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Respiratory - Physiology > Physiology L1 - Overview of Respiration and Respiratory Mechanics > Flashcards

Physiology L1 - Overview of Respiration and Respiratory Mechanics Flashcards

1
Q

What does internal respiration refer to?

A

It refers to the intracellular mechanisms which consumes O2 and produces CO2

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2
Q

Why must CO2 be continuously removed?

A

Build up of CO2 is toxic

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3
Q

Why do cells need a constant supply of O2?

A

To produce energy to function

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4
Q

What does external respiration refer to?

A

It refers to the sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body

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5
Q

How many steps does external respiration have?

A

4

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6
Q

What are the fours steps of external respiration?

A
  1. Ventilation
  2. Gas exchange between alveoli and blood
  3. Gas transport in the blood
  4. Gas exchange at the tissue level
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7
Q

Describe ventilation?

A

The first step in external respiration.

It’s the mechanical process of moving gas in and out of the lungs/the gas exchange between the atmosphere and air sacs (alveoli) in the lungs

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8
Q

Describe gas exchange between alveoli and blood occur?

A

The seconds step in external respiration.

It is the exchange of O2 and CO2 between the air in the alveoli and the blood in the pulmonary capillaries

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9
Q

Describe gas transport in the blood?

A

The third step in external respiration.

Its the binding and transport of O2 and CO2 in the circulating blood

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10
Q

Describe gas exchange at the tissue level?

A

The fourth and final step of external respiration.

Its the exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells

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11
Q

External respiration is a multi-system process. What main three systems need to be functioning properly to supply the body with sufficient O2 and removal of CO2 (external respiration)?

A
  1. The respiratory system
  2. The cardiovascular system
  3. The haematological system
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12
Q

What law causes air to flow down a pressure gradient from a region of high pressure to a region of low pressure?

A

Boyle’s Law

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13
Q

Describe Boyle’s Law?

A

At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas (P1V1 = P2V2)

As the volume of gas increases the pressure exerted by the gas decreases

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14
Q

During ventilation do the intra-alveoli need low or high pressure?

A

Low (in relation to atmospheric pressure)

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15
Q

During ventilation does atmospheric pressure need to be low or high?

A

High (in relation to the intra-alveoli pressure)

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16
Q

What is the pressure in the intra-alveoli before inspiration equivalent to?

A

Atmospheric pressure

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17
Q

What cause the thorax and lungs to expand during inspiration?

A

The contraction of inspiratory muscles

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18
Q

What causes gas to flow from atmosphere into the alveoli?

A

The increase in the volume of the alveoli (lungs) creates a lower pressure than the atmospheric pressure (according to Boyle’s Law)

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19
Q

What two forces link the lungs to the thorax in close opposition?

A
  1. The intrapleural fluid cohesiveness

2. The negative intrapleural pressure

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20
Q

Describe intrapleural fluid cohesiveness?

A

The water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Hence the pleural membranes tend to stick together.

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21
Q

Describe negative intrapleural pressure?

A

The sub-atmospheric intrapleural pressure create a transmural pressure gradient across the lung wall and across the chest wall. So the lungs are forced to expand outwards while the chest is forced to squeeze inwards.

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22
Q

What is the intra-alveolar pressure and in which direction does it push?

A

It exerts a pressure o 760mmHg outward

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23
Q

What is the intrapleural pressure (pressure in the pleural cavity) and in which direction does it push across the lung wall?

A

It exerts a pressure of 756mmHg inwards

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24
Q

What is the transmural pressure gradient across the lung?

A

Its the intra-alveolar pressure minus the intrapleural pressure (760 - 756 = 4mmHg)

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25
Q

What is the transmural pressure gradient across thoracic wall?

A

Its the atmospheric pressure minus the intrapleural pressure (760 - 756 = 4mmHg)

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26
Q

What is the effect of the transmural pressure gradient?

A

It pushes out on the lungs, stretching them to fill the larger thoracic cavity

27
Q

What is the intrapleural pressure (pressure in the pleural cavity) and in which direction does it push across the thoracic wall?

A

It exerts a pressure of 756mmHg outwards

28
Q

What is the atmospheric pressure and in which direction does it push across the thoracic wall?

A

It exerts a pressure of 760mmHg inwards

29
Q

What are the three important pressure in ventilation?

A
  1. Atmospheric pressure
  2. Intra-alveolar pressure
  3. Intrapleural pressure
30
Q

Describe atmospheric pressure?

A

The pressure exerted by the weight of the gas in the atmosphere on objects on the Earths (760mmHg)

31
Q

Describe intra-alveolar pressure?

A

The pressure within the alveoli (760mmHg)

32
Q

Describe intrapleural pressure?

A

The pressure within the pleural sac.

The pressure exerted outside the lungs within the thoracic cavity usually less that atmospheric (756mmHg)

33
Q

Is inspiration active or passive?

A

Active (depends on muscle contraction)

34
Q

What major inspiratory muscle contracts to increase the volume of the thorax vertically?

A

Diaphragm

35
Q

What nerves supply the diaphragm?

A

C3, 4 and 5. ( C3, 4 and 5 keep the diaphragm alive!)

36
Q

How does the diaphragm change shape during inspiration?

A

The dome shape flattens out to increase the volume of the thorax vertically

37
Q

What muscles contract to lift the ribs and move out the sternum (the “bucket handle” mechanism)?

A

External intercostal muscles

38
Q

What are the two main inspiratory muscles?

A
  1. Diaphragm

2. External intercostal muscles

39
Q

What does the increase in the size of the lungs during inspiration cause?

A

The intra-alveolar pressure to fall

40
Q

What does the fall in intra-alveolar pressure during inspiration cause?

A

Air enters the lungs down its pressure gradients until the intra-alveolar pressure become equal to atmospheric pressure

41
Q

Is normal expiration active or passive?

A

Passive (relaxation of inspiratory muscles)

42
Q

What happens during expiration?

A

The inspiratory muscles relax. The chest wall and stretched lungs recoil to their preinspiratory size because of their elastic properties

43
Q

How does the recoil of the lungs affects the intra-alveolar pressure?

A

It rises!

44
Q

Why does the recoil of the lungs cause the intra-alveolar pressure rise?

A

The air molecules are contained in a smaller volume and due to Boyle’s Law the pressure rises (smaller alveoli)

45
Q

What does the rise in intra-alveolar pressure during expiration cause?

A

The air leaves the lungs down its pressure gradient until the intra-alveolar pressure becomes equal to the atmospheric pressure

46
Q

In general terms what happens to the intrapleural pressure during the respiratory cycle?

A

The pressure tends to fall during inspiration and rise during expiration

47
Q

What is a pneumothorax?

A

Causes collapsed lung due to air in the pleural space which abolishes the transmural pressure gradient

48
Q

What are the two types of pneumothorax?

A
  1. Traumatic pneumothorax

2. Spontaneous pneumothorax

49
Q

Describe traumatic pneumothorax?

A

A puncture in the chest wall permits air from the atmosphere to flow down its pressure gradient and enter the pleural cavity, abolishing the transmural pressure gradient.

50
Q

Describe spontaneous pneumothorax?

A

A hole in the lung wall permits air to move down its pressure gradient and enter the pleural cavity from the lungs, abolishing the transmural pressure gradient. As with traumatic pneumothorax, the lung collapses to its unstretched size.

51
Q

What is a collapsed lung?

A

When the transmural pressure gradient is abolished, the lung collapses to its unstretched size, and the chest wall springs outward.

52
Q

What causes the lungs to recoil during expiration?

A
  1. Elastic connective tissue

2. Alveolar surface tension

53
Q

Describe the effects elastic connective tissue in regards to recoil of the lungs during expiration?

A

Elastic connective tissue in the lungs causes the whole structure to bounce back into shape

54
Q

Describe the effects of alveolar surface tension in regards to recoil of the lungs during expiration?

A

Attraction between water molecules at the liquid air interface produces a force which resists the stretching of the lungs.

55
Q

What would happen if alveoli were lined with water alone?

A

The surface tension would be too strong so the alveoli would collapse

56
Q

Why do smaller alveoli have a higher tendency to collapse?

A

According to LaPlace’s law the smaller the radius of the alveoli the higher tendency of collapsing

57
Q

What is pulmonary surfactant?

A

Complex mixture of lipids and proteins secreted by type II alveoli

58
Q

What does pulmonary surfactant do?

A

It lowers alveolar surface tension by interspersing between the water molecules lining the alveoli. This prevent the smaller alveoli from collapsing and emptying their air contents into the larger alveoli

59
Q

What type of alveoli (small or large) have more surfactant?

A

Surfactant lowers the surface tension of smaller alveoli more than that of large alveoli

60
Q

What is respiratory distress syndrome of new borns?

A

When premature babies do not have enough pulmonary surfactant. The baby makes very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs

61
Q

What causes respiratory distress syndrome of new borns?

A

Developing fetal lungs are unable to synthesize surfactant until late in pregnancy and the baby is born prematurely

62
Q

What is the alveolar interdependence?

A

A factor which helps keep the alveoli open. If an alveolus start to collapse the surrounding alveoli are
stretched and then recoil exerting expanding forces in the
collapsing alveolus to open it

63
Q

Name the forces keeping the alveoli open?

A
  1. Transmural pressure gradient
  2. Pulmonary surfactant (which opposes alveolar surface tension)
  3. Alveolar interdependence
64
Q

Name the forces promoting alveolar collapse?

A
  1. Elasticity of stretched pulmonary connective tissue fibres
  2. Alveolar surface tention

Respiratory - Physiology (3 decks)

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