Bone Histology

Question 1

Woven bone

Answer 1

Immature.
Replaced by lamellar bone.
Loose arrangement of collagen.
More cells, less mineralization.
Forms during fx or remodeling.

Question 2

Lamellar bone

Answer 2

Mature.
Parallel arrangement of collagen.
No visible on H/E staining.
Forms most adult bone.

Question 3

Organic bone vs. inorganic bone

Answer 3

Organic bone: type 1 collagen. 
Ostoid (unmineralized)
35% of bone matrix.
Ground substance (proteoglycans, glycoproteins, GFs, cytokines, etc)
Inorganic: CaPO4.
65% of matrix.
Creates stiffness.

Question 4

Osteoprogenitor cells

Answer 4

Mesenchymal origin that have SC properties.
Found in inner periosteum and endosteum.
Give rise osteoblasts.
Reactivate during times of repair.

Question 5

Osteoblasts

Answer 5

Deposit ostoid and control mineralization.

Gve strong chemical rxn for alkaline phosphatase.

Question 6

Osteocytes

Answer 6

Arise when osteoblasts trap themselves inside of the bone they made.
Highly branched.

Question 7

Osteoclasts

Answer 7

Derived from moncytes/macrophages.
Generate an acidic environment via H-ATPase. Degredartion via Cathepsin K protease.
Reside in Howship’s lacuna.

Question 8

Endosteum

Answer 8

Covers spongy walls.
Extends into cavities of bones.
Has osteoprogenitor cells.

Question 9

Anatomy of the Osteon

Answer 9

Interstitial lamellae
Outer circumfenetial lamellae
Inner cirumferential lamellae
Osteocytes
Haversion canal
Volkmann's canal
Lacuna
Canaliculi

Question 10

Achondroplasia

Answer 10

Most common form of dwarfism.
Shirt extremities, normal trunk, small midface, altered spinal curvature.
No change in intelligence.

Question 11

Osteoporosis

Answer 11

Progressive loss of normal bone density.
Caused via imbalance of osteoclasts deposition.
Easy fxs.