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SGUL - Physiology 1 > Pulmonary Defence Mechanisms > Flashcards

Pulmonary Defence Mechanisms Flashcards

1
Q

How much oxygen is consumed by a human per day?

A

500 litres

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2
Q

How much oxygen is inhaled from the atmosphere by a human in a day?

A

8000 litres

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3
Q

What is the consequence of the high volume of oxygen inhaled?

A
  • Makes the respiratory system a major site of contact between internal structures of body and atmosphere
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4
Q

Name two things that movement of oxygen from the atmosphere to internal structures, requires.

A

Fast movement of air in and out of lungs
Efficient gas exchange

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5
Q

What does the fast movement of air put limits on?

A

Limits on surfaces that have filtering and barrier properties

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6
Q

What does efficient gas exchange require?

A
  • Large surface area
  • Warm environments to allow for diffusion
  • Innervation by blood vessels
  • Thin membrane at gas-blood interface
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7
Q

What specific conditions make the respiratory system immunologically vulnerable?

A
  • Thin membrane - delicate and vulnerable to damage
  • Warm environments - good environment for microorganisms to thrive
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8
Q

Outline the types of harmful organisms commonly found in the air.

A
  • Microorganisms
  • Allergens - e.g dust, pollen
  • Toxic gases
  • Pollution
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9
Q

Give examples of large particulates found in the air

A
  • Food
  • Choke hazards
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10
Q

Give examples of fine particulate matter found in the air

A
  • Pollution
  • Dust
  • Pollen
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11
Q

Give examples of pathogens found in the air

A
  • Bacteria
  • Viruses
  • Fungi
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12
Q

Outline three ways a respiratory condition can be transmitted

A
  • Droplet transmission
  • Breathing
  • Coughing
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13
Q

How can respiratory infections be distinguished?

A
  • Type and identity of microorganism
  • Respiratory structure affected
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14
Q

How do allergens such as dust and pollen, usually harm the respiratory system?

A
  • Trigger extreme immune responses
  • Causes local inflammation and tissue pathology
    EXAMPLE: airway narrowing and obstruction
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15
Q

Some organic particles, when inhaled, can cause chronic restrictive conditions.

With an example of a condition, suggest how they do this.

A

EXAMPLES: fibrosis, pneumoconiosis
- Cause particle deposition on the respiratory structures
- Trigger inflammation

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16
Q

Give examples of physical obstructions that enhance immunological defence of the lungs and airways.

A
  • Cilia
  • Mucus
  • Nasal hair
  • Branching structure of the airways
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17
Q

Give examples of protective reflexes that enhance immunological defence of the lungs and airways.

A
  • Coughing
  • Expiratory reflex
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18
Q

Give examples of immune cells that enhance immunological defence of the lungs and airways.

A
  • Antimicrobial proteins
  • Innate immunity/epithelial cells
  • Resident immune cells e.g macrophages
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19
Q

What are the usual roles of physical adaptions in immunological defence?

(FPATH RECAP)

A
  • Prevents particles and microorganisms reaching a certain target
  • With the respiratory system, it prevents them reaching the airways, lungs and bloodstream
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20
Q

What are the roles of the nasal hairs in the first 1cm of the nasal passage?

A
  • Filters out large particles (>10μm) present in the air.
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21
Q

Briefly outline the structure of the nasal turbinates.

A
  • Lined with mucous membranes
  • Found in the nasal cavity after the nasal hairs
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22
Q

Briefly outline the structure of the nasal turbinates.

A
  • Humidifies air before it reaches the lungs
  • Further filtration of particles larger than ≈ 2μm
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23
Q

What can cause decreased nasal hair density/increased mouth breathing?

What is the effect of decreased nasal hair density/increased mouth breathing?

A

CAUSE: Upper respiratory occlusion
EFFECT: Greater risk of asthma

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24
Q

Where is mucus produced?

A

Submucosal glands and goblet cells

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25
Q

What is the purpose of mucus?

A

Traps inhaled particles

26
Q

Outline the composition of mucus

A
  • Gel with elastic and viscous properties - made up of water and solids(such as mucin, proteins and lipids)
  • Lysozyme
  • Antimicrobial proteins
27
Q

What is the mucus gel layer found on top of?

A

Periciliary layer

28
Q

Why is maintaining a sufficient periciliary layer depth important?

A
  • The layer provides a media in which the cilia can function i.e for mucociliary clearance
29
Q

What is the effect of coordinated beating of the cilia?

A
  • Produces wave of movement
  • This wave propels mucus gel layer towards the pharynx and allows it to be expelled
30
Q

Each cilia’s movement consists of a reverse stroke as well as a forward stroke. Yet the mucus gel layer will ONLY move in one direction. Suggest a reason why.

A
  • Cilia only makes contact with gel layer in forward stroke
  • During reverse stroke, cilia bends and tip passes UNDER the gel layer
  • Contact means layer will always move forward in one direction
31
Q

What are the characteristics of healthy mucus?

A
  • Clear colour
  • Easily cleared
32
Q

Why might mucus turn green following respiratory infection?

A
  • Due to breakdown of granulocytes
33
Q

Why might airway pathology change mucus viscosity?

A
  • Breakdown of surrounding epithelium
  • Mucus dehydration/ poor clearance - seen in cystic fibrosis
34
Q

Outline two factors that can regulate the level of mucus synthesised and secreted into airways.

A
  • Parasympathetic nervous system stimulation (e.g cholinergic activation of submucosal glands)
  • Local inflammation
35
Q

What is the effect of excessive mucus secretion?

A
  • Airway obstruction
  • Limited airflow
36
Q

How does cystic fibrosis trigger reduced mucociliary clearance?

A
  • CFTR Mutation
  • Mucus dehydration
  • Cilia dysfunction therefore reduced clearance
37
Q

How does chronic bronchitis trigger reduced mucociliary clearance?

A
  • Tobacco smoke exposure
  • Airway inflammation
  • Cilia damage and goblet cell hyperplasia therefore reduced clearance
38
Q

What are the effects of reduced mucociliary clearance?

A
  • More recurrent respiratory infections
  • Greater inflammation and tissue damage
  • Airway dysfunction and obstruction
39
Q

What is the main purpose of neural reflexes within the airways?

A
  • Trigger rapid expulsion of air
  • Deposition of particles
40
Q

What is the main purpose of neural reflexes within the airways?

A
  • Trigger rapid expulsion of air
  • Deposition of particles
41
Q

Give three examples of the reflexes within airways

A
  • Sneezing
  • Coughing
  • Laryngeal expiratory reflex
42
Q

What is the basic mechanism for the reflexes within the airways?

A
  • Activation of nociceptors by physical/chemical stimuli
  • Activation of afferent sensory neurones - transmit impulse to respiratory centres e.g the medulla
  • Efferent signals via parasympathetic/motor neurones transmitted to respiratory muscles (e.g diaphragm, intercostal muscles), the glottis (to close/open windpipe) and the airways. These muscles contract.
  • Causes rapid expulsion of air
43
Q

What is the difference between afferent and efferent nerve fibres?

A
  • Afferent fibres transmit signals to the CNS, efferent transmits away from CNS
44
Q

Outline the steps involved in sneezing

A
  • Stimulation of sensory receptors within nasal cavity
  • Deep inspiration phase
  • Compression phase - glottis closes, so pressure increases
  • Expiration phase - air is expelled
45
Q

Outline the phases involved in coughing

A
  • Stimulation of receptors within larynx
  • Deep inspiration phase
  • Compression phase
  • Expiration phase - air is expelled
46
Q

How does coughing differ from sneezing?

A
  • Coughing can be voluntary
  • Coughing also involves bronchoconstriction to increase expulsion pressure
47
Q

How does the laryngeal reflex differ from coughing?

A

No preceding inspiration phase

48
Q

What is the laryngeal reflex triggered by?

A

Activation of sensory receptors within vocal folds

49
Q

What is the role of the laryngeal reflex?

A

Prevent entry of foreign bodies into the airways

50
Q

What type of muscles are the following?
- GLOTTIS
- DIAPHRAGM
- INTERCOSTAL MUSCLES
- AIRWAYS

How are efferent signals transmitted towards these muscles?

A
  • Airways - smooth muscle - transmit via parasympathetic neurones
  • Glottis, diaphragm and intercostal muscles are skeletal muscle - transmit via motor neurones
51
Q

How does the branching structure of the airways assist airway filtration?

A
  • Airflow changes from laminar to semi-turbulent
  • Greater particle deposition
  • Greater contact between particles and mucus walls of airways
52
Q

What are the roles of resident immune cells in the airways?

A
  • Coordination of immune responses
  • Removal of deposited cells
53
Q

Where do alveolar macrophages derive from?

A

Progenitors produced in bone marrow

54
Q

Where are alveolar macrophages found?

A

Airspaces
- So can travel between alveoli

55
Q

What are the role of alveolar macrophages in phagocytosis?

A
  • Phagocytose pathogens, dead cells and foreign material
  • Digest these into residual material - removed by lymphatic system
56
Q

Some particles such as asbestos fibers cannot be cleared by digestion and so cause inflammation.

How do macrophages respond to this?

A
  • Toll-like receptor stimulation occurs
  • Triggers further inflammation and adaptive responses by secreting cytokines and other inflammatory mediators
57
Q

What is something that most macrophages can do, that alveolar macrophages don’t have the capacity to do?

A
  • Most macrophages can form antigen-presenting cells
  • Alveolar macrophages have very little capacity to do so
58
Q

What is the result of Toll-like receptor stimulation?

A
  • Initiates intracellular response
  • Leads to proinflammatory response (e.g cytokine release)
59
Q

What was determined from studies on mice with alveolar macrophage deficiencies?

A
  • Increased biomarkers of infection
  • Reduced survival following infection with pathogens
60
Q

Why must the activity of the immune system be regulated?

A

Damage can be caused to airways by excessive inflammation

61
Q

What type of bacteria lines the mucosal surfaces of the respiratory system?

A

Commensal bacteria

62
Q

What is the current understanding of the role of commensal bacteria?

A
  • Resist infection by other pathogens
  • Development/modulation of healthy immune system

SGUL - Physiology 1 (68 decks)

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