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Physiology > L14-18: Respiratory system > Flashcards

L14-18: Respiratory system Flashcards

1
Q

What are the main functions of the respiratory system?

A

Exchange of gases
Regulation of body pH
Protection from inhaled pathogens and irritants
Vocalisation

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2
Q

Which 2 systems coordinate for gas exchange?

A

Respiratory and circulatory

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3
Q

How many lobes are each lung divided into?

A

Right three
Left two

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4
Q

What are the conducting systems compromised of?

A

Upper respiratory tract: nasal cavity, pharynx and larynx
Lower respiratory tract: trachea, bronchi, bronchioles

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5
Q

What is the respiratory zone?

A

Compromised of alveoli and capillary supply
Gas exchange surface

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6
Q

What happens in the nose and nasal cavity of the conducting system?

A

Inhaled air is warmed and humidified
Filters debris from inhaled air
Secretes antibacterial substances
Houses olfactory substances
Enhances resonance of voice

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7
Q

What happens in the pharynx of the conducting system?

A

Warm, humidify and filter inspired air
Soft palate component moves posteriorly during swelling prevents food in nasopharynx and nasal cavity
Protects against mechanical stress

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8
Q

What happens in the larynx of the conducting system?

A

Prevents foods and liquids entering respiratory tract
Sound production

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9
Q

What is in the bronchial tree?

A

2 primary bronchi
5 secondary bronchi, feeding lobes
18 tertiary bronchi, feeding lung segments
Divide into smaller bronchi
Divide into bronchioles
Terminal division into Custer of alveoli

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10
Q

What are the cross sectional areas of trachea and alveoli?

A

Trachea: 2.5cm^2
Alveoli: 1x10^6 cm^2

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11
Q

What are the epithelial cells of the conducting system?

A

Ciliated respiratory epithelial layer

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12
Q

What is the function of goblet cells?

A

Secrete mucus to form continuous mucus layer over surface of respiratory tract

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13
Q

What is the function of ciliated cells?

A

Produce saline, sweep mucus upwards to pharynx

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14
Q

What is the function of the mucociliary escalator?

A

Removes noxious particles from lungs

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15
Q

What happens in the case of cystic fibrosis?

A

Defect in CFTR channel, results in decreased fluid components of mucus = which, sticky mucus layer cannot be cleared; bacteria can colonise causing recurrent lung infections

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16
Q

What is the saline secretion pathway in airway epithelial cells?

A

CKCC brings Cl- into epithelial cell from ECF
Apical anion channels, including CFTR, allow Cl- to enter lumen
Na+ goes from ECF to lumen by paracellular pathway, drawn by electrochemical gradient
NaCl movement from ECF to lumen creates concentration gradient so water follows into lumen

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17
Q

What is the histology of the lower conducting system (larynx, trachea and primary bronchi)?

A

Lined by ciliated respiratory epithelial layer supported by c-shaped cartilage rings (keep trachea open) flexible to allow trachea diameter change during ventilation
Posterior surface covered with elastic connective tissue and smooth muscle allowing oesophagus to expand during swallowing

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18
Q

What is the histology of the lower conducting system (bronchi to bronchioles)?

A

As they divide 3 main changes occur:
Cartilage changes to complete rings, to fewer, irregular plates
Epithelium gradually changes to columnar cells in smaller bronchi
Amount of smooth muscle increases

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19
Q

What is the structure of the bronchiole?

A

Non-ciliated epithelium, smooth muscle layer, no cartilage

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20
Q

What is the structure of the vasculature?

A

Extensive capillary network, large surface area for gas exchange
Pulmonary artery supplies deoxygenated blood
Pulmonary vein carries oxygenated blood

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21
Q

What is the structure of the alveoli?

A

Single epithelial cell layer
Supported by elastic fibres
Large surface area for gas exchange

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22
Q

What is the difference between type I and II alveolar cells?

A

Type I: most common, very thin for gas exchange
Type II: smaller thicker, produce surfactant

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23
Q

What is the function of macrophages in alveolar structure?

A

Protect alveolar structures from non-filtered, small particles

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24
Q

What happens in inspiratory ventilation?

A

External intercostal muscles contract, scalenes raises rib cage upwards and outwards

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25
Q

What happens to muscles during forced breathing?

A

Internal intercostal muscles are active and accessory muscles also plays a role

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26
Q

What happens to the thoracic volume during breathing?

A

Inspiration - increases
Expiration - decreases

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27
Q

What is Boyle’s law?

A

It describes the relationship between pressure and volume
State that at constant temperature and number of gas molecules, pressure and volume of gas are inversely related

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28
Q

What happens in the process of pulmonary ventilation?

A

It involves volume changes in thoracic cavity and lungs that lead to creation of pressure gradient
Gradient causes air to move in or out of lungs

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29
Q

Which pressure gradients influence ventilation?

A

Atmospheric pressure
Intrapulmonary pressure
Intrapleural pressure

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30
Q

What is intrapulmonary pressure?

A

Air pressure within alveoli
Rises and falls with inspiration and expiration
Can equalise with atmospheric pressure due to pressure gradients reaching equilibrium

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31
Q

What is intrapleural pressure?

A

Pressure found within pleural cavity
Rise and falls with inspiration and expiration
Does not equalise with atmospheric pressure

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32
Q

What is the pleural sac?

A

What lungs are found within
Formed by two membranes of elastic connective tissue and capillaries

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33
Q

What is the parietal pleura?

A

The outer layer of serous membrane, fused to rib cage, diaphragm and other local structures

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34
Q

What happens to parietal pleura at hilum?

A

It turns over on itself to create visceral pleura, the inner layer of membrane continuous with the surface of lungs

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35
Q

What is pleural fluid?

A

Very thin film of fluid within cavity
Acts as lubricant to allow lung to move within thorax
Maintains lung inflation at rest

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36
Q

Why does intrapleural pressure vary along the lung?

A

Due to gravity and during the respiratory cycle

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37
Q

Where is there elastic recoil?

A

Of the lungs
Of the chestwall

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38
Q

What pressure changes are there in pulmonary ventilation?

A

Inspiration: intrapulmonary decrease, intrapleural decreases
Expiration: intrapulmonary increases, intrapleural increases

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39
Q

What happens during inspiration of pulmonary ventilation?

A

Decrease in intrapleural pressure causing alveoli to expand and atmospheric pressure is greater than alveolar pressure so air enters the lungs

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40
Q

What is alveolar gas exchange influenced by?

A

O2 reaching alveoli: composition of inspired air
Alveolar ventilation: rate and depth of breathing, airway resistance, lung compliance
Gas diffusion between alveoli and blood: surface are and diffusion distance (barrier thickness and amount of fluid)
Adequate perfusion of alveoli

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41
Q

What are the 3 primary physical factors effecting pulmonary ventilation?

A

Airway resistance - anything that impedes air flow through respiratory tract
Alveolar surface tension - thin film of liquid (mainly water) covering alveoli so gas-water boundary
Lung compliance - ability of lungs and chest wall to stretch

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42
Q

What is airway resistance determined by?

A

Length of system
Airway diameter (wider = less resistance)
Flow (laminar - low or turbulent - high)
Viscosity of gas

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43
Q

What is the ratio between that determines airway resistance?

A

Driving pressure (ΔP) : rate of air flow

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44
Q

Which vessel has the highest resistance?

A

Bronchi

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45
Q

When is resistance of airways increased?

A

In inflammation, increased mucus secretion, e.g. presence of tumour

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46
Q

What is diameter of bronchi controlled by?

A

Smooth muscle contraction and relaxation

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47
Q

Which central system controls bronchial tone?

A

Parasympathetic (bronchoconstriction)

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48
Q

What is a non-neural control of bronchial tone?

A

Sympathetic β2 receptors present on smooth muscles activated by circulating adrenergic agonists

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49
Q

How is a gas-water boundary formed on alveolar surface?

A

Water molecules form hydrogen bonds
Gases are non polar molecules and therefore do not form hydrogen bonds

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50
Q

How is surface tension created in alveoli?

A

When alveoli are at their smallest diameter during expiration
Increased surface tension resists ability of alveolus to inflate

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51
Q

How does surfactant impact alveoli?

A

It reduces the surface tension allowing smaller alveoli to inflate easier

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52
Q

What is atelectasis?

A

When a high amount of unopposed surface tension causes alveolus to collapse during expiration

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53
Q

What is surfactant?

A

Mixture of proteins and phospholipids
Similar to detergent (polar and non polar)

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54
Q

Where is surfactant secreted?

A

It is produced by type II alveolar cells

55
Q

Why can newborns suffer from respiratory distress syndrome (RDS)?

A

Because surfactant is not produced significantly until the last 10-12 weeks of gestation

56
Q

What is compliance defined as?

A

A change in volume produced by a change in pressure

57
Q

What is compliance affected by?

A

Alveolar surface tension
Distensibility of elastic tissue
Ability of the chest wall to stretch/move during inpiration

58
Q

When is there an increase in lung compliance?

A

When there is an increase in change of volume and a constant change in pressure

59
Q

Which diseases impact compliance and how do they?

A

Emphysema (loss of alveoli - less elastic recoil) shifts left to normal compliance
Fibrosis (elastic tissue replaced with scar tissue) shift right to normal compliance

60
Q

What can be used to measure lung volume and capacity?

A

A spirometer

61
Q

What is tidal volume?

A

Volume inspired or expired with each normal breath = 500ml

62
Q

What is expiratory reserve volume?

A

Maximal volume that can be expired after the expiration of a tidal volume/ normal breath = 1200ml

63
Q

What is inspiratory reserve volume?

A

Maximum volume that can be inspired over the inspiration of a tidal volume/ normal breath = 3100ml

64
Q

What is residual volume?

A

Volume that remains in the lungs after a maximal expiration = 1200ml

65
Q

Which pulmonary volumes can be measured using spirometry?

A

TV, ERV, IRV

66
Q

What is inspiratory capacity?

A

Volume of maximal inspiration TV+IRV = 3600ml

67
Q

What is functional residual capacity?

A

Volume of gas remaining in lung after normal expiration ERV+EV = 2400ml

68
Q

What is vital capacity?

A

Volume of maximal inspiration and expiration IRV+TV+ERV=IC+ERV= 4800ml

69
Q

What is total lung capacity?

A

The volumes of the lung after maximal inspiration = sum of all lung volumes

70
Q

What if FEV1?

A

Forced expiratory volume in 1 second, volume expired in the 1st second of forced expiration

71
Q

What do restrictive and obstructive FVCs indicate?

A

Restrictive lung disease - FVC reduced, FEV1 close to normal (pulmonary fibrosis)
Obstructive lung disease - FVC close to normal, FEV1 reduced (asthma, bronchitis)

72
Q

What is dead space?

A

Anatomically: volume of conducting airways
Physiological: anatomic dead space + alveolar dead space
Alveolar: In unhealthy/elderly not all alveoli function properly

73
Q

What is the equation for total pulmonary ventilation?

A

Total pulmonary ventilation = ventilation rate x tidal volume

74
Q

What is the equation for alveolar ventilation?

A

Alveolar ventilation = ventilation rate x (tidal volume - dead space volume)

75
Q

What are the factors affecting the diffusion of gas?

A

Pressure gradient
Solubility of gas in a liquid
Temperature

76
Q

What is Dalton’s law?

A

The total pressure exerted by a mixture of gases is equal to the sum of the pressures exerted by the individual gases

77
Q

How is partial pressure of a gas determined?

A

Partial pressure of a gas = atmospheric pressure x percentage of gas

78
Q

How does partial pressure change at sea level and in the alveoli?

A

Nitrogen - little change
Oxygen - decreased
CO2 - increased
H2O - 47mmHg

79
Q

What is Henry’s law regarding solubility of gas?

A

At constant temperature, the amount of gas that dissolves in a liquid depends on the solubility of the gas in the liquid and the partial pressure of the gas

80
Q

What is movement of gas directly proportional to?

A

Pressure gradient of the gas
PO2 alveoli > PO2 blood
PCO2 alveoli < PCO2 blood
Solubility of gas in liquid
CO2 solubility > O2 solubility
Temperature
Alveoli air at core body temperature

81
Q

What are the characteristics of pulmonary circulation?

A

Low pressure system
high flow

82
Q

What is the flow of pulmonary circulation?

A

Right ventricle to pulmonary trunk to pulmonary arteries to lungs to pulmonary veins to left atrium

83
Q

What is flux?

A

The ability to move across the membrane

84
Q

What is Fick’s law of diffusion?

A

Flux = (P x ΔC) / X
P = permeability of barrier x surface area
ΔC = Concentration gradient across membrane barrier
X = distance to diffuse

85
Q

What is gas exchange driven by?

A

Concentration gradient

86
Q

What happens in hyper and hypoventilation?

A

Hyper: increased alveolar pressure of O2 and decreased CO2
Hypo: decreased alveolar pressure of O2 and increased CO2 and hypoxemia

87
Q

What does hyperbaric mean?

A

Higher than normal pressure

88
Q

When is hyperbaric oxygen therapy used?

A

To treat conditions benefiting from increased O2 delivery: severe blood loss, crush injuries, anaemia, chronic wounds, certain infections, burns and recovery
Used for decompression sickness:
Divers who ascend too rapidly
Dissolved gases in blood coming out of solution and forming bubbles in bloodstream, forces gases back into solution

89
Q

Which diseases have problems with diffusion in gas exchange?

A

Emphysema, fibrotic lung disease, pulmonary edema and asthma

90
Q

What does alveolar ventilation depend on?

A

Posture
Rate of inspiration
Amount of air inspired

91
Q

What does lung perfusion depend on?

A

Hydrostatic pressure in pulmonary arteries
Pressure in pulmonary veins
Alveolar air pressure

92
Q

What happens to alveolar ventilation and lung perfusion when upright and normal inspiration occurs?

A

Alveolar ventilation: base of lung more ventilated than apex
Lung perfusion: Base of lung more perfused than apex

93
Q

What is hypoxic pulmonary vasoconstriction?

A

Redirects blood flow to ventilated alveoli
Improved gas exchange
Contrast with systemic circulation

94
Q

What are arteriole and bronchiole diameters controlled by?

A

Oxygen and carbon dioxide

95
Q

How is oxygen transported in the blood?

A

<2% dissolved in plasma
>98% bound to haemoglobin in RBC

96
Q

What is percentage saturation of Hb affected by?

A

PCO2, pH, temperature and 2,3-bisphosphoglycerate

97
Q

How does the O2-Hb saturation curve change during exercise?

A

PO2 arterial blood - stays the same
PO2 at issue level - stays the same/ decreases
An increase of O2 dissociated from HbO4

98
Q

What effect does CO2, pH and temperature have on oxygen saturation?

A

Lower PCO2 = shift to left
Higher PO2 = shift to right
Lower pH = shift to right
Higher pH = shift to left
Lower temperature = shift to right
Higher temperature = shift to left

99
Q

What does the Bohr effect describe?

A

The reduction in oxygen affinity of haemoglobin when pH is low and the increase in affinity when pH is high

100
Q

When is haemoglobin in the tense (T) conformation?

A

When H+ is bound to it
Promotes release of O2 in areas of high CO2 concentration

101
Q

How does 2,3-disphosphoglycerate impact the oxygen saturation curve?

A

No 2,3-DPG = shift to left
Added 2,3-DPG = shift to right

102
Q

How does 2,3-DPG help oxygen saturation?

A

It interacts with the β-chains of haemoglobin
Improves O2 delivery to tissue which might otherwise become hypoxic

103
Q

When 2,3-DPG increased?

A

Chronic lung disease
Anaemia
Congestive heart failure
Lower atmospheric PO2

104
Q

What happens to oxygen saturation during anaemia?

A

Curve shifts to the right
Oxygen content decreased
Oxygen easily dissociates
Occurs at higher PO2 than normal
Due to increased 2,3-DPG concentration

105
Q

What is the difference between foetal haemoglobin and maternal?

A

2α and 2γ globing
2nd month pregnancy ~6 months old
Higher affinity for O2 than maternal
Shift to left

106
Q

How is CO2 transported in the blood?

A

Venous blood:
Binds to Hb
Carbonic acid in plasma (using chloride shift)
Dissolved in blood

107
Q

How does carbonic acid form in the blood?

A

Using carbonic anhydrase enzyme with CO2 and H2O

108
Q

What are the 2 effects of carbon monoxide?

A

Limits the amount of oxygen Hb can carry
Shifts Hb to the relaxed conformation, O2 is more tightly bound and not dissociated at low PO2

109
Q

What is the treatment for carbon monoxide poisoning?

A

Hyperbaric oxygen therapy

110
Q

What role does nitric oxide play in oxygen haemoglobin?

A

Causes vasorelaxation
Binding to haemoglobin ends NO reactivity
May mediate O2 delivery - opens blood vessel to allow RBC passage
Shifts curve to left
Binding is complex

111
Q

What type of inputs impact the pattern of ventilation?

A

Peripheral and central chemoreceptors
Irritant receptors
Stretch receptors in lungs
Respiratory centres
Receptors in muscles and joints

112
Q

What are the different stimuli that can impact control of ventilation?

A

Emotions and voluntary control
CO2
O2 and pH

113
Q

What does the medulla control in respiration?

A

Generates automatic rhythmic breathing pattern
2 groups neurones: Dorsal respiratory group (DRG)
Ventral respiratory group (VRG)

114
Q

What are pons?

A

Site of pontine respiratory group (PRG)

115
Q

Which groups and centres are important in the brain?

A

Apneustic centre
Dorsal respiratory groups (nucleus tractus solitairius)
Ventral respiratory groups: Botzinger’s complex

116
Q

Which cervical spinal nerves control the diaphragm?

A

C5-7

117
Q

What are the thoracic spinal nerves?

A

T1-11

118
Q

What do the DRG regulate?

A

Automatic rhythmic breathing

119
Q

What is the respiratory cycle generated by DRG neurones?

A

DRG active, inspiratory muscles contract, inspiration occurs, dorsal respiratory group inhibited, inspiratory muscles relax, passive expiration occurs

120
Q

What are the roles of pons?

A

Apneustic centre:
located dorsally in the pons
Promotes inspiration by stimulating the inspiratory neurones in medulla
Pneumotaxic centre:
Upper part of pons
Antagonises and dominates apneuistic
Inhibits inspiration, allows for smooth breathing

121
Q

What modifies respiratory rate?

A

Decrease in PO2 - results in high respiratory rate

122
Q

Where are chemoreceptors found?

A

Two locations:
Aortic bodies - aortic arch
Carotid bodies - bifurcation of internal and external carotid artery

123
Q

How do the chemoreceptors transmit information?

A

Aortic via vagus nerve
Carotid via glossopharyngeal nerve

124
Q

What is the ventilatory response to low PO2?

A

Hyperventilation which decreases PCO2 and elevates PO2

125
Q

What is the signalling pathway in carotid body?

A

Low PO2
K+ channels close
Cell depolarises
Voltage-gated Ca2+ channel opens
Ca2+ entry
Exocytosis of dopamine-containing vesicles
Signal to medullary centres to increase ventilation

126
Q

What does ventilation primarily respond too?

A

Changes in PCO2

127
Q

What happens when a high PCO2 is sneezed by chemoreceptors?

A

Hyperventilation
Adaptation after several days at high PCO2, respiratory rate returns to normal

128
Q

What happens to pH in hyperventilation?

A

Respiratory alkalosis
More CO2 expired
Blood CO2 decreases
Carbonic acid releases fewer H+
H+ concentration decreases
Blood pH increases

129
Q

What happens in metabolic acidosis?

A

Results from increase in non-CO2 derived acid
H+ ions excluded from entering CSF by blood brain barrier - cannot stimulate chemoreceptors, sensed by peripheral receptors

130
Q

What is the principle of compensation?

A

In response to metabolic acid-base disturbance
Rapid response
Does not correct initial defect
Metabolic alkalosis inhibits respiration to retain CO2 in body and reduce pH

131
Q

What is the Hering Breurer reflex?

A

Prevents over-inflation
Stretch receptors in lung smooth muscle
Activation - cessation of inspiration, onset of expiration
Role - respiration rate and depth in newborn

132
Q

What are the irritant receptors?

A

Stimulated by mechanical stimuli
Rapid adaptation when stimulated continuously
Impulses via myelinated fibres in vagus
Rapid shallow breaths and the cough reflex

133
Q

How is a cough produced?

A

Irritant receptors triggered
Impulse via vagus and superior laryngeal nerves to medulla: DRG & VRG activated
Diaphragm and external intercostal muscles contract
Pressure in pleural cavity decreases: air enters lungs
Glottis and larynx close
Abdominal and other muscles contract pressure in lungs increase
Glottis and larynx open air released at high speed
Bronchi and non-cartilaginous trachea collapse air forced through

134
Q
A

Physiology (6 decks)

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