L5 Physiology of the Airway Flashcards
Why do people snore?
Snoring is the result of the relaxation of the uvula and soft palate.[11] These tissues can relax enough to partially block the airway, resulting in irregular airflow and vibrations. Snoring occurs in 25% of the population.
What is sleep apnea?
Sleep apnea occurs in 10% of the population. In sleep apnea, patients stop breathing when they are sleeping causing them to wake up. When breathing normally the ribcage and the abdomen work together however when breathing is abnormal, they work against each other. The point at which they wake up again is an arousal.
These patients snore a lot and get sleepy during the day. They spend there entire night dozing as when they wake up, they go into stage 1 or 2 of sleep. This means they are constantly tired. Once they reach deep sleep, they stop breathing and wake up.
What is the difference between tonic and phasic muscle?
Tonic muscle activity produces tone. This is permeant activity that holds the muscle in place.
Phasic activity is muscle activity that comes in phases. For example, activity that only occurs during inspiration or expiration.
When is the control of muscles poor?
Sleep, under the influence of alcohol, under anaesthetics or under the influence of sedatives.
What is the shape of ciliated epithelia at the level of the:
(i) Nose and Pharynx
Psuedo-stratifed columnar epithelium
What is the shape of ciliated epithelia at the level of the:
(ii) Trachea and bronchi
Columnar epithelium
What is the shape of ciliated epithelia at the level of the:
(iii) Bronchioles
Cuboidal epithelium.
The epithelial cells become narrower and narrower before merging with the epithelial cells. At level of the bronchioles they lose their cilia.
What is the function of goblet cells?
To secrete mucin.
When do goblet cells increase secretion?
When there are things that irritate the lungs present such as tobacco smoke or an infection.
What is the structure of airway lining fluid?
There is a pericillary layer next to the epithelium. This is a salt water layer. The epithelium pump out chloride ions followed by sodium ions drawing out water. The cilia live within this layer.
Above the pericillary layer is a gel layer made of mucus. This is a thick, viscous layer. The purpose of this is to catch things that are inhaled.
What is the name of the stroke cilia perform to sweep mucus out of the way?
Effective stroke. Every so often, the cilia will reach out into the gel layer and pull the mucus along before retiring back to the pericillary layer to perform a recovery stroke. There are millions of cilia in our airways moving mucus along at a rate of approximately 4mm/min.
What is the purpose air airway lining fluid?
- Humidification of air. Air must be humidified before reaching the alveoli or it will cause the alveoli to dry out and not function. The water inter airway lining fluid will evaporate and incorporated into inhaled air, humidifying it.
- Defence. The mucus will trap pathogens and particulate matter. This will then be wept up by the Cilla and move up the airways where it can either be swallowed (and destroyed by the stomach) or coughed up.
What is the heat and moisture exchange?
As you breath in, the mucosa warms and humidified the air. When you breath out, the air coming out is now warmer and humidified compared to the mucosa and so water condenses back into the mucosa. This means you don’t use that much water during breathing - you only lose 120 - 150ml in expired air. Since it evaporates on the way out, you don’t lose litres of water.
What are the symptoms of cystic fibrosis?
People with CF can have a variety of symptoms, including:
- Very salty-tasting skin.
- Persistent coughing, at times with phlegm.
- Frequent lung infections including pneumonia or bronchitis.
- Wheezing or shortness of breath.
- Poor growth or weight gain in spite of a good appetite.
- Male infertility
- Diabetes
- Loss of pancreatic function
- Fatty stools
What is the prevalence of cystic fibrosis?
1 in 25 have the gene for it. It is an autosomal recessive inherited disease. This leads to cystic fibrosis being in 1 in 2500 births.
What is the cause of cystic fibrosis?
Cystic fibrosis is due to an abnormal CFTR Cystic fibrosis transmembrane regulator. This is a protein on epithelial cells that controls the airway lining fluid by controlling chloride secretion. The channel is not functioning and so chloride ions are not secreted into the fluid, means water is not drawn out. The secretion becomes too viscous for the cilia to move and so the individual becomes very prone to chest infections.
At what particle size, are inhaled particles deposited on the nose and pharynx? How is this achieved?
Greater than 8 microns e.g. pollen.
The particle has enough inertia, so that when the air turns a corner in the airway, the particle drops out and gets trapped on the pharynx.
(Inertia is the resistance of the object to any change in its motion, including a change in direction.).
At what particle size, are inhaled particles deposited on the large airways? How is this achieved?
3-9 microns. This includes fungal spores which can get into the large airways. These mode also works via inertial impaction.
At what particle size, are inhaled particles deposited on the small airways? How is this achieved?
0.5-3 microns
The size of small particles makes it drop out the air and sediment at the bronchioles. Particulate matters, stone dust and asbestoses do so.
At what particle size, are inhaled particles deposited on the alveolus? How is this achieved?
Particles less than 0.5 microns. These particles are able to diffuse and move via Brownian motion. This includes small (including cigarette smoking), which along with other very small particles, is usually exhaled.
What are the non-immunological defences to pathogens in the lungs?
- Physical barrier - catch on the mucous and cough it out/swallow and the enzymes in the stomach destroy it. Physical removal is how we deal with 99% of inhaled particles. The mucin stops the pathogens getting through the gel and into the cells, leading to an infection.
- Chemical inactivation - lysozymes, protease enzymes e.g. elastase, antimicrobial peptises e.g. human beta defensins (proteins produced by the epithelia that are antibiotics and kill common bacteria). The lungs produce anti-proteases as well to prevent the proteases from damaging the cells in the case they get through the mucus into the lung epithelia. These are all chemicals produced by the epithelia found in the mucous layer.
Alveolar macrophages - The macrophages have left the body tissue looking for pathogens that may have, by chance, stuck to the alveolus. The macrophages are there to engulf them to prevent infection.
- Chemical inactivation - lysozymes, protease enzymes e.g. elastase, antimicrobial peptises e.g. human beta defensins (proteins produced by the epithelia that are antibiotics and kill common bacteria). The lungs produce anti-proteases as well to prevent the proteases from damaging the cells in the case they get through the mucus into the lung epithelia. These are all chemicals produced by the epithelia found in the mucous layer.
What are the immunological defences to pathogens in the lungs?
Humoral:
IgA - found in the nose and large airways.
IgG - found in the small airways.
IgE - found in allergic disease
Cell-mediated response:
- Epithelial cells have can recognise pathogens in the area and so release cytokines to initiate an inflammatory response.
Macrophages can also digest pathogens. Neutrophils (infection) and eosinophils (allergy) also act as phagocytes.
What does inhalation of nitrates lead to?
Inhalation of nitrates can make asthma worse and can cause airway irritation.
What does inhalation of particulate matter lead to?
Inhalation of particulate matter can cause damage in the long term. It can lead to lung and systemic inflammatory responses; asthma, pneumonia, stroke, heart attack and type II diabetes.
