Bones-Basics

Question 1

What are the functions of bone?

Answer 1

Weight bearing/support
Protection (e.g. skull: brain, vertebrae: spinal cord)
Mineral store
Blood formation (red bone marrow)

Question 2

What is in bone?

Answer 2

compact/ cortical bone (shell of bone almost)
spongy/trabecular bone (in middle , close to joint)
blood vessels
medullary cavity (with yellow bone marrow)
membranes (periosteum and endosteum)

Question 3

Where would you find periosteum and endosteum?

Answer 3

Periosteum? -outside bone
Endosteum? -inner side of bone

Question 4

Characteristics of Osteons or Haversian systems?

Answer 4

Compact bone organised in circular structures
Central Haversian canal and horizontal perforating/Volkmann’s canals (have blood vessels)
Osteocytes and concentric rings of bone matrix (lamellae) around Haversian canal

Question 5

Spongy bone characteristics?

Answer 5

Also called cancellous or trabecular bone or diploe
Less dense than compact bone
Network of lamellated trabeculae filled with bone marrow
No Harversian systems!
Orientation of trabeculae reflect main directions of mechanical forces

Question 6

Bone composition?

Answer 6

Cells

Osteoclasts
Osteoblasts
Osteocytes

Extracellular matrix
~45% hydroxyapatite crystals (complex form of calcium phosphate)
~35% Collagen (Type I)
~20% Water

Question 7

What do minerals do in bone? (hydroxyapatite)

Answer 7

Make bone stiff & able to support structures
High strength under compression (like concrete)

Question 8

What does collagen do in bone?

Answer 8

Gives bone some flexibility & reduces risk of fracture
High strength under tension (like steel)