2.3 Composition & Composition of Bone

Question 1

Microanatomy - Osseous Tissue

Answer 1

• DYNAMIC tissue: turnover 20% of your skeleton per year
• supporting connective tissue: *contain specialized cells
  *contain extracellular protein fiber
  *contain ground substance

Question 2

Osteogenic

Answer 2

= stem cells
- formed from mesenchyme (embryonic connective tissue)
- give rise to osteoblast
Osteogenic cells -Mitosis-> Daughter osteogenic cells -Differentiation-> Osteoblasts

Question 3

Osteoblasts

Answer 3

= builders
- immature versions of bone cells
- secrete organic component of extracellular matrix
- initiate calcification: remove calcium from blood and deposit it within matrix via exocytosis

Question 4

Osteocytes

Answer 4

=maintenance crew
- mature bone cells
- maintain existing matrix in response to: *bone density needs
*blood calcium & phosphate levels
- acts as strain sensors –> regulate remodeling in response to mechanical stress

Question 5

Osteoclasts

Answer 5

= destroyers
- derived from blood stem cells (NOT osteogenic cells)
- contain resorption bays where they secrete acid & proteolytic enzymes to dissolve matrix (bone resorption):
*dissolved materials (calcium, phosphate) absorbed into blood
*structure –> function - ruffled border increases surface area
- resorption bay: pit in compact bone where bone remodeling is active
- ruffled border: exaggerated portion of osteoblast membrane where enzymes & acid are released & broken-down minerals are brought into the cell

Question 6

Osseous matrix- Organic

Answer 6

• 1/3 of the matrix
• glycosaminoglycans (GAGs)
• collagen fibers

Question 7

Glycosaminoglycans - organic

Answer 7

• trap water due to negative charge
• glycoproteins (polysaccharide + protein)
  ex: chondroitin sulfate, hyaluronic acid
• proteoglycans

Question 8

Collagen fibers

Answer 8

• fibrous protein arranged in a helical form (Type 1 collagen)
• very resistant to pulling forces
• provides flexibility & a framework for deposition of calcium crystals

Question 9

Type 1 Collagen fibers

Answer 9

• most abundant collagen and also the most abundant protein in the human body
• found in bones as well as fibrous tissues like tendons, ligaments, and skin
• glycine combines with other amino acids to make a collagen polypeptide.
  3 collagen polypeptides coil around each other to make tropocollagen