Lecture 2- Bone

Question 1

Periosteum

Answer 1

Located along the outer surface of bone except along articular surface

Has outer fibrous layer

Has inner osteogenic (cambium) layer composed of osteoprogenitor cells and osteoblasts. This layer participates in appositional growth

Question 2

Cells in bone

Answer 2

Osteoblasts- responsible for bone formation; produce matrix (osteoid), type 1 collagen and other proteins; occur in groups along surfaces; *osteoid seam found between active osteoblasts and bone surface

Osteocytes- embedded in lacunae in matrix; osteoid becomes calcified; orchestrates bone loss or gain as needed

Lining cells- flattened cells covering resting bone surface; can convert to osteoblasts under certain stimuli (PTH)

Osteoclasts- multinucleated; responsible for bone resorption; located in Howship’s lacunae; activity increases with PTH, decreases with estrogen and calcitonin; regulated by RANK/RANKL/OPG pathway

Question 3

Resorption of bone

Answer 3

1. Decalcification of matrix
2. Digestion of organic components (collagen, proteoglycans, etc)
   Requires cathepsins

Question 4

Bone matrix and mineral

Answer 4

Amorphous ground substance- chondroitin sulfate, keratan sulfate, and hyaluronic acid

Collagen fibers (type 1)

Minerals- calcium and phosphorus