts?
Cuboidal shape
- Give 2 things that osteoblasts secrete
- collagen
- matrix vesicles
- what do the matrix vesicles secreted by osteoblasts contain
- Alkaline phosphatase and other enzymes and proteins that control the availability of calcium and phosphate
- What happens when the levels of calcium and phosphate levels increase to a sufficient level?
hydroxyapatite crystals are precipitated
- What are gap junctions?
Long cytoplasmic processes connecting to osteocytes to other osteocytes and osteoblasts
- What are osteocytes surrounded by?
surrounded by mineralised matrix
- Where do osteocytes sit in?
They sit in Lacunae
- How do osteocytes receive nutrients?
Extracellular bone fluid surrounding lacunae that allows nutrient diffusion through the bony channels
- What is the name of the bone channels in bone
canaliculi
- What is stress information in osteocytes?
when osteocytes respond to tiny currents generated when bone is deformed
- What do osteocytes mediate in terms of calcium?
Mediates short term release of calcium from bone
- What is a histological feature of osteoclasts?
They are Multinucleate
- What do osteoclasts attach to, what does it do and what does this leave behind?
attaches to bone surface, resorbing bone which leaves a pit behind
- What is the name for the pit left behind by osteoclasts?
Howships lacuna
- What do osteoclasts work with osteoblasts for to do?
Work with osteoblast to regulate bone turnover and remodelling
- Name 2 features of osteoclasts found on its surface
- Actin clear zone
- Ruffled border
- What does the ratio of RANKL to osteoprotegrin determine?
determines bone resorption
explain bone Mineralisation
- Osteoblasts secrete collagen and matrix vesicles
- Matrix vesicles contain enzymes and proteins to control availability of calcium and phosphate
- Needs to increase to a level where hydroxyapatite is precipitated