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Respiratory system > Pulmonary ventilation mechanics > Flashcards

Pulmonary ventilation mechanics Flashcards

1
Q

What is pulmonary ventilation?

A

The flow of air into and out of the lung alveoli from the atmosphere

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2
Q

What is inspiration?

A

Breathing in

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3
Q

What is tidal inspiration?

A

Breathing in at rest

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4
Q

What muscular activities occur during tidal inspiration?

A

Diaphragm contracts

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5
Q

What happens to the diaphragm when it contracts?

A

It moves downwards and flattens

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6
Q

What happens to the lungs themselves when the diaphragm contracts?

A

Diaphragm pulls lower surfaces of lungs downwards

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7
Q

What happens to the volume and pressure of the lungs when their lower surfaces are pulled downwards?

A

Volume of lungs increases

Pressure of lungs decreases below atmospheric pressure

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8
Q

How does the pressure decrease in the lungs affect the flow of air between the lungs and the atmosphere during inspiration?

A

Air moves from higher atmospheric pressure into the lungs, which are at a lower pressure
down the pressure gradient

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9
Q

What additional muscular activities occur during forced inspiration?

A

External intercostal muscles contract

Sternocleidomastoid, scalene and pectoralis muscles contract

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10
Q

How do the sternocleidomastoid, pectoralis and scalene muscles act to move the ribs?

A

Their other attachment is stabilised

so when they contract, they act on their attachment to the ribs and move the ribs

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11
Q

What happens to the ribs when the external intercostal, scalene and pectoralis muscles contract?

A

They move upwards and outwards

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12
Q

What happens to the sternum and ribs when the sternocleidomastoid muscle contracts? How?

A

Sternum moves anteriorly and superiorly by pull of sternocleidomastoid

Ribs moves upwards and outwards by pull of sternum

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13
Q

What happens to the lungs themselves when the external intercostal, sternocleidomastoid, scalene and pectoralis muscles contract?

A

Chest wall pulls anterior and lateral surfaces of lungs upwards and outwards

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14
Q

Why do the lungs move upwards and outwards as the chest wall does so?

A

Because the lungs are attached to the chest wall by the pleura

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15
Q

What is expiration?

A

Breathing out

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16
Q

What is tidal expiration?

A

Breathing out at rest

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17
Q

What muscular activities occur during tidal expiration?

A

Diaphragm relaxes

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18
Q

What happens to the diaphragm when it relaxes?

A

It moves upwards and resumes its normal dome-shape

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19
Q

What happens to the lungs themselves when the diaphragm relaxes?

A

Lower surfaces of lungs are no longer pulled downwards

elastic recoil of lungs moves them back up

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20
Q

What happens to the volume and pressure of the lungs when the lungs recoil?

A

Volume of lungs decreases

Pressure of lungs increases above atmospheric pressure

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21
Q

How does the increase in pressure in the lungs affect air flow between the lungs and atmosphere during expiration?

A

Air moves from the higher pressure in the lungs to the lower pressure in the atmosphere
down the pressure gradient

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22
Q

What additional muscular activities during forced expiration?

A

External intercostal muscles relax

Internal intercostal and abdominal muscles contract

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23
Q

What happens to the ribs when the external intercostal muscles relax and the internal intercostal muscles contract?

A

Ribs move downwards and inwards

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24
Q

What happens to the lungs themselves when the external intercostals muscles relax and the internal intercostal muscles contract?

A

Chest wall no longer pulls anterior and lateral surfaces of lungs upwards and outwards
elastic recoil of lungs moves them back down and in

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25
Q

What happens to the lungs themselves when the abdominal muscles contract?

A

Abdominal muscles push contents of abdomen upwards
push diaphragm upwards
compress the lungs upwards

26
Q

What are the pressures in the pleural space?

A

Inspiration = -7mmHg

Expiration = -3mmHg

27
Q

Why is the pressure in the pleural space negative?

A

Because the parietal pleura and visceral pleura are pulled in opposite directions

28
Q

What direction is the parietal pleura pulled in? How?

A

Outwards by the chest wall wanting to spring outwards

29
Q

What direction is the visceral pleura pulled in? How?

A

Inwards by the elastic recoil of the lungs

30
Q

Why does the pressure in the pleural space become more negative with inspiration?

A

Chest wall moves upwards and outwards
pulls on parietal pleura even more
increases volume of space in pleural space, decreasing pressure

31
Q

What is meant by compliance?

A

The ability of the lungs to distend

32
Q

What is the equation for compliance?

A

Change in lung volume
____________________
Change in pleural pressure

33
Q

What volume and pressure changes occurs in lungs with low compliance?

A

Low compliance means need bigger decreases in pleural pressure
to pull the lungs
and increase their volume

34
Q

What volume and pressure changes occur in lungs with high compliance?

A

High compliance means need smaller decreases in pleural pressure
to pull the lungs
and increase their volume

35
Q

What are the factors affecting compliance of the lungs?

A

Elastic recoil

Fibrosis

36
Q

How does elastic recoil of lungs affect lung compliance?

A

Need bigger decreases in pleural pressure to pull the lungs and increase their volume
therefore decreases lung compliance

37
Q

What causes the elastic recoil of the lungs?

A

Elastin fibers in the lung tissue

Surface tension

38
Q

What is the biggest cause of elastic recoil of the lungs?

A

Surface tension

39
Q

How does elastin in the lungs change with age?

A

Decrease in amount of elastin

40
Q

What is Laplace’s law?

A

Pressure = 2 x surface tension / radius

Pressure generated by the alveolar elastic recoil

41
Q

What is surface tension?

A

When water is in contact with air
the water molecules at the surface are strongly bonded to each other
they attempt to move closer to each other to minimise the surface area

42
Q

Where does surface tension occur in the lungs?

A

Alveoli

43
Q

How does surface tension occur in the alveoli?

A

Water on inner surface of alveoli

44
Q

What are the effects of surface tension in the alveoli?

A

Makes the alveoli collapse

smaller ones into larger ones

45
Q

Why would smaller alveoli collapse into larger alveoli, as opposed to them evening out?

A

Smaller alveoli have smaller radius than larger ones
therefore have higher pressure than larger ones
air moves from higher pressure to lower pressure down the pressure gradient

46
Q

What does surfactant stand for?

A

Surface active agent

47
Q

What is surfactant made up of?

A

Complex mixture of lipids and proteins

48
Q

Where is surfactant found in the lungs?

A

Alveoli

49
Q

What is responsible for the surfactant found in the alveoli?

A

Type 2 pneumocytes

50
Q

When does surfactant production in the alveoli begin?

A

25-28 weeks of gestational age

51
Q

When is the amount of surfactant in the alveoli sufficient?

A

35 weeks of gestational age

52
Q

What is the effect of surfactant on surface tension?

A

Decreases surface tension

53
Q

How does surfactant decrease surface tension?

A

Surfactant spreads over inner surface of alvoeli

separates the water molecules at the surface from each other

54
Q

How does surfactant affect the alveoli?

A

Prevents the smaller ones from collapsing into the larger ones

55
Q

How does surfactant prevent smaller alveoli from collapsing into larger alveoli?

A

Surfactant molecules spread over inner surface of larger alveoli more thinly, less effective
surface tension decreases less
pressure decreases less
equivalent to that of smaller alveoli

56
Q

How does surfactant affect lung compliance?

A

Reduces elastic recoil of lungs
need smaller decreases in pleural pressure to pull the lungs and increase their volume
therefore increases lung compliance

57
Q

What is the cause of respiratory distress syndrome of the newborn?

A

Babies born prematurely before 30 weeks

have less surfactant in their alveoli, increased surface tension, alveolar collapse

58
Q

What are the signs of respiratory distress syndrome of the newborn?

A

Intercostal and subcostal recession

59
Q

Why is intercostal and subcostal recession seen with respiratory distress syndrome of the newborn?

A

Reduced pressure in the lungs

draws overlying attached muscles and skin inwards

60
Q

How is respiratory distress syndrome of the newborn treated?

A

Surfactant replacement

Oxygen

Assisted ventilation

If yet unborn, give glucocorticoid treatment to mother because it increases surfactant production in the foetus

Respiratory system (32 decks)

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