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respiratory lectures > lung physiology 1 > Flashcards

lung physiology 1 Flashcards

1
Q

what is the respiratory pump

A

consists of abdominal and thoracic structures that are important in the expansion and contraction of the lungs

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2
Q

where is the respiratory pump

A

between the head and abdomen

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3
Q

define venous return

A

the return of blood to the right side of the heart via the vena cava

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4
Q

what does respiratory pump do

A

when muscles contract and relax during the inspiration and expiration process,
pressure changes occur in the thoracic and abdominal cavities.

these pressure changes compress the nearby veins and assist blood return to the heart

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5
Q

what are the 2 muscles of respiration

A

inspiration

expiration

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6
Q

what do inspiratory muscles do

A

expand the thoracic cavity

help in inhalation

due to diaphragm and external intercostal muscles contracting

largely quiet

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7
Q

what do expiratory muscles do

A

compress the thoracic cavity

induce exhalation

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8
Q

what are the primary inspiratory muscles

A

diaphragm

external intercostals

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9
Q

is expiration passive or active and why

A

passive during quiet breathing

because of the elastic recoil of the lungs and surface tension

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10
Q

which muscles are involved in expiration

A

internal intercostals

intercostalis intimi

subcostals

abdominal muscles.

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11
Q

what do inspiration muscles do to the the ribs and sternum

A

elevate them

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12
Q

what do expiration muscles do to the ribs and sternum

A

depress them

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13
Q

describe inspiration process

A
  1. phrenic nerve stimulated
  2. diaphragm contracts - flattens, extending the superior/inferior dimension of the thoracic cavity
  3. external intercostal muscles contract - elevates the ribs and sternum, extending the anterior/posterior dimension of the thoracic cavity
  4. results in an increase in the volume of the thoracic cavity
  5. as the lungs are held against the inner thoracic wall by the pleural seal, they also undergo an increase in volume
  6. results in a decrease in the pressure within the lungs.
  7. pressure of the environment external to the lungs is now greater than the environment within the lungs
  8. air moves into the lungs down the pressure gradient
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14
Q

innervation of diaphragm

A

phrenic nerves (C3-C5)

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15
Q

is inspiration active or passive

A

active

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16
Q

what happens during breathing

A

the contraction and relaxation of muscles change the volume of the thoracic cavity.

as the thoracic cavity and lungs move together, this changes the volume of the lungs

in turn changing the pressure inside the lungs

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17
Q

what is inspiration

A

the phase of ventilation in which air enters the lungs.

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18
Q

what is expiration

A

the phase of ventilation in which air is expelled from the lungs.

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19
Q

what is inspiration initaited by

A

by contraction of the inspiratory muscles - diaphragm & external intercostal muscles

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20
Q

what is expiration initiated by

A

by relaxation of the inspiratory muscles

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21
Q

process of expiration

A
  1. diaphragm relaxes to return to its resting position - reducing the superior/inferior dimension of the thoracic cavity
  2. external intercostal muscles relax to depress the ribs and sternum - reducing the anterior/posterior dimension of the thoracic cavity
  3. results in a decrease in the volume of the thoracic cavity
  4. the elastic recoil of the previously expanded lung tissue allows them to return to their original size.
  5. results in an increase in the pressure within the lungs
  6. pressure inside the lungs is now greater than in the external environment
  7. air moves out of the lungs down the pressure gradient.
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22
Q

what is the pleural space

A

the space between the outer surface of the lungs and inner thoracic wall - usually filled with pleural fluid

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23
Q

what does pleural fluid do

A

forms a seal which holds the lungs against the thoracic wall by the force of surface tension.

this seal ensures that when the thoracic cavity expands or reduces, the lungs undergo expansion or reduction in size accordingly.

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24
Q

what are the layers of pleura

A

includes two thin layers of tissue that protect and cushion the lungs

inner layer - visceral pleura

outer layer - parietal pleura

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25
Q

where is visceral pleura

A

wraps around the lungs and is stuck so tightly to the lungs that it cannot be peeled off

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26
Q

where is parietal pleura

A

lines the inside of the chest wall

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27
Q

what is forced breathing/expiration

A

an active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume. It most commonly occurs during exercise.

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28
Q

what are accessory muscles

A

muscles other than the diaphragm and intercostal muscles that may be used for breathing

all of these muscles act to increase the volume of the thoracic cavity

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29
Q

what are the accessory muscles involved in active inspiration (5)

A

Scalenes- elevates the upper ribs.

Sternocleidomastoid - elevates the sternum.

Pectoralis major and minor- pulls ribs outwards.

Serratus anterior - levates the ribs (when the scapulae are fixed).

Latissimus dorsi- elevates the lower ribs.

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30
Q

what do scalenes do

A

elevates the upper ribs

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31
Q

what does sternocleidomastoid do

A

elevates the sternum

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32
Q

what do pectoralis major and minor do

A

pull the ribs outwards

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33
Q

what do serratus anterior do

A

elevates the ribs
(when the scapulae are fixed)

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34
Q

what does latissimus dorsi do

A

elevates the lower ribs

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35
Q

what is active inspiration

A

involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals). All of these muscles act to increase the volume of the thoracic cavity

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36
Q

what is active expiration

A

utilises the contraction of several thoracic and abdominal muscles. These muscles act to decrease the volume of the thoracic cavity

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37
Q

which muscles are involved in active expiration

A

anterolateral abdominal wall

Internal intercostal

Innermost intercostal

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38
Q

what do anterolateral abdominal wall muscles do

A

increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity

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39
Q

what do internal intercostal muscles do

A

depresses the ribs.

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40
Q

what do Innermost intercostal do

A

depresses the ribs

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41
Q

what determines airway resistance

A

tube length

tube radius

flow type

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42
Q

what is gas exchange

A

the process by which oxygen and carbon dioxide move between the bloodstream and the lungs.

this is the primary function of the respiratory system.

it is essential to ensure a constant supply of oxygen to tissues, as well as removing carbon dioxide to prevent its accumulation

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43
Q

define ventilation

A

flow of air into and out of the alveoli

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44
Q

define perfusion

A

total volume of blood reaching the pulmonary capillaries in a given time period

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45
Q

what is V/Q mismatch

ventilation/perfusion

A

when blood is going to poorly ventilated parts of lung

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46
Q

what is dead space

A

volume of air not contributing to ventilation

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47
Q

what affects rate of diffusion of gases (3)

A
  1. concentration gradient: The greater the gradient, the faster the rate
  2. surface area for diffusion: The greater the surface area, the faster the rate
  3. length of the diffusion pathway: The greater the length of the pathway, the slower the rate
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48
Q

what is the sensory nerve supply to the diaphragm

A

phrenic nerve to central tendon and lower 6 or 7 intercostal nerve to peripheral parts.[8]

49
Q

what are the 7 layers of gas exchange

A
  1. alveolar epithelium
  2. tissue interstitium
  3. capillary endothelium
  4. plasma layer
  5. red cell membrane
  6. red cell cytoplasm
  7. Hb binding
50
Q

what are homeostatic responses to V/Q mismatch

A

to divert blood away from poorly ventilated areas (HPVC)

or

divert to better perfused lung areas (LBC)

51
Q

what are homeostatic responses to V/Q mismatch

A

to divert blood away from poorly ventilated areas (HPVC)

or

divert to better perfused lung areas (LBC)

52
Q

why is it important to have matching ventilation and perfusion of the lungs

A

it ensures continuous delivery of oxygen and removal of carbon dioxide from the body

53
Q

define ventilation rate

A

refers to the volume of gas inhaled and exhaled from the lungs in a given time period, usually a minute

54
Q

define ventilation rate

A

refers to the volume of gas inhaled and exhaled from the lungs in a given time period, usually a minute

55
Q

what is the ideal V/Q ratio

A

1 for maximally efficient pulmonary function

however, the ratio varies depending on the part of the lung concerned

56
Q

why are there different V/Q ratios for different areas of the lungs

A

due to the relation of the area to the heart.

areas of lung below the heart have increased perfusion relative to ventilation due to gravity, reducing the V/Q ratio.

as such the overall value in the average human lung is closer to 0.8.

57
Q

how does gravity triggers changes in ventilation and perfusion

A
  1. pleural pressure
  2. hydrostatic pressure
58
Q

effect of pleural pressure on ventilation

A

is increased at the base of the lungs, resulting in more compliant alveoli and increased ventilation

59
Q

effect of hydrostatic pressure on perfusion

A

is decreased at the apex of the lung, resulting in decreased flow and decreased perfusion

60
Q

what happens when ventilation is good but perfusion is poor

A

V/Q value increases

dead space

leads to embolism (pulmonary)
(blood clot)

61
Q

what happens when perfusion is good but ventilation is poor

A

V/Q value decreases

shunt

leads to pulmonary oedema
(collapsed alveoli due to fluid build up)

62
Q

homeostatic response for when ventilation is good but perfusion is poor

A

local bronchoconstriction

air diverted to better ventilated areas

63
Q

response when perfusion is good but ventilation is poor

A

hypoxic pulmonary vasoconstriction

blood diverted to better perfused areas

64
Q

impact of inadequeate ventilation on gas exchange

A
  • inadequate ventilation
  • V/Q reduces,
  • gas exchange within the affected alveoli is impaired
  • the capillary partial pressure of oxygen (pO2) falls and the partial pressure of carbon dioxide (pCO2) rises
65
Q

what is hypoxic vasoconstriction

A

homeostatic mechanism

causes diversion of blood to better ventilated parts of the lung.

However, in most physiological states the haemoglobin in these well ventilated alveolar capillaries will already be saturated

this means that red cells will be unable to bind additional oxygen to increase the pO2.

so the pO2 level of the blood remains low, which acts as a stimulus to cause hyperventilation

resulting in either normal or low CO2 levels.

66
Q

what can cause V/Q mismatch

A

due to either reduced ventilation of part of the lung

or

reduced perfusion.

67
Q

what is grahams law

A

the rate of diffusion is inversely proportional to the square root of its molar mass at identical pressure and temperature

68
Q

what is henrys law

A

the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid”.

69
Q

how do gasses diffuse through gases

A

the smaller the mass of a gas, the more rapidly it will diffuse.

70
Q

how do gasses diffuse through liquids

A

the more soluble a gas is, the faster it will diffuse.

71
Q

how do gasses diffuse through liquids

A

the more soluble a gas is, the faster it will diffuse.

72
Q

does carbon dioxide diffuse faster or slower than oxygen in liquids

A

faster

because it is more soluble than oxygen,

73
Q

describe membrane thickness of lungs

A

the thinner the membrane, the faster the rate of diffusion.

the diffusion barrier in the lungs is extremely thin,

74
Q

what conditions can cause thickiening of diffusion barrier in lungs (2)

A
  1. Fluid in the interstitial space (pulmonary oedema)
  2. Thickening of the alveolar membrane (pulmonary fibrosis)
75
Q

describe membrane surface area of lungs

A

the larger the surface area, the faster the rate of diffusion.

the lungs normally have a very large surface area for gas exchange due to the alveoli

76
Q

which condition reduces lung surface area

A

emphysema

leads to the destruction of the alveolar architecture
this causes the formation of large air-filled spaces known as bullae.
this reduces the surface area available and slows the rate of gas exchange

77
Q

what is surfactant

A

a phospholipoprotein that lines the alveolar walls over the water film and reduces the surface tension, keeping the alveoli open so that we can breathe properly

78
Q

define respiratory epithelium

A

pseudostratified ciliated columnar epithelium with goblet cells

79
Q

what can disruption of acid base balance lead to (2)

A

arrhythmias and seizures

80
Q

what is buffering

A

the ability of blood to be resistant to small changes in pH

this is due to the basal levels of bicarbonate and hydrogen ions in blood

81
Q

why does body maintain close control of ph

A

to ensure optimal control eg for enzyme controlled reactions in cells

82
Q

normal pH

A

7.4

83
Q

normal H+ concentration

A

40 nmol

84
Q

what happens if V/Q mismatch

A

hypoxia - oxygen deficiency at tissues

85
Q

what is hypoventilation

A

breathing that is too shallow or too slow to meet the needs of the body.

86
Q

what causes hypoventilation

A

increased CO2 level

increase H+ level

87
Q

what does hypoventilation lead to

A

build up of acid and too little oxygen in blood

  • respiratory acidosis
88
Q

what is respiratory acidosis

A

a condition that occurs when your lungs can’t remove all of the carbon dioxide produced by your body

89
Q

what is hyperventilation

A

rapid and deep breathing

90
Q

what causes hyperventilation

A

decreased CO2 level

decreased H+ level

91
Q

what does hyperventilation lead to

A

respiratory alkalosis

92
Q

what is respiratory alkalosis

A

occurs when high levels of carbon dioxide disrupt the blood’s acid-base balance

93
Q

how does the respiratory system contribute to balance of acids and bases

A

by regulating the blood levels of carbonic acid

CO2 in the blood readily reacts with water to form carbonic acid, and the levels of CO2 and carbonic acid in the blood are in equilibrium

94
Q

carbonic acid equilibrium equation

A

CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3

95
Q

how to offset acidosis

A

by ‘blowing off CO2’

or

the kidneys secrete more HCO3

96
Q

how to offset alkalosis

A

by retaining CO2

or

secreting less HCO3

97
Q

what is type 1 resp failiure

A

occurs when the respiratory system cannot adequately provide oxygen to the body, leading to hypoxemia

Low PaO2, normal PaCO

98
Q

what is type 2 resp failiure

A

occurs when the respiratory system is unable to adequately remove carbon dioxide from the body, leading to hypercapnia, and can be caused by respiratory pump failure and increased carbon dioxide production

Low PaO2, high PaCO2

99
Q

what does the henderson - hasselbalch equation do

A

relates the pH to the ratio between the concentration of bicarbonate and the partial pressure of carbon dioxide.

100
Q

what is the henderson - hasselbalch equation

A

pH = 6.1 + log10[[HCO3-] / [0.03 X PCO2]]

101
Q

what happens if you increase bicarbonate levels

A

the pH will rise and turn more alkaline

102
Q

what happens if you increase the partial pressure of carbon dioxide

A

the pH of blood will fall and turn acidic

103
Q

how does respiratory system restore blood pH

A

alters the respiratory rate, to change the concentration of carbon dioxide in the blood,

104
Q

what does the oxygen dissociation curve show

A

shows the rate at which oxygen associates, and also dissociates, with haemoglobin at different partial pressures of oxygen (pO2)

105
Q

what is partial pressure of oxygen

A

refers to the pressure exerted by oxygen within a mixture of gases; it is a measure of oxygen concentration

106
Q

what does haemoglobin saturation mean

A

when all of its oxygen binding sites are taken up with oxygen; so when it contains four oxygen molecules

107
Q

what is haemoglobins affinity for oxygen

A

The ease with which haemoglobin binds and dissociates with oxygen

108
Q

what does it mean when haemoglobin has a high affinity

A

it binds easily and dissociates slowly

109
Q

what does it mean when haemoglobin has a low affinity for oxygen

A

it binds slowly and dissociates easily

110
Q

why is oxygen dissociation a curve and not a line

A

oxygen binds with haemoglobin at different rates as the pO2 changes

It can be said that haemoglobin’s affinity for oxygen changes at different partial pressures of oxygen

111
Q

why does oxygen dissociation curve have a sigmoid shape

A

It can be said that haemoglobin’s affinity for oxygen changes at different partial pressures of oxygen

Co-operative binding means that haemoglobin has a greater ability to bind oxygen after a subunit has already bound oxygen

112
Q

what happens at high partial pressures

A

haemoglobin binds to oxygen to form oxyhaemoglobin.  All of the red blood cells are in the form of oxyhaemoglobin when the blood is fully saturated with oxygen

113
Q

what does a right shift of ODC indicate

A

decreased oxygen affinity of haemoglobin allowing more oxygen to be available to the tissues.

114
Q

what does a left shift of ODC indicate

A

increased oxygen affinity of haemoglobin allowing less oxygen to be available to the tissues.

115
Q

how does pH affect ODC

A

A decrease in the pH shifts the curve to the right - the Bohr effect

an increase in pH shifts the curve to the left. - This occurs because a higher hydrogen ion concentration causes an alteration in amino acid residues that stabilises deoxyhaemoglobin in a state (the T state) that has a lower affinity for oxygen.

116
Q

how does CO2 affect ODC

A

a decrease in CO2 shifts the curve to the left

an increase in CO2 shifts the curve to the right

CO2 affects the curve in two ways:

  1. the accumulation of CO2 causes carbamino compounds to be generated, which bind to oxygen and form carbaminohaemoglobin. Carbaminohaemoglobin stabilizes deoxyhaemoglobin in the T state.
  2. the accumulation of CO2 causes an increase in H+ ion concentrations and a decrease in the pH, which will shift the curve to the right
117
Q

how does temperature affect ODC

A

an increase in temperature shifts the curve to the right - denatures the bond between oxygen and haemoglobin, which increases the amount of oxygen and haemoglobin and decreases the concentration of oxyhaemoglobin.

a decrease in temperature shifts the curve to the left

temperature does not have a dramatic effect but the effects are noticeable in cases of hypothermia and hyperthermia

118
Q

how do organic phosphates affect OFC

A

2,3-Diphosphoglycerate (2,3-DPG) is the main primary organic phosphate.

a increase in 2,3-DPG shifts the curve to the right

a decrease in 2,3-DPG shifts the curve to the left.

2,3-DPG binds to haemoglobin and rearranges it into the T state, which decreases its affinity for oxygen.

119
Q

what are the 3 ways co2 is transported in the blood

A
  1. dissolved in plasma - 1-%
  2. bound to haemoglobin - carbaminohemoglobin - 23%
  3. as HC03- - 65%

respiratory lectures (15 decks)

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