Lecture 6: Bone

Question 1

1. What are the most common hard tissues present in nature and what is the main inorganic compound that forms them?

Answer 1

Tissues: bones and shells Compound for bone: calcium phosphate Ca3(PO4)2 Compound for shells: calcium carbonate CaCO3

Question 2

2. Which elements/groups in hydroxyapatite can be substituted with anions and cations?

Answer 2

Hydroxyapatite Ca5(PO4)3OH Ca - substituted by cations (positive) (Mg, Sr, Ba) PO4 and OH substituted by anions (negative) (F, Br)

Question 3

3. Why can we say that mammals are, in theory, supersaturated with hydroxyapatite?

Answer 3

Humans supersaturated with hydroxyapatite Supersaturated = more solute in solution than in equilibrium And we have excess ions which can substitute the cations and anions We would expect a precipitation when a supersaturated solution is disturbed, but this doesn’t happen with bone as in theory there are proteins which control precipitation.

Question 4

4. Are all bones from vertebrates made of the same material? Explain your answer.

Answer 4

No. Teeth different material to bones Also calcium phosphate has many different phases Different ratios of calcium, phosphate, and hydroxide, as well as different ions substituted in One of the phases is hydroxyapatite Different bones in body have different phases; also changes with age.

Question 5

5. Name 4 hard tissues present in vertebrates.

Answer 5

Bone Cartilage Teeth Sclerotic ring Osteoderm Baculum Otoconia

Question 6

6. Draw the structures of a femur, from the nano to the macro scale.

Answer 6

Question 7

7. Why must implants match the mechanical properties of bone? Please support your answer with examples.

Answer 7

Mechanical properties must match bone Implant puts more stress back onto the bone → bone breaks before the implant does Mechanical stimulus to surrounding tissue changes → resorption