Bone Formation and Growth

Question 1

Things in the
1. Organic
2. Inorganic
matrix of bone

Answer 1

1. Type 1 collagen, proteoglycans, proteins, growth factors

2. Hydroxyapatite, Ca, P, Mg, citrate, K, Na

Question 2

What type of strength does the
1. Organic
2. Inorganic
matrix give to bone?

Answer 2

1. Tensile strength

2. Compression strength

Question 3

Axial skeleton

Answer 3

Skull
Rib cage
Vertebral column

Question 4

Appendicular skeleton

Answer 4

Limbs
Pelvic girdle
Clavicle
Pectoral girdle

Question 5

2 types of bone

Answer 5

Compact/cortical/dense

Spongy/trabecular/cancellous

Question 6

Periosteum

Answer 6

Covers the outer surface of bones (not where the cartilage is)
Has 2 layers: outer (fibroblasts, collagen, nerves, bvs), and inner (periosteal cells)

Question 7

Sharpey fibers

Answer 7

Anchor the periosteum to the bone

Collagen fibers

Question 8

Endosteum

Answer 8

Inner lining of bones
In contact with bone marrow
Often 1 cell layer thick
Endosteal cells (osteoprogenitor cells and bone lining cells)

Question 9

Osteoprogenitor cells

Answer 9

Precursors for osteoblasts

Cannot tell apart from mesenchymal cells on histology

Question 10

Osteoblasts

Answer 10

Bone forming cells

Secrete: type 1 collagen, bone matrix proteins, glycoproteins and proteoglycans, calcify the bone matrix

Question 11

Osteocytes

Answer 11

Bone maintenance cells
Secrete matrix in response to mechanical stress
Degrade matrix to help maintain calcium homeostasis
Completely embedded in the bone matrix (in lacuna, communicate via canaliculi)

Question 12

Osteoclast

Answer 12

Large, multinucleated cells
Derived from monocyte precursors
Responsible for the resorption of bone
Occupy a shallow canal (howship’s lacuna)

Question 13

Osteoporosis

Answer 13

Imbalance between osteoclast mediated resorption and osteoblast mediated bone deposition
Decreased bone mass and enhanced bone fragility

Question 14

Intramembranous bone formation

Answer 14

Develops directly from mesenchyme
No cartilage model precursor
Flat bones of the skull and face, mandible, and clavicle

Question 15

Endochondral bone formation

Answer 15

Cartilage model serves as precursor to bone

Bones of the extremities and axial skeleton that bear weight

Question 16

5 zones of growth plate

Answer 16

Zone of reserve cartilage
Zone of proliferation
Zone of hypertrophy
Zone of calcified cartilage
Zone of resorption

Question 17

Immature bone (woven bone)

Answer 17

No organized lamellae
Contains more cells per unit area
Cells are randomly arranged
Less mineralization
Gets remodelled into either compact or spongy bone

Question 18

Compact bone

Answer 18

Made up of osteons (Haversian system)

Contains a central canal (Haversian canal - contains vascular and nerve supply)

Question 19

Volkmann canals

Answer 19

In compact bone

Connects the endosteum to the periosteum

Question 20

Metaphysis

Answer 20

Area of the bone that flares out

When bone matures and epiphyseal plate closes, clinicans just call the end the metaphysis

Question 21

Metaphyseal inwaisting

Answer 21

Metaphysis gets trimmed as the bone grows so there is not a balloon in the middle

Question 22

Bone metabolizing unit

Answer 22

Contains osteoblasts, osteoclasts, and osteocytes
Cortical bone = osteons
Cancellous bone = trabeculae

Question 23

Wolff’s law

Answer 23

Bone will adapt to the loads it is placed under

If loading on a bone increases/decreases the bone will become stronger/weaker to adapt to that