Airway physiology

Question 1

Which 2 main muscles keep the airway open?

Answer 1

Genioglossus and the tensor palati

Question 2

Which two nerves are involved in the pharyngeal dilator reflex?

Answer 2

Trigeminal nerve (afferent: pressure receptors –> brain stem) and vagus nerve (efferent: brain stem –> pharyngeal muscle contraction)

Question 3

Why does snoring occur?

Answer 3

The brain is not active enough to keep the airway fully open so the soft pallate flaps against the pharynx

Question 4

What is sleep apnoea?

Answer 4

The airway is not open at all for a time so trouble breathing and deep sleep is impossible. Adrenaline is released when can’t breathe which can lead to hypertension etc.

Question 5

What are two treatments for sleep disordered breathing?

Answer 5

Weight loss and CPAP (continuous positive airway pressure)

Question 6

What is required to keep the airway patent?

Answer 6

Continuous muscle activity

Question 7

Which cells produce airway lining fluid?

Answer 7

Goblet cells

Question 8

What three things might cause excess mucin granules (mucus) to be released?

Answer 8

Airway irritation, tobacco smoke, infection

Question 9

What structures move the mucus through the lungs?

Answer 9

Cilia

Question 10

What are four things that inhibit the movement of cilia?

Answer 10

tobacco smoke, inhaled anaesthetics, air pollution, infections

Question 11

Why does smokers cough get worse at night/early morning?

Answer 11

Smoking paralyses the cilia, no cigarettes for a time overnight so the cilia start to recover which mobilises the mucus and causes the cough. Another cigarette in the morning paralyses them again and makes the cough better.

Question 12

What are two functions of airway lining fluid?

Answer 12

1. humidification

2. airway defence (bacteria is trapped in the mucus and escalated (muco-ciliary escalator) for expectoration)

Question 13

Which protein is affected in cystic fibrosis?

Answer 13

CFTR (cystic fibrosis transmembrane regulator)

Question 14

What are the two layers of airway lining fluid?

Answer 14

Periciliary and mucous

Question 15

Where are inspired particles >8µm deposited and by what mechanism?

Answer 15

Nose and pharynx by inertial impaction

Question 16

Where are inspired particles 3-8µm deposited and by what mechanism?

Answer 16

Large airways by inertial impaction

Question 17

Where are inspired particles 0.5-3µm deposited and by what mechanism?

Answer 17

Bronchioles by sedimentation

Question 18

Where are inspired particles >0.5µm deposited and by what mechanism?

Answer 18

They are fully inhaled and exhaled, diffusion

Question 19

Where in the respiratory tract would you want an inhaled hayfever drug to be deposited, and so what size particle would you want?

Answer 19

In the pharynx and large airways, so a large particle size >5µm

Question 20

Where in the respiratory tract would you want an inhaled asthma/COPD drug to be deposited, and so what size particle would you want?

Answer 20

In the small airways, so medium sized particle about 1-3µm

Question 21

Where in the respiratory tract would you want an inhaled drug to be deposited if you want it to be absorbed into the blood? What is a potential use for this and what sized particle is needed?

Answer 21

Alveoli, potential for insulin inhaler for diabetics, very small particle size 0.5-1µm

Question 22

What are the two types of pulmonary defence?

Answer 22

Non immunological and immunological

Question 23

What are the 3 components of non-immunological pulmonary defence?

Answer 23

1. Physical barrier and removal
2. Chemical inactivation
3. Macrophages

Question 24

What are 3 possible defences in the chemical inactivation non-immunological response?

Answer 24

1. Lysozymes
2. Protease enzymes (e.g. elastase)
3. Antimicrobial peptides (e.g. human beta defensins)

Question 25

What are the possible defences in immunological defence?

Answer 25

1. Humoral (IgA, IgG, IgE)

2. Cell mediated (epithelial or macrophages)

Question 26

What are the actions of the immunoglobulins in the humoral immunological defence system?

Answer 26

1. Inhibit binding of pathogens to epithelial cells
2. Complement activation
3. Recruitment of immune cells

Question 27

What is the role of the genioglossus and tensor pallati muscles?

Answer 27

Keep the airway open

Question 28

What is the role of the trigeminal and vagus nerve in the context of breathing?

Answer 28

Pharyngeal dilator reflex