Physiology of the Airway Flashcards
What are present in the mucosa of the airway?
Pressure receptors
What nerve do receptors send impulses up when the pressure in the airway drops? What occurs after this?
An afferent nerve –> trigeminal nerve
What are afferent nerves?
Carry sensory information from the body to the CNS (brain)
Where do afferent fibres go?
Into the brainstem where information is processed
Where is the message sent after leaving the brainstem?
Sends efferent message down the vagus nerve to the muscles
What is effect of this impulse after drop in pressure of airway?
Makes muscles contract more so pressure changes
Describe basic pathway during drop in pressure
Pressure receptors –> Brainstem –> Pharyngeal muscle contraction
What controls pharyngeal muscle contraction?
Afferent (trigeminal) nerve
The brain controls muscles in the airway in response to what?
Changes in airway pressure
What can slow down reflexes and make airway control less efficient?
Sleeping, alcohol, anaesthetics
What % of the population suffers with snoring?
25%
What occurs during snoring?
Physiological slowing of the pharyngeal dilator reflexes, soft palate flaps as air tries to flow past it
What % of the population suffers with sleep apnoea?
10%
What is sleep apnoea?
Disorder where person has pauses in breathing or periods of shallow breathing during sleep (can last from few seconds to few minutes) –> diagnosed as number of times person stops breathing for 10 seconds or longer
What are clinical features of sleep apnoea?
Snoring, daytime somnolence, associated with obesity and hypertension
How can obesity lead to sleep apnoea?
Fat in neck tissue makes airway narrower
What is treatment for sleep apnoea?
- Weight loss
2. CPAP
How does CPAP work?
Ventilator sticks in patients nose and blows gas down nose to keep airway pressure above atmospheric to stop it collapsing
What is needed to keep airway patent?
Continuous muscle activity
What is airway lining fluid produced by?
Ciliated epithelial cells and goblet cells
What shape are epithelial cells in:
- Nose and pharynx
- Trachea and bronchi
- Bronchioles
- Pseudostratified
- Columnar
- Cuboidal
What happens to epithelial cells as you move further down the airways?
They get flatter and flatter until they merge with the alveolar cells
Somewhere just beyond bronchioles they lose their ccilia
Where are the goblet cells?
In amongst the epithelial cells
What are goblet cells full of? What is purpose of this?
Mucin –> protects lungs
What are mucin granules released in response to?
- Airway irritation
- Tobacco smoke
- Infection
What 2 layers does airway lining fluid form?
- Periciliary layer
2. Mucous layer
Where is the periciliary layer?
Next to the cell (water layer)
Where is the mucous layer?
Above the periciliary layer (gel layer)
What is function of airway lining fluid?
Catches any dirt from air. Cilia then moves airway lining fluid along and is removed by lungs
What layer are cilia found in and why?
Live within periciliary layer –> not viscous so can move around
What motion do cilia move in?
Effective stroke and recovery stroke
What are cilia inhibited by?
- Tobacco smoke
- Inhaled anaesthetics
- Air pollution
- Infections
Why is smoker’s cough worse in the morning?
During night cilia begin to work again and move mucus towards larynx
How is airway lining fluid involved in humidification?
Heat and water evaporate from fluid and humidifies gases as they are inhaled
Heat and water go back into the mucosa during exhalation (prevents losing too much water)
What is purpose of air humidification?
Stops alveolar cells drying out
Why is nose breathing better than mouth breathing?
Air has further to travel so more exposure to fluid
Describe changes in thickness of periciliary and mucous layer?
Periciliary –> Always remains same thickness
Mucous layer –> Changes thickness depending on air moisture
What is CF caused by?
Abnormality of cystic fibrosis transmembrane regulator (CFTR) protein
Fluid becomes more viscous and cilia struggle to move –> prone to chest infections
What is the CFTR protein?
Protein on epithelial cells that controls salt from airway lining fluid
Why do big inhaled particles not enter the lungs?
Have enough weight to carry on and stick to back of pharynx instead of turning corner
Captured by mucosa in the upper airway
What makes smaller inhaled particles drop and stick to bronchioles?
Airflow in bronchioles is slow
What determines where an inhaled particle is deposited?
The size of the particle
Where are smaller particles often deposited?
Alveoli –> may be used to influence inhaled drug deposition
How is the gel layer effective as a pulmonary defence?
Prevents pathogens getting through to epithelial cells below
What non-immunological systems are involved in pulmonary defence?
- Physical barrier
- Removal of pathogens
- Chemical inactivation (lysosomes, protease enzymes, antimicrobial peptides)
- Alveolar macrophages
How are alveolar macrophages involved in pulmonary defence?
Engulfs dust, pathogens and other particles found in alveolus
Where is IgA/IgG/IgE found in regards to pulmonary defence?
IgA –> Nose and large airways
IgG –> Small airways
IgE –> Allergic disease
How is humoral system involved in pulmonary defence?
- Inhibit binding of pathogens
- Complement activation
- Recruitment of immune cells
How is cell-mediated system involved in pulmonary defence?
- Epithelial cells can recognise pathogens and release cytokines
- Macrophages
How many deaths per year in UK are attributable to air pollution?
40,000
What can inhaling particulate matter result in?
Lung and systemic inflammatory response
What can inhaling nitrous oxides result in?
Airway irritation and asthma
What can inhaling ozone result in?
Airway irritation and cough
