Bone

Question 1

What is cortical bone?

Answer 1

The compact external layer of bone

Question 2

What is the structure of the cortical bone?

Answer 2

Osteons surrounded by concentric lamellae of bone matrix

Question 3

What is cancellous bone?

Answer 3

A highly porous network of thin porous trabeculae

Question 4

What is the main role of cancellous bone?

Answer 4

Mineral exchange it is 4x more active than cortical bone

Question 5

What is bone matrix made up of?

Answer 5

Collagen 1, collagen cross links and hydroxyapatite crystals

Question 6

What is the role of collagen 1?

Answer 6

It provides the elasticity of the bone

Question 7

What is the role of collagen cross links?

Answer 7

It attaches the collagen 1 molecules together

Question 8

What is the role of hydroxyapatite crystals?

Answer 8

They are a source of Ca2+ and phosphorus and provides rigidity to the bone

Question 9

What causes brittle bones?

Answer 9

When there is too much minerals

Question 10

What causes bendy bones?

Answer 10

When there isn’t enough minerals

Question 11

Why does bone matrix need to be turned over?

Answer 11

• Obtain optimal shape
• Repair damage
• Prevent accumulation of aged tissue
• Supply calcium and phosphorous for homeostasis

Question 12

What are osteoblasts?

Answer 12

Cells which builds bone by forming osteoid and then mineralising it

Question 13

What are osteoblasts derived from?

Answer 13

Mesenchymal lineage

Question 14

What happens to osteoblasts once they finish their jobs?

Answer 14

Terminally differentiate into an osteocyte

Question 15

What is the serum marker of bone formation?

Answer 15

P1NP

Question 16

What is P1NP

Answer 16

The serum marker of bone formation produced during matrix formation

Question 17

What are osteoclasts?

Answer 17

Cells which breakdown bone matrix by secreting acid to demineralise and secreting enzymes to breakdown collagen matrix

Question 18

What is the serum marker of bone resorption?

Answer 18

CTX

Question 19

What is CTX?

Answer 19

The serum marker for bone resorption produced during matrix degradation

Question 20

What are osteoclasts derived from?

Answer 20

Hematopoietic pre-cursor cells

Question 21

What are osteocytes?

Answer 21

Release factors which control osteoclast and osteoblast formation and activity

Question 22

What do osteocytes respond to?

Answer 22

It is a mechano sensing cell which responds to load in tissue

Question 23

What are osteocytes derived from?

Answer 23

Osteoblasts that have been embedded within bone

Question 24

What 5 bodily functions is Ca2+ essential for?

Answer 24

• Neurotransmitter release
• Contraction of muscle
• Blood coagulation
• Tertiary structure of enzymes
• Mechanical integrity of the skeleton

Question 25

What is hypocalcemia?

Answer 25

When calcium levels are too low

Question 26

What can hypocalcemia lead to?

Answer 26

Muscle spasms and seizures

Question 27

What is hypercalcemia?

Answer 27

When calcium levels are too high

Question 28

What can hypercalcemia lead to?

Answer 28

Nausea, osteoporosis and kidney failure

Question 29

What are the two key hormones that regulate calcium?

Answer 29

Parathyroid hormone and calcitriol

Question 30

What are parathyroid glands?

Answer 30

Four glands found on the posterior surface of the thyroid gland that produces parathyroid hormone PTH

Question 31

What does PTH do?

Answer 31

- Reduced calcium excretion in the kidney - Increases the release of calcium from bone through resorption - Stimulate calcitriol production in the kidney

Question 32

What is calcitriol?

Answer 32

Is an active form of vitamin D

Question 33

What does calcitriol do?

Answer 33

- Increases intestinal calcium absorption - Supports renal reabsorption of calcium - Increase bone resorption and decrease bone formation

Question 34

What is osteoporosis?

Answer 34

Compromised bone structure and strength predisposing to an increased risk of fracture

Question 35

At what age is peak bone density roughly?

Answer 35

30

Question 36

Why do women lose bone density faster than men?

Answer 36

The decrease of estrogen during menopause increases bone resorption and decreases bone formation

Question 37

Why do men and women both start to get reduced bone density as the age?

Answer 37

Testosterone increases bone formation and is a source of estrogen however the amount of testosterone decreases with age

Question 38

What are the primary risk factor of osteoporosis?

Answer 38

Age, gender, previous fracture and height/BMI