Gas Exchange in Respiration Flashcards

1
Q

what is the tidal volume

A

the volume breathed in and expired.

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2
Q

how do gases move along pressure gradients

A

downward. from high to low

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3
Q

on average, how many ml/min of oxygen are consumed

A

250

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4
Q

on average, how many ml/min of carbon dioxide are expired

A

200

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5
Q

what is the partial pressure of oxygen

A

150mmHg

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6
Q

is partial pressure of oxygen in the blood greater before going into the lungs are after

A

after

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7
Q

what do pressure gradients show

A

the direction of movement of oxygen and carbon dioxide in the respiratory system

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8
Q

what is the partial pressure

A

pressure a gas exerts in a particular environment, taking into account if the environment is wet or dry

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9
Q

what must the sum of partial pressures of a gas be equal to

A

total pressure

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10
Q

what do pressure changes in the environment depend on

A

weather patterns and the time of day

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11
Q

what is barometric pressure

A

the pressure outside the body

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12
Q

what is the equation to calculate partial pressure

A

fraction of the gas in the gas mixture times by the barometric pressure

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13
Q

what is the pressure of water vapour in the body

A

47mmHg

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14
Q

how many ml of air breathed in per breath on average at rest

A

500ml

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15
Q

how many ml of air remains in the airways after expiration

A

150ml

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16
Q

describe the respiratory tree

A

trachea
bronchi
non respiratory bronchioles
respiratory bronchioles
alveolar ducts

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17
Q

what happens at each division of the respiratory tree

A

increase in number, an increase in surface area

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18
Q

do the conducting airways participate in gas exchange

A

no

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19
Q

what are the respiratory airways

A

bronchioles with the alveoli where gas exchange occurs, from the terminal bronchioles to the alveoli

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20
Q

what is a respiratory unit

A

basic physiological unit of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli

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21
Q

how many alveolar sacs in average adult

A

300-400 million

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22
Q

describe alveoli

A

polygonal
type 1 and type 2 epithelial cells

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23
Q

what feature of alveoli encourages gas exchange the most

A

its close connection with capillary networks

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24
Q

describe type 1 epithelial cells in alveoli

A

97% of surface area of alveoli.
primary site of gas exchange

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25
Q

describe type 2 epithelial cells of the alveoli

A

septal cells
3% surface area
produce pulmonary surfactant (this reduces surface tension)

alveolar macrophages remove debris

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26
Q

describe the key features of alveolar

A

large surface area of 100m2
very thin walls
good diffusion characteristics

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27
Q

what are the blood supplies of the lungs

A

pulmonary circulation
bronchial circulation

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28
Q

describe pulmonary circulation

A

brings deoxygenated blood from the heart to lung and oxygenated blood from lungs to the heart and then the rest of the body

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29
Q

describe bronchial circulation

A

brings oxygenated blood to the lung parenchyma

30
Q

function of the lymphatic system

A

defence and removal of lymph fluid

31
Q

what is the total blood volume in pulmonary circulation

A

500ml

32
Q

how many ml of blood in the alveolar capillary network at rest

A

75ml

33
Q

what is the blood volume in the alveolar capillary network during exercise and how does this happen

A

increases from 75 to 200.
recruitment of new capillaries secondary to an increase in pressure and flow

34
Q

describe arteries

A

thin walled
highly compliant
large diameter
low resistance

35
Q

how does gas exchange occur

A

dense mesh like network of capillaries and alveoli

36
Q

how many seconds for blood cells to pass through capillaries

A

one second

37
Q

describe the gas gradient of pulmonary circulation

A

oxygen enters
carbon dioxide leaves

38
Q

describe the gas gradients of systemic circulation

A

oxygen leaves blood
carbon dioxide enters blood

39
Q

what are gas concentration gradients important for

A

direction of flow

40
Q

do blood and air have a close contact

A

yes

41
Q

how do the volumes of carbon dioxide and oxygen that move each minute differ

A

they are similar

42
Q

is the pressure gradient of oxygen lesser or greater than carbon dioxide

A

greater

43
Q

is carbon dioxide or oxygen more diffusable

A

carbon dioxide

44
Q

describe volume and pressure of pulmonary circulation

A

large volumes at low pressure

45
Q

what is ventilation

A

process by which air moves in and out of the lung

46
Q

what is perfusion

A

process by which deoxygenated blood passes through the lung and becomes oxygenated

47
Q

what is the level of partial pressure in oxygen and carbon dioxide related to

A

the relationship between ventilation and perfusion

48
Q

what is the V/Q ratio

A

the relationship between ventilation and perfusion

49
Q

describe the distribution of ventilation

A

not uniform due to gravity

50
Q

describe ventilation in the upright position

A

alveoli in the apex is more expanded than at the base

51
Q

describe graviy’s impact on ventilation distribution in the lungs

A

gravity pulls the lung down and away from the chest wall
pleural pressure is more negative at the apex than at the base
transpulmonary pressure is greater at the apex than at the base
increased alveolar volume in the apex

52
Q

what is compliance

A

this refers to how much effort is required to stretch the lungs and chest wall

53
Q

what does high compliance mean for breathing

A

it means that the lungs and the chest wall expand easily

54
Q

what is resistance

A

narrowing or obstruction of airways
reduced lumen
increased resistance that can lead to decreased ventilation

55
Q

what does decreased compliance mean for breathing

A

common feature when there are pulmonary conditions, leads to:
- scarring in the lung tissue (like in TB)
- lung filled with fluid (edema)
- deficiency in surfactant production
- destruction of elastic fibres (emphysema)

56
Q

what is an increased resistance a common feature in

A

pulmonary conditions

57
Q

what can increased resistance lead to

A
  • asthma
  • COPD due to obstruction or collapse of airways
58
Q

is pulmonary influenced more or less by gravity compared to systemic circulation

A

more

59
Q

describe upright pulmonary blood flow

A

there is greater blood flow the base than the apex

60
Q

describe pulmonary circulation

A

low pressure and low resistance

61
Q

what defines the V/Q ratio of a single alveolus

A

alveolar ventilation divided by capillary flow

62
Q

what defines the V/Q ratio of the lung

A

total alveolar ventilation divided by cardiac output

63
Q

what is the average alveolar ventilation of healthy individuals

A

4-6 litres per minute

64
Q

what is the pulmonary blood flow on average in healthy individuals

A

5 litres per minute

65
Q

what is the V/Q for a lung in a healthy individual

A

0.8 to 1.2

66
Q

what is the V/Q ratio when the ventilation exceeds the perfusion

A

greater than one

67
Q

what is the V/Q ratio when perfusion exceeds ventilation

A

less than one

68
Q

what does V/Q mismatching lead to

A

arterial hypoxemia in patients with respiratory disorders

69
Q

what is the V/Q ratio a ratio of

A

ventilation to blood flow

70
Q

what does it mean if V/Q ratio is 1

A

this is the perfect model, where the inspired gas and cardiac output partial pressures are shared equally

71
Q

what does V/Q mismatching result in

A

varying alveolar and capillary gas contents

72
Q

what are the regional differences in ventilation and perfusion largely down to

A

gravity