Bone Histology

Question 1

What are the three main functions of bone?

Answer 1

Provide protection, structure and storage

Question 2

What is in the extracellular matrix (ECM)

Answer 2

Collagen, Glycoproteins, Proteoglycans (organic)
Hydroxyapatite- forms calcium phosphate (inorganic)

Question 3

What allows for “structure” within the ECM?

Answer 3

Collagen type 1 and hole zones

Question 4

What are the two types of bone?

Answer 4

Cortical/dense
Spongy/trabecular

Question 5

How does spongy/trabecular bone proved structural support (and what law)?

Answer 5

Wolf’s law lead to the unique spongy arrangement of each bone due to the forces that act upon it (ex, long bone vs vertebrae)

Question 6

What are the four bone classifications?

Answer 6

Long bones (tibia)
Short bones (carpal)
Flat bones (skull - increased dense bone)
Irregular bones (vertebrae)

Question 7

Sections of the long bone?

Answer 7

Diaphysis (shaft - includes periosteum)
Metaphysis (transition zone)
Epiphysis (end of bone - includes articular cartilage)

Question 8

Periosteum

Answer 8

Outer lamellae that surround bone
Includes Sharpey’s fibers that communicate with structures inside of the bone
Additionally, includes lymph, blood vessels, and pain receptors

Question 9

Endosteum

Answer 9

Lines trabecular bone

Question 10

Volkmann’s canals

Answer 10

Perforating canals
Has capillaries within

Question 11

Haversian Canal

Answer 11

Central canal that runs with long axis of bone
Also includes capillaries within

Question 12

Interstitial lamellae

Answer 12

Associated with growth and remodeling

Question 13

Circumferential Lamellae

Answer 13

Helps to withstand forces
Outer and inner

Question 14

What are the four main cell types within bone?

Answer 14

Osteoprogenitor cells
Osteoblasts
Osteocytes
OSteoclasts

Question 15

Osteoprogenitor cells

Answer 15

Pluripotent cells
Usually turn into osteoblasts

Flatted/squashed appearance

Question 16

Osteoblasts

Answer 16

Secretes all components of bone and signal hydroxyapatite Cyrus tails to deposit collagen
Eventually turn into osteocytes

Cuboidal/polygonal in shape

Question 17

Osteocytes

Answer 17

Osteoblasts (Haversian system)
Located in the lacunae and process in canaliculi
Canaliculi further communicate via gap junctions.

Hairlike appearance

Question 18

Osteoclasts

Answer 18

Multi nuclear
Help break down bone by releasing HCl and proteases that form howship’s lacuna (ruffle like border where breakdown is happening)

Question 19

Bone Homeostasis

Answer 19

Calcitonin - directly regulates bone formation
Parathyroid hormone (PTH) - indirectly promotes absorption
Vitamin D3 - promotes absorption of bone
Growth hormone and IGF 1 - increases bone formation

Question 20

Two forms of bone formation

Answer 20

Endochondral - cartilage stage first -> interstitial -> appositional (all long bone)

Intramembranous - grows layer by layer (appositional)

Question 21

Osteoporosis Criteria

Answer 21

DXA scan (T-score and Z-score)
- 1 SD and more: normal
-1 to -2.5: low bone mass (osteopenia)
-2.5 and less: osteoporosis