bone - hormonal control

Question 0

Which dietary requirements are needed for bone growth

Answer 0

Calcium and proteins

Question 1

which hormones play a role in growth

Answer 1

• insulin - provides glucose energy for growth
• GF and IGF required for protein and cell division
• thyroid hormones - permissive role (play direct role in nervous system developmet
• sex steroids - determines final bone length

Question 2

Explain bone composition

Answer 2

Calcium phosphate crystals precipitate and attach to a collagen fibre lattice

Question 3

Two types of bone

Answer 3

Compact/cortical

Trabecular/spongy

Question 4

What is the important extra role that central bone marrow plays

Answer 4

It is haematopoietic

Question 5

Osteoblasts are modified what

Answer 5

Fibroblasts

Question 6

Function of osteoblasts

Answer 6

Bone forming cells - produce enzymes and osteoid to which hydroxyapatite binds to

Question 7

What extra proteins help osteoblasts in deposition

Answer 7

Osteocalcin

Osteonectin

Question 8

In what part of the long bone does linear growth occur

Answer 8

The epiphyseal plate

Question 9

Where are chondrocytes located

Answer 9

Near the epiphyses in children

Question 10

Function of chondrocytes

Answer 10

Produce collagen - the collagen layer thickens and old chondrocytes disintegrate leaving spaces for osteoblasts to deposit bone

Question 11

What are osteocytes?

Answer 11

The less active form of osteoblasts

Question 12

Explain the structure of osteoclasts

Answer 12

Large, mobile, multinucleate cells derived from haematopoietic stem cells

Question 13

Action of osteoclasts

Answer 13

Secretes acid and protease enzymes to dissolve calcified matrix and collagen support
–> cause calcium to enter the blood

Question 14

Which organs are involved in the hormonal control of the exchange of calcium

Answer 14

Bone
Kidneys
Intestine

Question 15

Which hormones are involved in calcium metabolism

Answer 15

Parathyroid hormone
Vitamin d3
Calcitonin

Question 16

Functions of calcium

Answer 16

• important intercellular signal
• structural functions (physical strength to bone matrix and helps hold cells together at tight junctions)
• cofactor for blood coagulation
• required for normal excitability of neurons and muscles

Question 17

Where are the three pools of calcium storage

Answer 17

Bone matrix - major -99%
Extracellular fluid - as ionized calcium - 0.1%
Intracellular fluid - as free calcium - 0.9%

Question 18

Roles of intracellular calcium

Answer 18

Signal in second messenger pathways

Role in muscle contraction

Question 19

Roles of extracellular calcium

Answer 19

• cement for tight junctions
• role in myocardial and smooth muscle relaxation
• neurotransmitter
• excitability of neurons
• cofactor in coagulation cascade

Question 20

What is the concentration of calcium in the ECF

Answer 20

2.5mM

Question 21

What is the intracellular concentration of calcium

Answer 21

0.001mM

Question 22

Which pool of calcium is free to move to other locations

Answer 22

The calcium in the ECF

Question 23

How much of our dietary calcium is absorbed

Answer 23

1/3

Question 24

Most of our calcium is lost how

Answer 24

In the urine and some in the faeces | There are active transporters in the kidney that reabsorb the majority

Question 25

What are the kidney transporters that actively reabsorb calcium

Answer 25

ECaC Na-Ca antiport Ca-ATPase

Question 26

When is parathyroid hormone released

Answer 26

In response to a decrease in calcium concentration - detected by a Ca sensing receptor in the parathyroid gland

Question 27

General function of parathyroid hormone

Answer 27

- Increases plasma calcium | - decreases plasma phsophate

Question 28

What is the action of parathyroid hormone on the kidneys

Answer 28

Increases calcium reabsorption and decreases phosphate reabsorption

Question 29

How does parathyroid hormone do its function on bones

Answer 29

Drives the actions of OPG and RANKL on osteoblasts to act on osteoclasts to: - increases calcium and phosphate release from the bone into plasma - favours bone resorption by osteoclasts (increases activity of both osteoclasts and osteoblasts)

Question 30

What is the action of parathyroid hormone on the intestines

Answer 30

Indirectly increases calcium and phosphate reabsorption by vitamin D activation

Question 31

Transport of parathyroid hormone in the blood

Answer 31

Dissolved in plasma

Question 32

Explain the biosynthesis of parathyroid hormone

Answer 32

Continuous production with little stored

Question 33

Absence of parathyroid hormone causes...

Answer 33

Hypocalcemic tetany

Question 34

Onset of action of parathyroid hormone

Answer 34

- 2-3 hours for bone - 1-2 days for intestinal absorption - within minutes for kidneys

Question 35

What releases calcitonin

Answer 35

C cells of the thyroid gland

Question 36

When is calcitonin released

Answer 36

In response to high plasma concentrations of calcium (only in extreme hypercalcemia)

Question 37

How is calcitonin transported in the blood

Answer 37

Dissolved in plasma

Question 38

General function of calcitonin

Answer 38

Decreases the activity of osteoclasts --> Decreased calcium and phosphate by reducing calcium release from bone, decreasing calcium reabsorption and increasing renal calcium excretion

Question 39

Target tissues for calcitonin

Answer 39

Bone and kidney

Question 40

What is the interaction of parathyroid hormone and vitamin d

Answer 40

PTH plays a role in turning on the kidney enzymes to get the second hydroxylation of vitamin D to make it active

Question 41

Where do the hydroxylations of vitamin D occur

Answer 41

1st - liver | 2nd - kidney

Question 42

What is the action of vitamin D

Answer 42

Promotes intestinal absorption of calcium and phosphate

Question 43

How is vitamin d transported in the blood

Answer 43

Bound to plasma proteins (steroid hormone)

Question 44

What other hormone other than parathyroid hormone plays a role in vitamin D

Answer 44

Prolactin - stimulates synthesis

Question 45

What is the action of vitamin d at a molecular level

Answer 45

Stimulates the production of calbindin (a Ca binding protein) and CaSR in the parathyroid gland

Question 46

What is the other name for vitamin d

Answer 46

Calcitriol

Question 47

Where is phosphate predominantly found in the body

Answer 47

Bone ECF intracellular

Question 48

Action of vitamin d on phosphate

Answer 48

- Enhances intestinal phosphate absorption in the intestine | - weakly promotes phosphate reabsorption in the kidney

Question 49

What is the action of parathyroid hormone on phosphate

Answer 49

- promotes phosphate excretion and reduced phosphate reabsorption in the kidney - promotes bone phosphate release from the bone

Question 50

What causes PTH hyposecretion

Answer 50

Autoimmune attack of the glands (rare)

Question 51

What happens as a result of a deficiency in vitamin d?

Answer 51

PTH maintains calcium levels at the expense of bone causing bone demineralisation --> rickets or osteomalacia

Question 52

What causes osteoporosis

Answer 52

Long term imbalance of calcium metabolism of bone resorption>bone formation in people of 50 years, predominately in postmenopausal women

Question 53

What are the high risk factors for osteoporosis

Answer 53

``` Inactivity Malnutrition Alcoholism Smoking Postmenopausal Old age Endocrine disorders such as Cushing's ```

Question 54

how do glucocorticoids affectbone

Answer 54

increases osteoclast activity | decreases osteoblast activity

Question 55

how does oestrogen affect bone

Answer 55

- decreases osteoclast proliferation, differentiation and activation - promoting osteoclast apoptosis - increases the life span of osteoblasts and osteocytes

Question 56

what is the definition of osteoporosis

Answer 56

a reduction in bone mass more than 2.5 standa5 standard rd deviations below the normal for healthy 30 year old women

Question 57

what is the definition of osteopaenia

Answer 57

a reduction in bone mass 1-2.5 standard deviations below the normal for healthy 30 year old women

Question 58

which part of the bone mass is lost in osteoporosis

Answer 58

both cells and matrix

Question 59

how does osteoporosis cause increased risk of fracture

Answer 59

loss of trabeculae and thinning reduce the cross-sectional area so that loads on bone are relatively greater