Bone Histo

Question 1

Compact bone

Answer 1

Hard outer cortex surrounding spongy bone

Lamellar bone

Question 2

Spongy bone

Answer 2

Cancellous/Trabecular
Lamellar/woven
Spaces for bone marrow
Inner layer

Question 3

Woven bone

Answer 3

Immature/premature
Turns into lamellar bone
Loose collagen fibers
More cells, less mineral content
Forms during fracture repair
Forms quickly, not very strong

Question 4

Lamellar bone

Answer 4

Mature/secondary
Does not stain with H&E staining
Forms slowly, strong
Adult form of bone
Regular parallel array of collagen fibers

Question 5

Bone matrix

Answer 5

90% ECM, 10% water
Organic
Inorganic

Question 6

Organic bone matrix

Answer 6

35% of bone
90% type I collagen fibers
Has ground substance made of: proteoglycans, glycoproteins, cytokines/growth factors, vitamin K dependent proteins
Osteoid (unmineralized bone)

Question 7

Inorganic bone matrix

Answer 7

Makes up most of bone
Calcium phosphate and hydroxyapatite
Creates hardness/stiffness

Question 8

Osteoprogenitor cells

Answer 8

Make osteoblasts
Mesenchymal in origin
Able to differentiate and proliferate
Inner layer of periosteum and endosteum

Question 9

Osteoblasts

Answer 9

Epithelial-like cells with cuboidal or columnar shape
Alkaline phosphatase that goes away when they turn into osteocytes
Deposit osteoid and control their mineralization

Question 10

Osteocytes

Answer 10

Osteoblasts within lacunae surrounded by the osteoid matrix they deposited
Has lamellae—>canaliculi to get nutrients
Life of bone matrix depends on these

Question 11

Osteoclasts

Answer 11

Macrophage/monocytes lineage
Monocytes traveling in blood that became these when they entered bone
Create an acidic environment with H+ATPase to break down bone
Important during bone remodeling/renewing
In Howship’s lacunae

Question 12

Periosteum

Answer 12

Surrounds bone except for articular surfaces
Nutrition of osseous tissue
New cellls for growth and repair
Inner layer:
Osteoprogenitor cells
Outer layer:
Nerves and blood supply
Fibroblasts and collagen
Sharpers fibers: anchoring collagen fibers that go through lamellae

Question 13

Endosteum

Answer 13

Inner layer of bone
Contains osteoprogenitor cells
Surrounds spongy bone

Question 14

Osteon

Answer 14

Concentric lamellae surrounding longitudinal vessels

Question 15

Interstitial lamellae

Answer 15

Separates one osteon from another

Has cement line separating osteons

Question 16

Outer circumferential lamellae

Answer 16

Sits under periosteum

External surface of compact bone

Question 17

Inner circumferential lamellae

Answer 17

Adjacent to endosteum

Internal surface of bone

Question 18

Osteocytes

Answer 18

Surrounded by canaliculi that project into the lamellae
Occupy a lacunae
Bone cells that support the matrix

Question 19

Haversion canal

Answer 19

Longitudinal vessels in the middle of osteons

Question 20

Volkmann’s canal

Answer 20

Transverse vessels that connect Haversion canals

Question 21

Intramembranous Ossification

Answer 21

Mesenchymal cells—> bone
Entrapment of first osteocytes; formation of periosteum
Surface bone is filled in by bone deposition, converting spongy bone to compact bone
Spongy bone still exists in middle layer

Question 22

Endochondral ossification

Answer 22

Mesenchyme develops in hyaline cartilage covered with perichondrium
Perichondrium stops producing chondrocytes and starts producing osteoblasts
Chondrocytes in the middle start to enlarge= primary ossification center
Chondrocytes die in this area
Blood vessels penetrate the primary ossification center
Produces the primary marrow cavity
Spongy bone formed
Osteoclasts follow the dying chondrocytes that are moving toward the end of the bone and eat them, enlarging the marrow cavity
Chondrocytes enlargement and death create a secondary ossification center in the epiphysis
Epiphysis fills with spongy bone
Cartilage is limited to the epiphyseal plate

Question 23

Zones of endochondral ossification

Answer 23

In direction of growth
Zone of resorption
Zone of calcified cartilage
Zone of hypertrophy
Zone of proliferation
Zone of reserved cartilage

Question 24

Bone fracture repair

Answer 24

Formation of fracture hematoma gets rid of necrotic bone pieces by inflammatory mediators
Fibrocartilaginous callus formation via chondroblasts
Bony callus formation via osteoblasts
Bone remodeling via osteoclasts

Question 25

Achondroplasia

Answer 25

AD mutation if FGFR3
FGFR3 normally inhibits endochondrial growth, but it is prematurely activated and prevents growth earlier in these individuals
Dwarfism
Shortening of extremities
Normal trunk length

Question 26

Rickets

Answer 26

In children
calcium or Vitamin D deficiency during growth—>defect in mineralization of cartilage in growth plate
Bowed lower limbs
Bowing of distal radius and ulna
Delayed closure of fontanelles

Question 27

Osteomalacia

Answer 27

Adult form of rickets
Progressives softening and bending of bone
GI disease or Vit D deficiency
Bone and joint pain
Muscle weakness
Fracture

Question 28

Osteoporosis

Answer 28

Imbalance between osteoclasts resorption of bone and osteoblasts deposition of bone
Elderly and postmenopausal females
Easy fractures