Physiology of Bone and Calcium Homeostasis

Question 1

What is hydroxyapatite?

Answer 1

the calcium phosphate which preciptates to the collagen matrix to make bone

Question 2

What are the two types of bone?

Answer 2

trabecular bone and compact bone

Question 3

What is the role of osteoblasts?

Answer 3

to build bone by producing collagen, proteins and enzymes

Question 4

How do bones grow in length?

Answer 4

at the epiphyseal plate chondrocytes divide and then disintegrate leaving a space for osteoblasts to synthesise bone

Question 5

What type of cell are osteoblasts like?

Answer 5

fibroblasts

Question 6

Where are osteoclasts derived from?

Answer 6

haematopoetic stem cells

Question 7

What is the function of osteoclasts?

Answer 7

secretes acid and proteases to dissolve the calcium and collagen matrix of bone

Question 8

What are the roles of calcium?

Answer 8

intracellular signalling, bone matrix, tight junctions, cofactor in coagulation, neuron and muscle excitability

Question 9

Which organs are involved in calcium homeostasis?

Answer 9

bone, kidney and intestine

Question 10

What is the concentration of calcium in the ECF?

Answer 10

2.5mM

Question 11

What is the concentration of calcium in the ICF?

Answer 11

0.001mM

Question 12

What is the role of PTH?

Answer 12

calcium and phosphate release from bone, increases calcium reabsorption in the kidney, decreases phosphate reabsorption in the kidney, activates vitamin D hydroxylation in the kidney

Question 13

What stimulates PTH release?

Answer 13

low plasma calcium

Question 14

What is the chemical nature of PTH?

Answer 14

peptide

Question 15

What is the role of calcitonin?

Answer 15

decreases bone resorption and increases calcium excretion in the kidney

Question 16

What stimulates the release of calcitonin?

Answer 16

high plasma calcium - is not released in normal physiology

Question 17

Where is calcitonin released from?

Answer 17

C cells of the thymus

Question 18

What is the chemical nature of calcitonin?

Answer 18

peptide

Question 19

What steps are required to activate vitamin D?

Answer 19

sunlight in the skin, hydroxylation in the liver and hydroxylation in the kidney

Question 20

What stimulates hydroxylation of vitamin D in the kidney?

Answer 20

PTH and high plasma phosphate

Question 21

What is calcitriol?

Answer 21

1,25-dihydroxycholecalciferol (activated vitamin D3)

Question 22

What are the roles of phosphate?

Answer 22

energy transfer and storage (ATP, cAMP), control of enzymes, transporters and ion channels, DNA and RNA

Question 23

How are calcium and phosphate related?

Answer 23

calcium and phosphate need to be controlled in the blood because if both their levels are high they will precipitate - this is maintained by PTH opposing their reabsorption and excretion in the kidney

Question 24

What causes hyperparathyroidism?

Answer 24

tumour

Question 25

What causes hypoparathyroidism?

Answer 25

autoimmune attack of parathyroid glands or surgical ressection

Question 26

What are the symptoms of hypoparathyroidism?

Answer 26

hypocalcaemia and hyperphosphataemia, neuromuscular excitability - fatal

Question 27

What are the symptoms of vitamin D deficiency?

Answer 27

rickets in children and osteomalacia in adults