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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
What is the normal value of intrapleural/intrathoracic pressure?
Less than atmospheric pressure
26
What is inspiration?
An active process which depends on muscle contraction
27
What does the diaphragm (major inspiratory muscle) do?
Increases the volume of the thorax vertically by contracting and flattening out its dome shape
28
What nerve supplies the diaphragm?
Phrenic nerve
29
Where does the phrenic nerve emerge from the spinal cord?
Cervical vertebrae 3, 4 and 5
30
What does the external intercostal muscle do?
Contraction lifts the ribs and moves out the sternum
31
What does increase in size of the lungs result in?
Causes the intra-alveolar pressure to fall
32
Why does the increase in size of the lungs cause the intra-alveolar pressure to fall?
Air molecules become contained in a larger volume (Boyle's Law)
33
What is normal expiration?
A passive process brought about by relaxation of inspiratory muscles
34
How do the chest wall and stretched lungs recoil to their preinspiratory size?
Due to their elastic properties
35
How does recoil of the lungs affect intra-alveolar pressure?
Causes intra-alveolar pressure to rise
36
Why does recoil of the lungs cause intra-alveolar pressure to rise?
Air molecules become contained in a smaller volume (Boyle’s Law)
37
What happens to intra-alveolar and intraplueral pressures during inspiration?
Both decrease
38
What happens to intra-alveolar and intraplueral pressures during expiration?
Intrapleural and intra-alveolar pressures increase - however, intrapleural pressure is always sub-atmospheric
39
What is pneumothorax?
Air in the pleural space
40
What are the causes of pneumothorax?
Can be spontaneous, traumatic or iatrogenic
41
What can pneumothorax result in?
Can abolish transmural pressure gradient leading to lung collapse (unable to breathe)
42
Will a small pneumothorax always show symptoms?
No, small pneumorthorax can be asymptomatic
43
What are symptoms of pneumothorax?
Shortness of breath and chest pain
44
What are physical signs of pneumothorax?
* Hyperresonant percussion note | * Decreased/absent breath sounds
45
What 2 factors cause the lungs to recoil during expiration?
* Elastic connective tissue | * Alveolar surface tension - most important
46
What is alveolar surface tension?
Attraction between water molecules at liquid air interface
47
What effect does alveolar surface tension have on the lungs?
In the alveoli this produces a force which resists the stretching of the lungs
48
What reduces alveolar surface tension?
Pulmonary surfactant
49
What is pulmonary surfactant?
A complex mixture of lipids and proteins secreted by type II alveoli
50
How does pulmonary surfactant reduce alveolar surface tension?
By interspersing between the water molecules lining the alveoli
51
What would happen if alveoli were lined with water alone?
The surface tension would be too strong so the alveoli would collapse
52
What is Laplace's Law?
Smaller alveoli (with smaller radius - r) have a higher tendency to collapse
53
What is the equation for LaPlace's Law?
P = 2T/r ``` P = inward directed collapsing pressure T = surface tension r = radius of the alveolus ```
54
Why is it important that surfactant lowers the surface tension of smaller alveoli more than larger alveoli?
Smaller alveoli have a higher tendency to collapse
55
What does surfactant serrated by smaller alveoli prevent?
Prevents the smaller alveoli from collapsing and emptying their air contents into the larger alveoli
56
Why do premature babies often get Respiratory Distress syndrome of the new born?
Developing fetal lungs are unable to synthesize surfactant until late in pregnancy - Premature babies may not have enough pulmonary surfactant
57
What are the effects of respiratory distress syndrome of the new born?
The baby makes very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs
58
What is a factor other than pulmonary surfactant that keeps the alveoli open?
Alveolar interdependence
59
What is alveolar interdependence?
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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