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Respiratory: Physiology > Respiratory Mechanics 1 > Flashcards

Respiratory Mechanics 1 Flashcards

1
Q

Why do cells need a constant supply of oxygen?

A

To produce energy and function

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2
Q

What must happen to the CO2 produced by cellular reactions in the body?

A

It must be continuously removed from the body

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3
Q

What is internal respiration?

A

The intracellular mechanisms which consume O2 and produce CO2

Glucose + energy —> ATP + CO2

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4
Q

What is external respiration?

A

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

What are the 4 steps of external respiration?

A
  • Ventilation
  • Gas exchange between alveoli and blood
  • Gas transport in the blood
  • Gas exchange at the tissue level
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6
Q

What is Ventilation?

A

The mechanical process of moving air between the

atmosphere and alveolar sacs

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7
Q

What is Gas Exchange between Alveoli and Blood?

A

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

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8
Q

What is Gas Transport in the Blood?

A

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

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9
Q

What is Gas Exchange at Tissue Level?

A

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

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10
Q

What are the 4 body systems involved in external respiration?

A
  • The respiratory system
  • The Cardiovascular system (pumps blood)
  • The haematology system (carries O2 and CO2)
  • The nervous system (breathing)
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11
Q

In which direction does air flow?

A

Down pressure gradient from a region of high pressure to a region of low pressure

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12
Q

What must happen in order for air to flow into the lungs during inspiration?

A

The intra-alveolar pressure must become less than atmospheric pressure (pressure gradient)

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13
Q

How is intra-alveolar pressure made less than atmospheric pressure if before inspiration, intra-alveolar pressure is equivalent to atmospheric pressure?

A

During inspiration, thorax and lungs expand due to contraction of inspiratory muscles
Increased volume = less pressure

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14
Q

What is Boyle’s Law?

A

At any constant temperature the
pressure exerted by a gas varies inversely with the volume of the gas

i.e. as the volume of a gas increases the pressure exerted by the gas decreases

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15
Q

How does the movement of the chest wall expand the lungs if there is no physical connections between the lungs and chest wall?

A
  • Intrapleural fluid cohesiveness
  • Negative intrapleural pressure

Hold thoracic wall and lungs in close apposition

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16
Q

What 2 forces hold the thoracic Walland the lungs in close apposition?

A
  • Intrapleural fluid cohesiveness

* Negative intrapleural pressure

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17
Q

What is the intrapleural fluid cohesiveness?

A

The water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart - so the pleural membranes (visceral and parietal) stick together

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18
Q

What is the negative intrapleural pressure?

A

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

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19
Q

What 3 pressures are important in ventilation?

A
  • Atmospheric pressure
  • Intra-alveolar (intrapulmonary) pressure
  • Intrapleural (intrathoracic) pressure
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20
Q

What is atmospheric pressure?

A

Pressure caused by the weight of the gas in thermosphere on the Earth’s surface

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21
Q

What is the normal value of atmospheric pressure?

A

760 mm Hg (101 kPa) at sea level

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22
Q

What is intra-alveolar/intrapulmonary pressure?

A

Pressure within the lung alveoli

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23
Q

What is the normal value of intra-alveolar/intrapulmonary pressure?

A

760 mm Hg (101 kPa) when equilibrated with atmospheric pressure

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24
Q

What is intraplueral/intrathoracic pressure?

A

Pressure exerted outside the lungs within the pleural cavity

25
Q

What is the normal value of intrapleural/intrathoracic pressure?

A

Less than atmospheric pressure

26
Q

What is inspiration?

A

An active process which depends on muscle contraction

27
Q

What does the diaphragm (major inspiratory muscle) do?

A

Increases the volume of the thorax vertically by contracting and flattening out its dome shape

28
Q

What nerve supplies the diaphragm?

A

Phrenic nerve

29
Q

Where does the phrenic nerve emerge from the spinal cord?

A

Cervical vertebrae 3, 4 and 5

30
Q

What does the external intercostal muscle do?

A

Contraction lifts the ribs and moves out the sternum

31
Q

What does increase in size of the lungs result in?

A

Causes the intra-alveolar pressure to fall

32
Q

Why does the increase in size of the lungs cause the intra-alveolar pressure to fall?

A

Air molecules become contained in a larger volume (Boyle’s Law)

33
Q

What is normal expiration?

A

A passive process brought about by relaxation of inspiratory muscles

34
Q

How do the chest wall and stretched lungs recoil to their preinspiratory size?

A

Due to their elastic properties

35
Q

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

A

Causes intra-alveolar pressure to rise

36
Q

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

A

Air molecules become contained in a smaller volume (Boyle’s Law)

37
Q

What happens to intra-alveolar and intraplueral pressures during inspiration?

A

Both decrease

38
Q

What happens to intra-alveolar and intraplueral pressures during expiration?

A

Intrapleural and intra-alveolar pressures increase - however, intrapleural pressure is always sub-atmospheric

39
Q

What is pneumothorax?

A

Air in the pleural space

40
Q

What are the causes of pneumothorax?

A

Can be spontaneous, traumatic or iatrogenic

41
Q

What can pneumothorax result in?

A

Can abolish transmural pressure gradient leading to lung collapse (unable to breathe)

42
Q

Will a small pneumothorax always show symptoms?

A

No, small pneumorthorax can be asymptomatic

43
Q

What are symptoms of pneumothorax?

A

Shortness of breath and chest pain

44
Q

What are physical signs of pneumothorax?

A
  • Hyperresonant percussion note

* Decreased/absent breath sounds

45
Q

What 2 factors cause the lungs to recoil during expiration?

A
  • Elastic connective tissue

* Alveolar surface tension - most important

46
Q

What is alveolar surface tension?

A

Attraction between water molecules at liquid air interface

47
Q

What effect does alveolar surface tension have on the lungs?

A

In the alveoli this produces a force which resists the stretching of the lungs

48
Q

What reduces alveolar surface tension?

A

Pulmonary surfactant

49
Q

What is pulmonary surfactant?

A

A complex mixture of lipids and proteins secreted by type II alveoli

50
Q

How does pulmonary surfactant reduce alveolar surface tension?

A

By interspersing between the water molecules lining the alveoli

51
Q

What would happen if alveoli were lined with water alone?

A

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

52
Q

What is Laplace’s Law?

A

Smaller alveoli (with smaller radius - r) have a higher tendency to collapse

53
Q

What is the equation for LaPlace’s Law?

A

P = 2T/r

P = inward directed collapsing pressure 
T = surface tension 
r = radius of the alveolus
54
Q

Why is it important that surfactant lowers the surface tension of smaller alveoli more than larger alveoli?

A

Smaller alveoli have a higher tendency to collapse

55
Q

What does surfactant serrated by smaller alveoli prevent?

A

Prevents the smaller alveoli from collapsing and emptying their air contents into the larger alveoli

56
Q

Why do premature babies often get Respiratory Distress syndrome of the new born?

A

Developing fetal lungs are unable to synthesize surfactant until late in pregnancy - Premature babies may not have enough pulmonary surfactant

57
Q

What are the effects of respiratory distress syndrome of the new born?

A

The baby makes very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs

58
Q

What is a factor other than pulmonary surfactant that keeps the alveoli open?

A

Alveolar interdependence

59
Q

What is alveolar interdependence?

A

If an alveolus start to collapse the surrounding alveoli stretch and then recoil exerting expanding forces in the
collapsing alveolus to open it

Respiratory: Physiology (6 decks)

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