Bone Pathophysiology

Question 1

What is the purpose of the cortical bone?

Answer 1

Forms the shaft of long bones and the outer shell of flat bones to withstand bending strain

Question 2

What is the trabecular bone?

Answer 2

Network of interconnecting rods and bone

Question 3

What is the purpose of tcabecular bone and where is it found?

Answer 3

Offers resistance to compressive loads and maintain of bone turnover for mineral homeostasis
- Found at the end of long bones and inside flat bones

Question 4

What is the purpose of Woven bone?

Answer 4

Fracture repair in first early years of life

Question 5

In what disease is Woven bone found in?

Answer 5

Paget disease

Question 6

What is the purpose of type 1 collagen?

Answer 6

Forms parallel lamellae of different density

Question 7

What does cortical bone do with type I collagen?

Answer 7

Forms around a central blood supply which communicates via transverse canals

Question 8

What are non collagen proteins?

Answer 8

• Osteopontin
• Osteocalcin
• FIbronectin

Question 9

What does hydroxyapatite consist of?

Answer 9

Calcium and phosphate

Question 10

What is the purpose of Osteoblasts?

Answer 10

Regulate mineralisation and synthesiszes matrix (osteoid)

Question 11

What is the purpose of Osteoclasts?

Answer 11

Resorb bone derived from hameopoietic precursors of the marcophage lineage

Question 12

What is the purpose of Osteocytes?

Answer 12

Respond to mechanical strain undergoing apoptosis or through altered cell signalling activating bone formation with or without prior resorption

Question 13

Where does longitudinal growth occur?

Answer 13

Epiphyseal growth plate

Question 14

What is fused when growth finishes at 18-21?

Answer 14

Epiphysis and metaphysis

Question 15

What is the purpose of regular bone remodelling?

Answer 15

Ensure repair of mricodamage and turnover of calcium for homeostasis

Question 16

What is the remodelling cycle done by?

Answer 16

Basic multicellular unit (BMU)

Question 17

What is the Basic Multicellular Unit?

Answer 17

A temporary functional grouping of cells working together to remove old or damaged bone and replace with new bone

Question 18

Altering the signal to bone remodelling causes….

Answer 18

Localised retraction of bone lining cells and binding of multinucleate osteoclasts to the bone surface followed by bone resorption

Question 19

more notes on bone remodelling

Question 20

How is Calcium homeostasis regulated?

Answer 20

parathyroid horomone (PTH), 1,25 - dihydroxyvitamin D3 on gut, kidney and bone

Question 21

What contributes to bone fragility?

Answer 21

Calcium and vitamin D definciency

Question 22

What does vitamin D deficiency reduce?

Answer 22

Intestinal absorption of calcium

Question 23

What is the mechanism of vitamin D metabolism?

Answer 23

Photoactivation in the skin of 7 dehydrocholesterol to cholecalciferol converted in the liver to 25 hydroxyvitamin D and then in the kidney to 1,25 dihydroxyvitamin D3

Question 24

What is the parthyroid hormone?

Answer 24

84 amino acid horome secreted from the parathyroid glands

Question 25

What is the purpose of parathyroid hormone (PTH)?

Answer 25

Increase renal phosphate excretion and increase plasma calcium

Question 26

How does PTH increase plasma calcium?

Answer 26

- Increasing osteoclastic activity in bone - Increasing intestinal absorption of calcium - Increasing 1a hydroxylation of vitamin D - Increasing renal tubular reabsorption of calcium

Question 27

What can suppress normal PTH response to hydpocalcaemia?

Answer 27

Hypomagnesaemia

Question 28

What is produced by thyroid C cells?

Answer 28

Calcitonin

Question 29

What is the purpose of Calcitonin?

Answer 29

Inhibits osteoclastic bone resorption Increase the renal excretion of calcium and phosphate