Bone metabolism L5

Question 1

What percentage of the bone is organic

Answer 1

40%

Question 2

Organic components of bone (2)

Answer 2

Type 1 collagen

non-collagenous proteins

Question 3

Inorganic components of bone (1)

Answer 3

calcium hydroxyapatite

Question 4

What percentage of bone is inorganic

Answer 4

60%

Question 5

other word for trabecular bone

Answer 5

cancellous bone/ spongy bone

Question 6

osteoclasts have multiple

Answer 6

nuclei

Question 7

Osteoclasts formed from

Answer 7

fusion of monocytes haematopoietic

Question 8

Where do osteoclasts sit

Answer 8

Adhere strongly on the bone surface

Question 9

Osteoblasts have how many nuclei

Answer 9

1

mononuclear cell

Question 10

What are they called when osteoblasts burry themselves alive in the new bone matrix they form

Answer 10

osteocytes

Question 11

How is new bone first laid down

Answer 11

non-mineralised osteoid

Question 12

If formation is equal to resorption –>

Answer 12

coupled remodelling

Question 13

osteoid=

Answer 13

type 1 collagen and proteins

Question 14

How much bone do we lose in space per month

Answer 14

1%

Question 15

Mechanisms involved in bone growth and remodelling

Answer 15

PTH
Vitamin D3
Calcitonin

Question 16

approx how much calcium in the body

Answer 16

1000g

Question 17

recommended daily calicum intake

Answer 17

1000mg

Question 18

percentage of calcium in skeleton

Answer 18

99%

Question 19

Serum conc of calcium

Answer 19

2.25-2.6

Question 20

Three fractions of calcium in serum

Answer 20

ionised (50%)
Protein bound (40%)
Complexed calcium (10%)

Question 21

Ca2+ levels maintained by

Answer 21

PTH
Vitamin D
Calcitonin

Question 22

Approx how much phosphate in human body

Answer 22

600g

Question 23

Percentage phosphate in skeleton

Answer 23

85%

Question 24

major ionic species of phosphate in serum

Answer 24

HPO4-2

Question 25

three fractions of inorganic phosphate

Answer 25

``` ionised (55%) Protein bound (10%) Complexed phosphate (35%) ```

Question 26

What is phosphate primarily regulated by

Answer 26

PTH

Question 27

Main route of Vitamin D into body

Answer 27

7-dehydrocholesterol by UV light

Question 28

1st activation of vitamin D

Answer 28

25-hydroxylation in the liver produces 25(OH)D3

Question 29

what is 25(OH)D3 ?

Answer 29

The main circulating metabolite of vitamin D with little biological activity

Question 30

2nd activation of vitamin D

Answer 30

1-hydroxylation in the kidney produces 1,25 (OH)2 vitamin D3

Question 31

What is 1,25(OH2)vitamin D3

Answer 31

the principal hormonal form of vitamin D and is responsible for most of its biological actions

Question 32

What does PTH do in regards to vitamin D

Answer 32

it stimulates and regulates 1,25(OH2) vitamin D3 production

Question 33

What inhibits vitamin D

Answer 33

elevated serum Ca and P

Question 34

(3) actions of 1,25 (OH2) vitamin D3

Answer 34

- increases calcium and phosphate absorption from the intestines - Mobilises calcium and phosphate from bone - Induces marrow monocytes to differentiate into osteoclasts to stimulate bone resorption.

Question 35

what does 24-hydroxylation effect

Answer 35

25(OH)D3 and 1,25(OH2)D3 catabolism

Question 36

what is PTH

Answer 36

parathyroid hormone

Question 37

What structure does PTH have

Answer 37

small polypeptide | 84 amino acids

Question 38

Where and why is PTH secreted?

Answer 38

by the parathyroid gland in response to low plasma Ca2+ levels

Question 39

Effect of high PTH levels

Answer 39

osteoclastic bone resorption | mobilising calcium

Question 40

effect of Intermediate-low PTH levels

Answer 40

osteoblastic bone formation

Question 41

What is the main way through which PTH communicates its effect

Answer 41

predominatly through osteoblasts which communicate with osteoclasts

Question 42

Other general effects of PTH (3)

Answer 42

1. decreased renal calcium excretion 2. Increases renal production of 1,25(OH2) D3 3. increases blood calcium

Question 43

What is PTHrp

Answer 43

parathyroid hormone- related protein

Question 44

What is increased PTHrp production linked with

Answer 44

malignant tumours

Question 45

What does PTHrp do?

Answer 45

major mediator of hypercalcaemia (raised calcium)

Question 46

Calcitonin-->

Answer 46

Reduces bone resorption by activating calcitonin receptors expressed by osteoclasts.

Question 47

Decreased Ca2+ induces-->

Answer 47

PTH secretion

Question 48

Increased Ca2+ induces

Answer 48

Calcitonin secretion

Question 49

Oestrogen-->

Answer 49

reduces bone resorption by inhibiting osteoclastogenesis and inhibiting osteoclast function

Question 50

What expresses oestrogen receptors

Answer 50

osteoblasts and osteoclasts

Question 51

Androgen-->

Answer 51

decreases bone resorption by directly targeting osteoclasts

Question 52

Is Androgen used in men or women

Answer 52

Both

Question 53

Hypercalcaemia=

Answer 53

elevated calcium in circulation

Question 54

Causes of hypercalcaemia

Answer 54

``` primary hyperparathyroidism Malignancy Hyperthyroidism immobilisation vitamin D toxicity ```

Question 55

Primary hyperparathyroidism=

Answer 55

hypercalcaemic state caused by excessive secretion of PTH | Main cause= solitary adenoma

Question 56

Symptoms of hyperparathyroidism

Answer 56

at skeletal sites osteitis fibres cystica

Question 57

What is osteitis fibres cystica

Answer 57

replacement of bone with fibrous tissue

Question 58

What area of skeleton does hyperparathyroidism effect most (2)

Answer 58

Skull and phalanges

Question 59

causes of hypocalcaemia

Answer 59

renal failure vitamin D deficiency prematurity

Question 60

what is secondary hyperparathyroidism

Answer 60

physiological response to hypocalcaemia

Question 61

Cause of osteomalacia and rickets

Answer 61

vitamin D deficiency malabsorption renal disease Lack of sunlight

Question 62

Features of osteomalacia

Answer 62

``` diffuse bone pain localised bone pain around hips Muscle weakness Decreased mineralisation ect ```

Question 63

Osteoporosis =

Answer 63

net loss of bone mass resorption> formation.

Question 64

Osteoporosis most common in

Answer 64

post-menopausal women

Question 65

Osteoporosis treatment

Answer 65

``` Calcium supplementation hormone replacement therapy bisphosphonates calcitonin Selective estrogen-receptors modulators (SERMs) ```

Question 66

Three bisphosphonates

Answer 66

Alendronate, residronate, etridronate

Question 67

What cells secret calcium

Answer 67

C cells in thyroid

Question 68

What cells secret PTH

Answer 68

Chief cells

Question 69

PTH increases calcium travelling to blood from

Answer 69

intestine bone kidney