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MEDSCI 142 > Section 5: Respiratory System > Flashcards

Section 5: Respiratory System Flashcards

1
Q

What 2 things are essential for efficient exchange

A

Diffusion distance between air and blood must be small
Surface area over which exchange takes place must be large

Both are achieved in human lungs
Diffusion distance ~0.5µm
Internal SA of lungs ~100m^2

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2
Q

Respiration

A

The transfer of gas (O2 / CO2) across a boundary

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3
Q

External respiration

A

The process in the lungs by which oxygen is absorbed from the atmosphere into blood within the pulmonary capillaries, and CO2 is excreted
i.e. air –> blood

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4
Q

Internal / tissue respiration

A

The exchange of gases between blood in systemic capillaries and the tissue fluid and cells which surround them
i.e. blood - tissues

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5
Q

Cellular respiration

A

The process within individual cells through which they gain energy by breaking down molecules (e.g. glucose)

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6
Q

Pulmonary ventilation

A

AKA breathing

The bulk movement of air into and out of the lungs

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7
Q

What is the ventilatory pump comprised of

A

Rib cage with its associated muscles and the diaphragm

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8
Q

Functional classification of respiratory system

A

Conducting part/zone

Respiratory part/zone

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9
Q

Structural classification of respiratory system

A

Upper respiratory tract

Lower respiratory tract

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10
Q

Conducting zone of respiratory system

A

A series of cavities and thick-walled tubes which conduct air between the nose and deepest recesses of lungs
Warms, humidifies, and cleans air
No gas exchange

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11
Q

Conducting airways

A 
Nasal cavities
Pharynx
Larynx
Trachea
Bronchi
Some bronchioles
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12
Q

Respiratory zone of respiratory system

A

Comprises the tiny, thin-walled airways where gases are exchanged between air and blood
Undergoes gas exchange

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13
Q

Respiratory zone - airways

A

Respiratory bronchioles
Alveolar ducts and sacs
Alveoli

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14
Q

Upper respiratory tract

A

Nose –> larynx

Less extreme infections

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15
Q

Lower respiratory tract

A

Trachea –> alveoli

Closer to blood supply –> more extreme infections

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16
Q

Pathway of gases during respiration

A

O2: Ventilatory pump (air) —external respiration—> left cardiac pump —internal respiration—> cells / cellular respiration

CO2: Cells —internal respiration—> right cardiac pump —external respiration—> ventilatory pump

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17
Q

Purpose of upper respiratory tract

A

Prepare air for gas exchange:

  • Warm –> 37°C
  • Clean –> filter
  • Wet –> humidify –> 100% saturate with H2O
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18
Q

Nasal cavity - turbinates

A

Increases surface area of nasal cavity

Turbulence - mixes the air and slows it down

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19
Q

Nasal cavity - vibrissae

A

Coarse hair filter

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20
Q

Nasal cavity - respiratory epithelium

A

Pseudostratified columnar ciliated epithelium (filters and humidifies) + goblet cells (source of mucous)

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21
Q

Nasal cavity - seromucous gland

A

Underneath epithelium
Mucous filter
Water humidification

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22
Q

Nasal cavity

A

A tall, narrow chamber lined with mucous membrane

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23
Q

Nasal cavity - purpose of wet membrane

A

Humidifies and warms inspired air

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24
Q

Nasal cavity - surfaces

A

Medial surface is flat

Lateral surface carries conchae (3 sloping shelves) that increase SA of mucous membrane

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25
Q

Nasal cavity - paranasal sinuses

A

Air-filled sinuses that open into the cavity

Lighten the face and add resonance to voice

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26
Q

Nasal cavity - olfactory epithelium

A

Found on roof of cavity
Turbulence caused by sniffing carries air up to epithelium
Axons of olfactory receptor cells lead towards the brain through cribriform plate (perforations in the overlying bone)

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27
Q

Parts of the pharynx

A

Nasopharynx
Oropharynx - part of digestive system
Laryngopharynx

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28
Q

Pharynx

A

A vertical passage with three parts, each having an anterior opening
An airway and a foodway - primarily part of the GI system

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29
Q

Epiglottis

A

An elastic cartilage

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30
Q

Branching: Conducting zone - structures and (generations)

A 
Trachea (0)
1° / Main stem bronchi (1)
2° / Lobar bronchi (2)
3° / Segmental bronchi (3)
Smaller bronchi (4-9)
Bronchioles (10-15)
Terminal bronchioles (16-19)
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31
Q

Branching: Respiratory zone - structures and (generations)

A 
Respiratory bronchioles (20-23)
Alveolar ducts (24-27)
Alveolar sacs (28)
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32
Q

Branching of airways

A

One tube will only branch into 2, and it narrows

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33
Q

Branching: 20th generation

A

~20th generation is where the air should be clean

Infection beyond the 20th generation might become more serious

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34
Q

Windpipe

A

A tube ~12cm long and as thick as your thumb
Supported by incomplete C-shaped rings of cartilage
Lined with pseudostratified ciliated columnar epithelium

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35
Q

Windpipe - Trachealis muscle

A

Smooth
Connects the free ends of the cartilage
Contraction narrows the diameter of the trachea

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36
Q

Windpipe - cilia

A

Transport a mucous sheet upwards to the nasopharynx (mucociliary escalator)

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37
Q

Mucociliary escalator

A

100-300 cilia per cell
Don’t all move at the same time
‘Mexican wave’

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38
Q

Oesophagus

A

Sits immediately posterior to trachea

Lies in shallow groove formed by the trachealis muscle

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39
Q

Smoking - mucous

A

Smoking overstimulates mucous production –> smoker’s cough with lots of mucous by generating huge pressures to move the mucous

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40
Q

Sinuses

A

Big spaces within our face which are connected

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41
Q

Pathway of respiratory system

A

Nose –> nasal cavity –> pharynx –> larynx –> trachea –> bronchi –> lungs

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42
Q

Sources of mucous in trachea and bronchus

A

Goblet cells

Glands

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43
Q

Bronchi - branching and size of cells

A

As they branch, the epithelia height gets smaller
Goes from pseudostratified columnar to cuboidal to flat squamous cells because need thin layer for gas to diffuse efficiently

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44
Q

Bronchioles

A

Tubes can keep themselves open

Most air is conditioned - don’t need that much mucous anymore, just need to keep the lining wet

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45
Q

Wall of a bronchiole: Club cells

A

AKA Clara cells
Not ciliated
Watery secretion –> H2O
Anti-microbial enzymes

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46
Q

Wall of a bronchus: Goblet cells - cilia

A

Not ciliated

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47
Q

Wall of a bronchiole: Smooth muscle

A

Controls diameter of tube

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48
Q

Wall of a bronchiole: Thickness

A

Much thinner than bronchus because we lose structures we don’t need anymore

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49
Q

Bronchodilation and bronchoconstriction

A

Controls tone of airways

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50
Q

Acute asthma attack

A

Rapid bronchoconstriction

Treat with bronchodilater (salbutamol / ventolin) - relaxes smooth muscle

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51
Q

Cell types present in alveolus

A
  1. Squamous pneumocyte (type I alveolar cells)
  2. Surfactant cells (type II alveolar cells)
  3. Alveolar macrophage
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52
Q

Alveolus: Surfactant cells

A

Prevent collapse of alveoli on expiration –> decreases work of breathing
Repel each other constantly

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53
Q

Work of breathing

A

Amount of energy required to inspire

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54
Q

Alveolus: Premature babies

A

< 30 weeks
Have low no of surfactants, so every time they exhale, their alveoli collapse
Can lead to neonatal respiratory distress

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55
Q

The diffusion barrier

A

AKA blood-air barrier

External respiration

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56
Q

Diffusion barrier: Fibrosis

A

An increased amount of CT leads to increased distance

Individual becomes hypoxic

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57
Q

Airway: Cartilage

A

Supports the large airways during inspiration
Doesn’t continue beyond the smallest bronchi
Mucous glands also stop here

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58
Q

Airway: Thickness of epithelium and diameter

A

Thickness of epithelium decreases as airway diameter decreases

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59
Q

Airway: Goblet cells vs Club cells

A

Goblet cells secrete mucous in the large airways

Club cells release a serous (watery) secretion in bronchioles

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60
Q

Small airways: Smooth muscle

A

Have more smooth muscle (in spiral orientation) in relation to their size than large ones
But muscle coat doesn’t continue beyond the smallest bronchioles

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61
Q

Subdivisions of the lung

A

Primary bronchi: right and left main stem bronchi supplying each lung
Secondary bronchi: lobar bronchi supplying lobes (2 on left, 3 on right)
Tertiary bronchi: segmental bronchi supplying segments of lung (8 on left, 10 on right)

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62
Q

Segment of lung

A

Each segment has its own air and blood supply

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63
Q

Tumours in lungs

A

When a localised tumour occurs in the lung, can remove one or more segments containing the tumour without excessive leakage of air or blood from neighbouring segments

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64
Q

Each segment is encased in…

A

CT

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65
Q

Each segment of the lung is being supplied by…

A

A segmental (tertiary) bronchus

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66
Q

Pleurae

A

A smooth membrane that covers each lung
Also lines thoracic cavity in which the lung sits
The 2 membranes are continuous at the hilum

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67
Q

Hilum

A

The root of the lung

Where the main stem bronchus enters the lung

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68
Q

What separates the pleurae

A

A thin film of fluid
Allows pleurae to slide past each other without friction
Prevents them from being separated - when thoracic wall moves inward, outward, upward, or downward, lungs must follow

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69
Q

Quiet breathing - ribcage

A

Movement of ribcage is responsible for ~25% of air movement into and out of lungs

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70
Q

Quiet breathing - inspiration and expiration

A

Inspiration is active - requires contraction of external intercostal muscles
Expiration is passive - ribcage returns to its resting position without requiring muscular action

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71
Q

External intercostal muscles

A

Run obliquely between ribs

During exercise, the contraction of them has the effect of lifting the ribs

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72
Q

Breathing during exercise - intercostal muscles

A

Both sets of intercostal muscles are now active
Externals for inspiration
Internals for expiration

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73
Q

Ribs - structure

A

Pivot around their joints with the vertebral column

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74
Q

Internal intercostal muscles - structure

A

Run at right angles to the externals

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75
Q

Internal intercostal muscles - function

A

When they contract, they drag the ribs downwards

Active contraction only occurs during forceful exhalation

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76
Q

Diaphragm - structure

A

A dome-shaped platform that forms the floor of the thorax and roof of the abdomen
Lateral margins are muscular - fast-acting skeletal muscle, innervated by the phrenic nerve

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77
Q

Central tendon

A

Central part of the diaphragm

A thin sheet of CT (aponeurosis)

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78
Q

Diaphragmatic muscle - contraction

A

Flattens the diaphragm, pulling its central dome downwards

Increases V of thorax –> inspiration

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79
Q

Diaphragmatic muscle - passive relaxation

A

Allows diaphragm to lift back towards thorax

Reduces thoracic V –> expiration

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80
Q

Diaphragm - quiet breathing

A

Movement of diaphragm is responsible for 75% of bulk flow of air during quiet breathing (smaller proportion during exercise)

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81
Q

Definition of respiration

A

To extract oxygen from the air and tgt with the cardiovascular system transport it to respiring tissues
Remove CO2 from respiring tissues and exhaust into atmosphere

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82
Q

Respiratory and cardiovascular system

A

Works tgt / coupled tgt

If exercising and CO2 doesn’t increase blood flow through lungs, there’s no point as nothing to supply the O2

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83
Q

Evolution of respiration

A

Increase in:
Size
Distance
Metabolic rate

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84
Q

Respiratory motor nerves

A

Phrenic motor neurons (C3-C5)
Intercostal motor neurons (T1-L1)
Abdominal motor neurons (T7-L1)

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85
Q

Evolution of respiration - mammals

A

Mammals are warm-blooded, so need more O2 - require efficiency

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86
Q

Contraction of muscles involved in inspiration / expiration

A

Must contract them in an ordered sequence - have a sophisticated neural mechanism to do this

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87
Q

Central pattern generator / neural oscillator

A

Drives neural impulses that descend down the spinal cord to innervate the diff groups of motor neurons

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88
Q

Respiratory motor nerves: Phrenic motor nerves

A

Branches feed the phrenic nerve (which innervates the diaphragm)

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89
Q

What is the main respiratory muscle

A

Diaphragm

~70% of inspiration

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90
Q

Respiratory motor nerves: Intercostal motor neurons

A

Innervate internal and external intercostal muscles

Exist between ribs

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91
Q

Internal vs external intercostal muscles - contraction

A

Internal - contract during expiration
External - contract during inspiration

Never contract simultaneously

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92
Q

Respiratory motor nerves: Abdominal motor neurons

A

Innervate the abdominal nerve; rectus abdominus
Resting = little activity
Exercise = abdominal muscles start to contract during expiration - forces expiration –> increase respiratory rate

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93
Q

Rectus abdominus

A

Expiratory muscle

Only active during active expiration, e.g. cough, retch, laugh

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94
Q

Respiratory motor neurons: Respiratory rhythm

A

LMNs don’t generate respiratory rhythm - in isolation from the brain, can’t produce the breathing needed
Generated in UMNs in brainstem

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95
Q

High cervical lesion in spinal cord

A

Breathing stops because generator for synchronisation for inspiration and expiration is generated in the brainstem

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96
Q

Diaphragm - structure

A

Shaped like a parachute

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97
Q

70% of inspiratory effort is produced by…

A

Diaphragm contraction

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98
Q

Diaphragm and ribs - contraction

A

Diaphragm contracts downwards (flattens) and moves outwards. Doms back up when expiring
Ribs move upwards and outwards

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99
Q

Thoracic cavity - inspire

A

Thoracic cavity of chest gets bigger in 3 dimensions when you inhale

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100
Q

What does expiration rely on

A

Elasticity of thorax and lungs to bring diaphragm back to resting state
At rest, this is passive - no energy required

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101
Q

Inspiration is always ___

A

Active

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102
Q

Respiratory cycle

A

The inspiratory and expiratory parts we undergo when we’re breathing
From one period of inspiration to the next period of inspiration

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103
Q

Parts of a respiratory cycle

A

2 parts:
Inspiration (active)
Expiration (passive)

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104
Q

How much air will an average person at rest breathe in

A

Half a litre of air

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105
Q

Over the course of the day, an average person breathes in how much air

A

~8,500 litres

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106
Q

Breathing - voluntary?

A

Kind of voluntary - can control, but is also automatic

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107
Q

Tidal volume AKA

A

Tidal breath

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108
Q

Pleura membranes

A

Parietal pleura - runs along outside of chest wall

Visceral pleura - runs around lungs

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109
Q

What is found between the pleura membranes

A

A pleural cavity filled with fluid

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110
Q

Ppul

A

Pulmonary pressure

Pressure within airways of lungs

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111
Q

Ppl

A

Pleural pressure

Pressure from pleural cavity

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112
Q

Why does air move into lungs

A

Before its moving from an area of higher (atmosphere) to lower (lungs) pressure

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113
Q

Inspiration - pressure

A

During inspiration, you create an area of lower pressure relative to atmosphere within airways of lungs so air is drawn in

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114
Q

Respiratory cycle - atmospheric pressure

A

Taken as zero

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115
Q

Respiratory cycle - steps

A

Before you take your next breath, it’s always -3cm of water relative to atmospheric P - means you have -ve pressure around your lungs
-ve pressure –> lung adheres to inside of chest - if chest wall moves, lung follows –> lung inflates in 3D

When you inspire, Ppl becomes more -ve –> pulmonary P also becomes -ve relative to atmosphere

When you expire, Ppl becomes less -ve –> P within airways become +ve relative to atmospheric –> air moves from lungs to atmosphere

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116
Q

Respiratory cycle: What causes air to move from an area of higher to lower pressure into lungs

A

The -ve pulmonary pressure within airways relative to the atmosphere

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117
Q

Respiratory cycle: Why is Ppl important

A

Initial -ve value of Ppl essential to prevent lungs from collapsing
So, Ppl either becomes more -ve or less -ve, never becomes +ve

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118
Q

Pneumothorax

A

Wounded rib cage by a thoracic puncture wound –> lung moves away from wall and deflates
Air rushes into chest
Loss of -ve pleural pressure

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119
Q

Pneumothorax - treatment

A

Reinflate the lung by repairing the puncture wound and reinstating the -ve pressure around the lungs

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120
Q

Spirometer - structure

A

External floating drum (upside down) sits in an inner cylinder of water
Inner cylinder is supported by pulleys, a small wire, and a counterbalancing weight. Also has a tube that allows you to access the air in the floating drum

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121
Q

Spirometer - mouthpiece

A

Attached to tube of inner cylinder

When you breathe through the mouthpiece, can push the floating drum up and down - can measure respiratory V and capacity

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122
Q

Respiratory volume vs respiratory capacity

A

Respiratory V is measured

Respiratory capacity is calculated (often combining 2 or more Vs)

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123
Q

Inspiratory reserve volume (IRV)

A

The amount of extra inspiration you can do above a normal tidal breath

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124
Q

Expiratory reserve volume (ERV)

A

The max amount of air you can blow out of your lungs after a normal expiration
May need these reserve Vs during exercise

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125
Q

Functional residual capacity (FRC)

A

Resting point of lung

After expiration just before you take your next breath in

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126
Q

Residual volume (RV)

A

The V of air in your lungs that you can’t blow out because small airways in lungs will collapse due to expiratory exhalation force around lungs - left with a pocket of air in alveoli

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127
Q

Total lung capacity = ?

A

VC (can measure) + RV (can’t measure)

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128
Q

Average number of breaths per min for an adult

A

~12 breaths per min and 500mL per breath

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129
Q

Respiratory volume: What is V(T)

A

Tidal breath

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130
Q

Respiratory volume: f

A

Respiratory frequency

131
Q

Respiratory volume: V(E) with dot on top of V

A

Minute ventilation
= V(T) x f
= 0.5 x 12 = 6 L/min

Also = V(A) + V(D)

132
Q

Respiratory volume: What does the dot above the V on V(E) indicate

A

Indicates it is a time derivative

133
Q

Hyperventilation vs hypoventilation

A

Hyper is > 6L/min

Hypo is < 6 L/min

134
Q

Respiratory volume: V(A) with dot on top of V

A

Alveolar ventilation
= V(E) - V(D)
= (0.5 - 0.15) x 12 = 4.2 L/min

135
Q

Respiratory volume: V(D) with dot on top

A

Dead space ventilation
Anatomical dead space
Approx 150mL - doesn’t go to alveoli, so doesn’t contribute to ventilation
~2.2 mL/kg

136
Q

Alveolar ventilation allows you to understand…

A

Gas exchange

137
Q

Anatomical dead space is found where

A

In conducting space/zone - full of air not being used for gas exchange

138
Q

Calculating total lung capacity - process

A

Connect spirometer to subject and fill it with enough gas that doesn’t go into bloodstream (stays within lungs, e.g. He)
Open valve and let equilibration occur - will be more dilute because now have V of both spirometer and lungs

139
Q

Calculating total lung capacity - V2

A

We know conc and V of spirometer, so can calculate V2 (total lung capacity)

140
Q

Calculating total lung capacity - calculation steps

A

V2 = V1(C1-C2) / C2
V1: initial volume in spirometer
C1: initial conc of helium in spirometer
C2: helium conc after equilibration

Residual V = TLC (or V2) - vital capacity

141
Q

Testing lung health - types of values

A

FEV1: Forced expiratory volume in 1 sec
FVC: Forced vital capacity, usually less than during a slower exhalation. Total amount of air you can blow out

142
Q

Testing lung health - normal values

A 
FEV1 = 4.0L
FVC = 5.0L

FEV1/FVC = 80%

143
Q

Testing lung health - ratios

A

Tells physician what type of respiratory problem someone has

144
Q

Testing lung health - asthma

A

Both FEV1 will be smaller than normal

FVC may be normal

145
Q

Recoil force consists of…

A

Elasticity of the lungs

Surface tension in the lungs

146
Q

What is recoil force

A

The combined forces that allow the lungs to deflate and push air out of airways into the atmosphere

147
Q

Elasticity

A

Ability to recover original size and shape after deformation

Allows for lungs to change their volume dramatically

148
Q

Parenchyma

A

A matrix in the lungs full of tubes, e.g. airways, vessels, alveoli
Holds the lung together by natural elastic fibres and collagen

149
Q

Lungs - elastin

A

Allows lung to inflate and deflate

150
Q

Lungs - collagen

A

Provides structure

151
Q

Elastin and collagen - inspiration and expiration

A

As you go from expiration to inspiration, the intrinsic fibres of elastin and collagen get stretched and pull the tubes open

152
Q

Radial traction

A

An important mechanism through which the lungs can deflate - a force that keeps the lungs open
To do with parenchyma - as inspiration takes place, traction increases

153
Q

Compliance = ?

A

1/elasticity
or
change in V / change in P

154
Q

What is compliance

A

How easy it is to blow the lungs up and how far they stretch

155
Q

What is a compliant lung

A

Easy to inflate and needs little pressure

156
Q

What is surface tension

A

The enhancement of intermolecular attractive forces at the surface
Due to the surface (at a liquid-gas interface) having no neighbouring atoms above –> exhibit stronger attractive forces upon their nearest neighbours on the surface

157
Q

Where is the liquid-gas interface found in the lung

A

In each alveolus

Gas comes into the alveoli, and membrane of alveoli has a thin film of liquid

158
Q

We have ______ alveoli

A

~300 million

159
Q

Laplace’s law - equation

A

P = 2T / R

160
Q

Laplace’s law - alveoli

A

Alveolus has greater pressure than atmosphere, i.e. a +ve pressure that’s trying to collapse the alveolus, known as collapsing pressure

161
Q

What does surface tension contribute

A

Contributes a force for deflating the lungs

162
Q

Alveoli radius and pressure

A

Alveoli of diff radii will affect the collapsing pressure that is generated

163
Q

Why does the lung have cells that secrete surfactant

A

Collapsing pressure generated would oppose the force required to inflate the lung quite dramatically, so lung secretes surfactant

164
Q

Surfactant

A

Like a soap - reduces intermolecular forces and surface tension so lungs become more complacent
Must be moderated because it’s quite a strong force

165
Q

Compliance relationship of the lung

A

Compliance (P-V curve) has a fairly linear relationship

But there are some diseases that can affect this relationship –> detrimental effect on how they breathe

166
Q

Chronic obstructive pulmonary disease (COPD) - compliance

A

Lungs become more compliant because need less pressure change to produce the same V

167
Q

Chronic obstructive pulmonary disease (COPD) - individuals

A

Typically found in someone who smokes cigarettes

168
Q

Chronic obstructive pulmonary disease (COPD) - lungs

A

Hyperinflated lungs - don’t properly deflate
Flattened diaphragm
If too hyperinflated, have little ability to inflate their lungs since already somewhat inflated –> rapid and shallower breaths to compensate
Degrades elastin

169
Q

Fibrosis - compliance

A

Decreased compliance so need more energy to inflate lungs

170
Q

Fibrosis - risk factors

A

Can occur due to air pollutants

171
Q

Fibrosis - lungs

A 
Caused by an increase in collagen in lungs --> stiff lung
Deflated lungs
Mid-sternal space wide
Fluffy areas with fibrotic tissue
Speckled; white splotches
172
Q

The last air you breathe in is…

A

The first air you breathe out, so O2 of air you breathe out will be similar to atmospheric O2

173
Q

The last air you breathe out (at end of your exhale)… (O2)

A

It will have a significantly lower amount of O2 (~17%) because it originates further down your airway

174
Q

Highest point of resistance in respiratory zone

A

Upper airway (trachea) because X-sectional area of one trachea is less than that of ~300 million alveolar ducts

175
Q

Airflow at higher vs lower points of resistance

A

High R = less air flow = turbulent

Low R = high air flow = slow and laminar, unidirectional = good for gas exchange

176
Q

Physical factors controlling airflow

A

If start by blowing out all the air in our lungs, the airways are quite narrow / high R
As you begin to inhale maximally, the radial traction starts to pull open the airways until TLC

177
Q

Smooth muscles of bronchioles are covered in…

A

Receptors sensitive to nerves and hormones which are constantly modulating the diameter of the bronchioles

178
Q

ANS control of airway smooth muscle

A 
Parasympathetic nerves:
Originate from brainstem
Contained within the vagus nerve
Bronchoconstriction
ACh acts on muscarinic receptor

Sympathetic nerves:
Originate from levels of the spinal cord
Bronchodilater
NE acts on beta-adrenoceptors

179
Q

Asthma: What is salbutamol

A

A beta-adrenoceptor agonist

180
Q

Asthma: Inhaler

A

Contains salbutamol which mimics sympathetic NS activity
Acts on beta-adrenoreceptors on the smooth muscle in bronchioles to make them relax
Instant relief because drug goes directly where you want it to go

181
Q

Targeting drugs in lungs

A

Can target your drug directly where you want it to go

182
Q

Control of airway diameter and resistance - bronchioles - nerve fibres

A

Each bronchiole has nerve fibres that are stretch-sensitive

When bronchioles dilate during inhalation, it stretches mechanoreceptors –> send signals into brain

183
Q

Hering-Breuer Inflation reflex - Mechanoreceptors

A

Nerve fibres mechanically sensitive to distortion/inflation through the vagus nerve into the brainstem, which connect to the sympathetic NS (dilation)
Also terminates inspiration

184
Q

Pulmonary system - arteries

A

Blue

Feed alveoli

185
Q

_______ are wrapped around the alveoli

A

Capillaries

186
Q

Pulmonary system - veins

A

Bright red

Full of oxygenated blood to carry back to the heart

187
Q

Pulmonary vs systemic pressure

A

Pulmonary: 22/10 mmHg (mean 16 mmHg)
Systemic: 120/80 mmHg (mean 93 mmHg)

188
Q

Mean pressure = ?

A

SA of bottom third of triangle
DP + (1/3 x PP)
Where PP = SP - DP

PP = pulse pressure
SP = systolic pressure
DP = diastolic pressure
189
Q

Pulmonary circuit - high or low pressure

A

Low pressure, so blood from right ventricle comes here

190
Q

Complete circulation - time

A

~25s

191
Q

Where does blood to the pulmonary vascular bed originate from

A

The right ventricle

192
Q

Tracheobronchial circulation - contamination

A

Pulmonary vein carries oxygenated blood, but is contaminated by blood from the tracheobronchial circulation that bypasses the lung (‘anatomical shunt’)

193
Q

Two pulmonary circulations

A

One goes to alveoli

Other goes to tracheobronchial tree

194
Q

Tracheobronchial tree - origin

A

Comes off aorta

195
Q

What does the tracheobronchial tree receive blood from

A

Systemic circulation / aorta

196
Q

What does the tracheobronchial tree innervate

A

Trachea, bronchus and bronchioles

197
Q

Mean pulmonary artery pressure

A

16 mmHg

198
Q

Pulmonary artery, pulmonary capillaries and left atrium pressure

A

As pulmonary artery divides into smaller arteries and arterioles, the pulses become smaller - reduced R
Eventually the pulses fade at the pulmonary capillaries where blood flow is continuous/constant (not pulsatile)

199
Q

Sheet blood flow around alveoli

A

Capillaries are so dense that their walls touch each other, most of which vanish
Results in a sheet flow of blood interspersed by an interstitial tissue that pulls the capillaries tgt

200
Q

Sheet blood flow around alveoli - side walls

A

Erode away to form a flatter texture –> allows blood to be in more contact with the alveolar membrane

201
Q

Flow of blood in alveoli

A

Laminar (smooth)

202
Q

Pulmonary artery pressure and resistance

A

Increase in pulmonary artery pressure = decrease in pulmonary vascular resistance
Due to distension and recruitment

Opposite of systemic circuit

203
Q

Factors controlling blood flow in lungs

A

Physical

Hypoxia

204
Q

Factors controlling blood flow in lungs: Physical

A

Since blood vessels are attached to lung parenchyma, physical or passive mechanisms related to lung V alter size of vessel diameter

205
Q

Factors controlling blood flow in lungs: Hypoxia

A

A decreased O2 causes vasoconstriction via a direct effect
Limits blood flow to poorly ventilated alveoli
Hypercapnia also does this

206
Q

Hypoxemia

A

Decreased oxygen level

207
Q

Distension and recruitment

A

Distension: compliance / wider arterioles
Recruitment: more vessels (that were closed) now open –> resistance falls

208
Q

Pulmonary oedema

A

Where P in lungs gets too high –> fluid from capillaries is pushed out –> starts to fill up alveoli with interstitial fluid –> increases distance of diffusion of gases between blood and air

Prevented by keeping P low, and if it does increase, resistance decreases through distension and recruitment

209
Q

When does hypoxic vasoconstriction occur

A

If there is an inflammatory response

210
Q

What does hypoxic vasoconstriction result in

A

Increased R to airflow due to build up of mucous and fluid

Air follows pathway of least R, so will go into alveoli with wider duct

211
Q

Hypoxic vasoconstriction: Constricted alveoli

A

Partial pressure of constricted alveoli reduces –> hypoxic
Causes constriction of local arterioles feeding this alveolus because would not be optimal to send blood to alveoli with low oxygen - known as a physiological shunt as its redirected to alveoli with lots of oxygen

212
Q

There is better ______ at the base of the lung

A

Perfusion

213
Q

What is the regional variation in blood flow due to

A

Gravity - restricts the height blood can be pumped (i.e. hydrostatic pressure)

214
Q

What does hypoxic vasoconstriction increase

A

Increases dead space because the alveolus can no longer undergo gas exchange

215
Q

Does hypoxia always cause vasoconstriction

A

Only in the lungs - in other parts of the body it causes vasodilation

216
Q

Which part of the lung has highest blood flow

A

Bottom of lung has more blood flow than top

At top, there’s hardly any blood flow when you’re upright and at rest - due to gravity

217
Q

HP

A

Hydrostatic pressure

218
Q

P(v)

A

Venous pressure

Driving force for blood flow

219
Q

P(a)

A

Pulmonary blood arterial pressure

220
Q

P(A)

A

Alveolar pressure

221
Q

Lung - zones

A

Zone 1: Top of lung where HP is lowest so is poorly perfused P(A) > P(a) > P(v)
Zone 2: Middle of lung, pressure sufficient to open capillaries through the alveoli P(a) > P(A) > P(v)
Zone 3: Base of lung where HP is greatest so is best perfused P(a) > P(v) > P(A)

Form a continuum

222
Q

Gravity and lung size

A

Gravity is only a problem in animals and humans that are upright because gravity has a greater effect if you have larger lungs

223
Q

What does a high alveolar pressure cause

A

Alveolar pressure squashes down the vessel and prevents blood from flowing, e.g. in zone 1

224
Q

Parts of the lung - ventilation

A

Much better air ventilation at lower part than upper part of lung

225
Q

The bottom of the lung is better…

A

Perfused and ventilated

226
Q

Oxygen levels in lung just before inspiration

A

Lots of well-oxygenated blood at top of lung

Low levels of oxygen at bottom of lung because lots of blood flow which takes up the oxygen

227
Q

Ideal vs actual ventilation-perfusion ratio (VA/Q)

A

1; perfectly matches perfusion with ventilation
i.e. alveolar ventilation divided by CO

In reality, this ratio is 0.8

228
Q

Perfusion = ?

A

Q = CO = HR x SV = 5 L/min

229
Q

Disease states: Pulmonary hypertension

A

Right heart failure
Hypoxia = vasoconstriction
Causes oedema

Causes increase in hydrostatic P of pul cap - known as pulmonary oedema
Diffusion distance for O2 increases –> reduces efficiency of gas exchange –> breathlessness

230
Q

Disease states: Pulmonary oedema

A

Left heart failure - blood remains in left ventricle –> congestion –> increases pulmonary artery P –> oedema –> breathlessness - dyspnoea, particularly on exhaustion
Systemic hypoxia

231
Q

Factors regulating movement of gas across the respiratory surface

A 
Area
Thickness of tissue
Partial pressure differential across tissue
Solubility of gas in blood
Molecular weight of gas
232
Q

Factors regulating movement of gas across the respiratory surface: Area

A

Each alveoli ~0.3mm in diameter

In spherical, SA = 50-100 m^2 and V = ~4L

233
Q

Factors regulating movement of gas across the respiratory surface: Thickness of tissue

A

Only ~0.5µ alveolar membrane that separates blood from outside world
Contains surfactant, epithelial layer, interstitial layer, BM, endothelial cell

234
Q

Factors regulating movement of gas across the respiratory surface: Partial pressure differential across tissue

A

O2 from outside to inside: 60 mmHg
CO2 from inside to outside: 6 mmHg

Important for movement of gases from higher to lower areas of conc

235
Q

Factors regulating movement of gas across the respiratory surface: Solubility and molecular weight of gas

A

Solubility more important than MWt of gas
CO2 25x more soluble in blood than O2 and diffuses 0.86x faster than O2
But release time of CO2 from haemoglobin slower than O2, so balanced overall

236
Q

Factors controlling rate of rise of partial pressure of a gas in blood

A

Diffusion limited:
Includes rxn time for bonding with haemoglobin
e.g. CO

Perfusion limited:
Limit is the blood flow
e.g. N2O and O2

237
Q

Factors controlling rate of rise of partial pressure of a gas in blood: Increasing uptake for a perfusion limited gas

A

Can increase uptake if blood flow is greater

If you start exercising and need more O2, can increase blood flow to lungs and pick up oxygen

238
Q

Amount of time spent by RBC through the alveolus

A

Only spends 3/4 of a second through the alveolus

239
Q

How long does it take for blood to be saturated with oxygen and N2O

A

Within 1/4 of a second because diffusion is v quick

240
Q

CO rate of uptake

A

Very slow - if breathing it for a long time, will accumulate lots of CO
Diffusion limited - doesn’t bind v quickly to blood and takes a long time to cross the alveolar membrane

241
Q

CO poisoning

A

Takes a long time to get the CO off the haemoglobin molecule that it’s taken up - binding is slow

242
Q

Haemoglobin preference

A

Has a preference for CO over O2, so CO bounces the O off the haemoglobin –> extremely hypoxic

243
Q

How is oxygen transported in blood

A

Binds with haemoglobin (major pathway)

Dissolves in solution

244
Q

Haemoglobin (Hb) molecule - haem moiety

A

Each α and β polypeptide chain contain a binding site called a haem moiety - 4 within a Hb molecule, each of which can bind to a single oxygen

245
Q

Haemoglobin (Hb) molecule - allosteric effect

A

When first molecule of O2 binds onto a haem moiety, it twists the molecule to expose the next haem moiety etc.
This process is called cooperative binding

246
Q

Where is Hb contained within

A

Erythrocytes (RBCs)

247
Q

Why are RBCs important

A 
Concentrates Hb
Concentrates enzymes (e.g. carbonic anhydrase)
248
Q

What would happen if we didn’t have RBCs

A

Blood would be really think and difficult to pump around the body

249
Q

RBCs - structure

A

No nucleus

Biconcave - allows it to squeeze through capillaries at branch points

250
Q

Haemoglobin (Hb) molecule - binding of oxygen molecule

A

First molecule of O2 that binds to Hb molecule takes longer than second, which takes longer than third, then fourth

251
Q

Oxygen dissociation curve: Relationship

A

Sigmoidal relationship

Due to cooperative binding

252
Q

Oxygen dissociation curve: Systemic veins

A

Lower affinity for O2 at lower P(O2)s

Encourages O2 release at tissues

253
Q

Oxygen dissociation curve: Systemic arteries

A

Higher affinity for O2 at higher P(O2)s

Encourages O2 uptake at lungs

254
Q

Oxygen dissociation curve: Percent of O2 unloaded by haemoglobin to tissues

A

~25% saturation
i.e. as you move form higher to lower P(O2), there’s an unloading O2; the Hb can’t be saturated as much because it loses some of its affinity to bind oxygen at lower pressure

255
Q

Oxygen dissociation curve: Affinity at alveoli

A

Affinity must be strong when it goes back to alveoli to pick up oxygen - want maximal affinity in lung

256
Q

Deoxyhaemoglobin and oxyhaemoglobin

A 
Form of Hb without oxygen
Hb4 + O2 --> Hb4O2
Hb4O2 + O2 --> Hb4O4
Hb4O4 + O2 --> Hb4O6
Hb4O6 + O2 --> Hb4O8 - oxyhaemoglobin (fully saturated)
257
Q

CO2 from tissues

A

CO2 + H2O H2CO3 H+ + HCO3-
This H+ then goes into this reaction:
Hb4O8 + H+ Hb4 + 4O2 –> to tissues

258
Q

Hb affinity - acidity

A

In an acidic environment, Hb has less affinity for O2

259
Q

Tissues vs lungs - oxygen

A

At tissues, more CO2, lower pH –> O2 is released

At lungs, less CO2, higher pH –> O2 is taken up

260
Q

What is one of the main reasons haemoglobin loses its affinity for oxygen

A

The acidity produced from H+ (reduction in pH) at level of tissues

261
Q

Total oxygen conc in blood = ?

A

Oxygen bound to Hb + oxygen dissolved in plasma

262
Q

Amount of oxygen dissolved in plasma

A

~0.5 mL / 100mL of blood

263
Q

Amount of oxygen dissolved in plasma at 100% oxygen

A

Increases oxygen in plasma up to ~2mL / 100mL because you increase the diffusion gradient between the alveoli and the blood

264
Q

Anaemia

A

If individual lost half their blood, it reduces the amount of oxygen content in blood by half (both arterial and venous)
But if look at blood saturation, remains at 100% because Hb that remains can still fully load up with O2

265
Q

Oxygen dissociation curve: Bohr shift

A

For a given PO2, more oxygen is given up
Due to increased CO2, H+, temp, DPG –> lower affinity of Hb for O2 in venous blood
e.g. at tissues

266
Q

Oxygen dissociation curve: Leftward shift

A

For a given PO2, oxygen sat is increased
Due to reduced CO2, H+, temp, DPG —> increases affinity of Hb for O2 in venous blood
e.g. at lungs

267
Q

Oxygen dissociation curve: Fetal haemoglobin

A

Higher affinity for oxygen at a given level of PO2

Helps movement of oxygen across placenta to fetus

268
Q

Oxygen dissociation curve: What happens if fetal Hb doesn’t have higher affinity for oxygen

A

It wouldn’t be able to draw the oxygen from the mother’s blood into its own

269
Q

Oxygen dissociation curve: Myoglobin

A

Large affinity for oxygen

Stores O2 in body, particularly in skeletal muscle, where it can be used under conditions of low O2 –> releases this O2

270
Q

How is CO2 transported in blood

A

Dissolves in solution (CO2 aq)
Chemical in form of HCO3-
Combines to amine groups (NH2)
As H2CO3 and CO3- ions

271
Q

CO2 vs O2 solubility

A

CO2 solubility in blood is 20x higher than O2

272
Q

CO2 transport in blood - %

A

Plasma 70%, RBCs 30%

273
Q

CO2 transport in blood: Slowly vs rapidly formed bicarbonate

A

Slowly formed occurs without an enzyme in plasma (5%)

Rapidly formed occurs with an enzyme in RBCs (20%)

274
Q

Most bicarbonate in the plasma is formed by…

A

An enzyme called carbonic anhydrase

275
Q

CO2 transport in blood: Chemical in form of HCO3- - equation

A

CO2 + H2O H2CO3 H+ + HCO3-

276
Q

Where is carbonic anhydrase found

A

In RBCs

277
Q

CO2 transport in blood: Amine groups - equation

A

CO2 + R-NH2 R-NHCOO- (carbamino protein) + H+

where R can be Hb

278
Q

__x more Hb than any other plasma protein

A

4

279
Q

What does Hb have greatest affinity for

A

Greater affinity for CO2 than other plasma proteins

280
Q

Hb - buffer

A

Acts as a buffer to maintain pH

Essential for optimal running of enzymes, e.g. carbonic anhydrase

281
Q

CO2 dissociation curve: what does it depend on

A

P(CO2)

282
Q

CO2 dissociation curve: shape

A

Linear over physiological range of P(CO2)

Very steep - highly sensitive

283
Q

CO2 dissociation curve: saturation

A

No saturation as CO2 is v soluble in plasma

284
Q

CO2 dissociation curve: Greater affinity for CO2 when pH is _____

A

Lower

285
Q

CO2 dissociation curve: _____ blood has greater affinity for CO2

A

Venous

286
Q

CO2 dissociation curve: Haldane effect

A

The difference between venous-arterial blood

Enhances unloading of CO2 from tissues into blood

287
Q

CO2 dissociation curve: Haldane effect - PO2

A

Lower PO2 –> greater affinity for CO2 (tissues)

Higher PO2 –> reduced affinity for CO2 (lungs)

288
Q

Hypoxia

A

Low levels of oxygen

289
Q

Anoxia

A

No oxygen

290
Q

Asphyxia

A

Deprived of oxygen

291
Q

Hypercapnia

A

High CO2

292
Q

Hypocapnia

A

Low CO2

293
Q

Hyperventilate

A

Excessive breathing

Decreases PCO2, increases PO2

294
Q

Hypoventilate

A 
Shallow breathing (inadequate)
Increases PCO2
295
Q

Ischaemia

A

Inadequate blood supply to an organ

296
Q

Apnoea

A

No breathing

297
Q

Dyspnoea

A

Sensation of breathlessness

298
Q

Fainting

A

An important mechanism because it puts your brain at the same level as your heart –> less effect of gravity

299
Q

What are chemoreceptors

A

Blood gas detects that control breathing

300
Q

Types of chemoreceptors

A

Peripheral chemoreceptors - located near major blood vessels

Central chemoreceptors - located within medulla

301
Q

Main peripheral chemoreceptor

A

Carotid body chemoreceptors

302
Q

Location of carotid chemoreceptors

A

Located at bifurcation of common carotid artery in neck
Sits in the crux where internal and external carotid arteries originate
Close to baroreceptors (but not the same)

303
Q

Carotid chemoreceptors - sinus nerve

A

Joins the glossopharyngeal nerve, then to medulla (brainstem)

304
Q

Location of central chemoreceptors

A

3 ‘chemo-sensitive’ regions on the ventral surface of the medulla oblongata

305
Q

What stimulates peripheral chemoreceptors

A 
Hypoxia (reduced PO2)
Hypercapnia (increased PCO2)
Haemorrhage (low O2)
Acidosis
Increased sympathetic activity
Sodium cyanide (experimental tool)
306
Q

Acidosis

A

Decreased blood ph

307
Q

Peripheral chemoreceptors - response time

A

Fast - within a breath

308
Q

What stimulates peripheral chemoreceptors - sodium cyanide

A

Temporarily switches off ETC

Similar to low O2

309
Q

Central chemoreceptors - response time

A

Slow
~30s
Because there is limited carbonic anhydrase in CSF

310
Q

Central chemoreceptors: CO2

A

Can cross blood-brain barrier

311
Q

Central chemoreceptors: Blood-brain barrier

A

Effectively the endothelial cells that line the capillaries

312
Q

Central chemoreceptors: CSF

A

Within the CSF there is some carbonic anhydrase

313
Q

Central chemoreceptors: Neural cells

A

Very close to CSF, so if you apply acid, they become v activated and stimulate breathing

314
Q

Central chemoreceptors: Brain is intrinsically sensitive to ___

A

H+

315
Q

What predominantly simulates central chemoreceptors

A

H+ ions

316
Q

Central chemoreceptors: H+

A

Can’t cross blood-brain barrier since charged

317
Q

Central chemoreceptors: CO2 vs O2

A

Only respond to CO2 (H+) - don’t respond to low oxygen

318
Q

Ventilatory response to hypoxia involves what chemoreceptors

A

Peripheral chemoreceptors only

319
Q

Ventilatory response to hypoxia

A

As PO2 is reduced, minute ventilation increases (slowly then dramatically) until peak
Ventilation starts to slow due to central depressant effect within brainstem
Cells within brainstem that are depressed eventually stop functioning –> depresses breathing –> apnoea

320
Q

Ventilatory response to hypoxia - gasping

A

Individual gasps a number of times

The last attempt to auto-resuscitate

321
Q

Ventilatory response to hypercapnia involves..

A

Mediated by:
Central chemoreceptors 80%
Peripheral chemoreceptors 20%

322
Q

Ventilatory response to hypercapnia - slope

A

Steep slope - exquisitely sensitive to CO2

Increased PCO2 = steep increase in minute ventilation

323
Q

Ondine’s curse

A

No central chemoreceptors means you can die in your sleep

Very important for breathing

324
Q

What allergens are associated with asthma

A

Pollen

Dust

MEDSCI 142 (9 decks)

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