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Physiology for Engineers > Lecture 14: Bone Physiology 2 > Flashcards

Lecture 14: Bone Physiology 2 Flashcards

1
Q

What are the two main purposes of bone tissue?

A
  1. Mechanical support and protection
  2. Store and maintain mineral homeostasis
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2
Q

What are the processes bones are closely linked to?

A

-Calcium, Phosphate
-Formation of bone and teeth
-Regulation of Vitamin D, Parathyroid Hormone (PTH) and Calcitonin

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3
Q

Calcium levels are controlled between _____ and ______.

A

extracellular fluid and three organs

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4
Q

What is the process of bone remodeling?

A

breaking down hydroxyapatite by osteoclasts

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5
Q

Slide 4

A
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6
Q

Slide 5

A
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7
Q

What are 3 hormones that control calcium?

A

Vitamin D, Parathyroid hormone (PTH), and Calcitonin

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8
Q

Where is vitamin D produced?

A

skin, kidneys

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9
Q

Where does vitamin D act?

A

intestines

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10
Q

What is the structure of vitamin D?

A

Cholestrol

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11
Q

Is vitamin D lipid or water soluble?

A

Lipid-soluble

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12
Q

What are the major actions of vitamin D?

A
  • Promotes intestinal absorption of calcium and phosphate
  • Increases renal reabsorption of calcium and phosphate (minor)
    *Enhances bone calcification (by increasing calcium transport,
    activating osteoblasts?)
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13
Q

What do chief cells secrete?

A

Parathyroid hormone (PTH)

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14
Q

What are the major actions of PTH?

A

*Increase plasma calcium
*Increase production of 1,25 Dihydroxycholecalciferol
in the kidney
*Increase calcium/phosphate absorption from bone
-Activates osteocytes, activates osteoclast proliferation
* Inhibit calcium excretion from kidneys
* Increase phosphate excretion from kidneys
* Stimulates osteolysis (so excessive PTH weakens bone and induces high calcium levels such as with Primary Hyperparathyroidism

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15
Q

What does PTH stimulate the release of?

A

Calcium

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16
Q

True/False: Parathyroid Hormone (PTH) stimulates Osteoclast activity and bone resorption indirectly

A

True

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17
Q

Do osteoclasts have PTH receptors?

A

no

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18
Q

What happens as a result of Osteoclasts not having PTH receptors?

A

Osteoblasts (build bone)
signal Osteoclast precursors to form mature Osteoclasts (chew bone)

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19
Q

RANKL

A
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20
Q

What is osteoprotegerin (OPG) and how is it produced?

A

A cytokine that inhibits bone resorption and is formed by osteoblasts

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21
Q

What is the role of OPG?

A

acts as a “decoy” and binds to RANKL, preventing interaction with its receptor; therefore,
inhibiting differentiation of Preosteoclasts into mature Osteoclasts (preventing resorption of bone)

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22
Q

What opposes the bone resorptive activity of PTH?

A

OPG

23
Q

The balance of ___ and ____ plays a major role in determining Osteoclast activity and bone resorption

A

OPG and RANKL

24
Q

What maintains calcium and phosphorous homeostasis?

A

by the parathyroid gland

25
Q

How is calcium and phosphate homeostasis maintained?

A
  • Parathyroid Gland secretes PTH in response to low Calcium
    blood levels increasing Calcium levels in serum
  • Then, Negative feedback signals Parathyroid Gland to stop
    PTH release
26
Q

True/False: The body can’t make Calcium, but obtains it from food

A

True

27
Q

Calcium and Phosphate are absorbed by the __________.

A

small intestines

28
Q

Since cations are normally poorly digested name some adaptations that help the absorption of calcium.

A

 Vitamin D promotes Calcium absorption by Intestines

29
Q

True/False: Phosphate is absorbed easily

A

True

30
Q

How much of calcium is excreted vs absorbed?

A

About 35% of ingested Calcium is usually absorbed; rest
is excreted

31
Q

Where is calcium absorbed?

A

the kidneys

32
Q

Normally ______ absorb 99% of filtered calcium)

A

renal tubules

33
Q

What controls the rate of calcium absorption?

A

PTH

34
Q

How is renal phosphate excretion controlled?

A

by an overflow mechanism (when phosphate concentration is < 1 mmol/L, all phosphate is resorbed)

35
Q

_____ can greatly increase phosphate excretion by kidneys.

A

PTH

36
Q

True/False: The body can’t produce its own vitamin C.

A

False

37
Q

How is Vitamin D3 produced?

A

Formed in skin due to irradiation of 7-dehydrocholesterol (substance normally found in skin) by ultraviolet rays from the sun

38
Q

You need exposure to ___ (or Vitamin D from ____, ______)

A

Sun, food, supplements

39
Q

What is Calcitriol?

A

synthetic vitamin D

40
Q

What is Calcitriol used to treat?

A

hypocalcemia and osteoporosis

41
Q

What is known as the sunshine vitamin?

A

Vitamin D3

42
Q

What is the most active for a vitamin D?

A

vitamin D3

43
Q

How does vitamin D3 help the body?

A

by increasing calcium
absorption from intestines
to form hardened bones

44
Q

What happens when plasma concentration of calcium rises?

A
  • PTH is supressed
  • 1,25-dihydroxycholecalciferol is
    also depressed, which decreases
    absorption of calcium from
    Intestines, Bones and Kidney
    (renal tubules)
45
Q

How much calcium do adults need a day?

A

1,000-1,200 milligrams/day

46
Q

Give examples of foods that are calcium-rich.

A

Milk, Yogurt, Hard Cheese (Parmesan, Romano),Cottage
Cheese, Ice Cream, Kefir
- Broccoli (roughly double the amount when cooked)
- Canned seafood (sardines, salmon, shrimp)
- Oranges, Almonds, Almond Milk, Soy Milk, White Beans
- Rhubarb, Canned Tomatoes
- Fortified Waffles, Fortified Orange Juice
- Butternut Squash, Kale, Bok Choy

47
Q

Where is Calcitonin produced?

A

Thyroid (Parafollicular cells)

48
Q

Where does Calcitonin act?

A

Bone

49
Q

What is the structure of Calcitonin?

A

Peptide

50
Q

Is Calcitonin Lipid or Water soluble?

A

Water

51
Q

What does Calcitonin do?

A
  • Opposes effect of PTH (e.g. it decreases plasma calcium)
  • Decreases Osteoclast activity and osteolysis
  • Decreases Osteoclast formation (and subsequent osteoblast)
52
Q

How is calcitonin stimulated?

A

by increased plasma calcium

53
Q

True/False: Calcitonin only has a transient effect on plasma calcium

A

True

54
Q
A

Physiology for Engineers (30 decks)

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