Lecture 2

Question 1

Bone Composition

Answer 1

Calcium Phosphate Crystals (hydroxyapatite)

Water

Organic Protein (Collagen Fibers arranged in sheets, 85-90% of protein in bone, flexibility)

Question 2

Main types of bone tissue

Answer 2

Cortical (Compact) Bone

Trabecular (Spongy or Cancellous) Bone

Question 3

Cortical (Compact) Bone

Answer 3

80% of skeletal mass
Dense outer bone surface
Thickest in the bone shaft
Porosity 5-10%

Question 4

Trabecular (Spongy or Cancellous) Bone

Answer 4

3D internal structure of bony rods/plates
Concentrated in the bone ends inside the joints
Porosity 75-95%

Question 5

Bone Lining Cells

Answer 5

Line all bone surfaces and control movement of materials in and out of the bone

Periosteum
Endosteum

Question 6

Osteoblast: Bone Forming Cell

Answer 6

Derived from bone lining cells
Secrete bone matrix, collagen, and other organic bone matrix components
Move inorganic minerals into the matrix

Question 7

Osteocyte: Mature Bone Cell

Answer 7

Osteoblasts that have become embedded in lacunae
Maintain bone tissue, sense mechanical strain
Communicate with each other through canaliculi

Question 8

Osteoclasts: Bone-resorbing cell

Answer 8

Related to white blood cells
Break down bone tissue
Release minerals stored in bone (Calcium, potassium)

Question 9

Bone Modeling

Answer 9

• Change in bone size and shape through addition and/or removal of bone at the periosteal or endosteal surfaces
• Highest rate during growth, much less after maturity
• Involves independent actions of osteoclasts and osteoblasts

Question 10

Bone Remodeling

Answer 10

• Replacement of old bone by new bone to repair damage and prevent fatigue
• No net change in bone amount, size or shape
• Occurs throughout life, but is substantially reduced after growth stops
• Involves combined actions of osteoclasts and osteoblasts (basic multicellular unit)

Question 11

Woven Bone

Answer 11

Laid down very quickly: fetus, fracture repair
Almost random collagen orientation and mineral arrangement
Quite porous and mechanically weak

Question 12

Lamellar Bone

Answer 12

Laid down slowly
Collagen fibers and mineral arranged in sheets called lamellae
Lamellae house osteocytes in their lacunae

Question 13

Lamellar Bone Organization: Primary Bone, Circumferential Lamellae

Answer 13

Laid down after initial rapid fetal growth
Secreted by bone lining cells of the periosteum
Wrap around the outside of the bone, parallel to the outer edge.

Question 14

Lamellar Bone Organization: Primary Bone, Primary Osteons

Answer 14

Start forming in childhood
Form from mineralized cartilage
Ring like structures of concentric lamellae around a central blood vessel canal
No clearly defined perimeter

Question 15

Secondary Osteons: Haversian Systems

Answer 15

Accumulate throughout life
Concentric lamellae around a central haversian canal
Result of remodeling through existing bone
Surrounded by a distinct cement line
Collagen fibers roughly parallel in each lamellae

Question 16

Haversian canals are connected by

Answer 16

Volkmann’s peripheral canals

Carry blood vessels and nerves