Which region of the brain is the respiration centre found?
The respiration centre is found in the reticular substance of the medulla oblongata and pons.
What are the physiological consequences of emphysema?
- Hyperinflation due to airway collapse & gas trapping
- Loss of capillary bed
- Reduced blood flow through the lungs
- Pulmonary hypertension
- Cor pulmonale
What is the atmospheric pressure at sea level? (In mmHg or kPa)
760mmHg or 101.1 kPa
What structure closes the gap caused by the incomplete tracheal cartilage rings?
Trachealis muscle; dense fibrocollagenous ligament rich in elastic fibres and smooth muscle.
What is the main driving force of respiration in a healthy individual?
Arterial pH, which is closely associated to partial pressure for CO2.
What percentage of the cell population are type 1 pneumocytes and how many are type 2?
- Type 1 = 40%, but 90% of the surface lining
- Type 2 = 60%
What is the treatment of mild COPD?
- Antimuscarinic such as ipratropium
- β2 agonist such as salbutamol.
Both are given as required
What is the treatment for severe COPD?
- Inhaled steroid
Consider steroid trail and home nebulisers.
Where in the lung is the best perfusion (volume of bloodflow) of the alveoli, when the person is standing?
The bases of each lung
What type of epithelium is found within the trachea?
Psudeostratified ciliated columnar epithelium scattered with goblet cells.
Where are the subepithelial seromucous gland most abundant in the trachea?
The posterior band of the trachea, that is devoid of cartilage.
Define chronic bronchitis
A cough productive of purulent sputum for at least 3 months of the year for at least 2 successive years.
What is the Small Airway Disease?
It is the thickening and fibrosis of the small airways.
The fibrosis separates it from emphysema.
What cell types make up an alveolus?
Type 1 and type 2 pneumocytes.
What does Fick's Law state?
The amount of gas that moves across a sheet of tissue is proportional to the area but inversely proportional to its thickness.
What is the mean pressure in the pulmonary artery?
What happens to the epithelium in the more peripheral branches of the bronchi/ bronchioles?
The ciliated epithelium changes from a columnar type to a more cuboidal type.
What is the water vapour pressure when added to inhaled air?
What are the sensors that control respiration?
- Medullary chemoreceptors in the brainstem
- Carotid and aortic body chemoreceptors; sense O2
- Hering-Breuer reflex in the lung - inhibits breathing
- Proprioceptive and other peripheral receptors.
Where are neuroendocrine cells most abundant?
In the smaller bronchi
How does the smooth muscle arrangement differ along the bronchial tree?
- In the main bronchi it is arranged in a similar fashion to the trachea, posteriorly, filling the gap of the incomplete cartilage rings.
- More distally, the arrangement becomes spiral, with the 2 layers running in opposite directions.
List the different severities of COPD, and what distinguishes them?
- Mild; FEV1 is 50-80% of predicted
- Moderate; FEV1 is 30-49% of predicted
- Severe; FEV1 is less than 30% of predicted
What are the 2 mechanisms causing a decrease in intrapleural pressure during inspiration?
- Lung expansion causing an increase in it's elastic recoil, thereby exerting greater force on the pleura.
- A pressure drop along the airways
What are the pores of Kohn?
Pores that allow communication between adjacent alveoli.
Which part of the bronchial tree is MALT found?
- At the bifurcations of the tubes
- The patches are larger at the more proximal bronchial bifurcations.
Which area of the lung is the best ventilated (volume of airflow) ?
The bases of each lung has a higher rate of ventilation
What is the pathological processes seen in chronic bronchitis?
- Hypertrophic galnds producing excessive mucous/ sputum
- Inflammatory cell infiltration.
What are the normal pressures of O2 and CO2 in the blood?
O2 - 11-13KPa
CO2 - 4.8-6KPa
What is the cross-sectional structure of a typical bronchus?
- Pseudostratified ciliated columnar epithelium
- Seromucous subepithelial glands
- Smooth muscle
- Elastic fibres
- Partial cartilaginous rings.
What are the causes of V/Q mismatch within the lung?
- Normal difference at the base of the lung; perfusion is greater than ventilation.
- Direct shunting of deoxygenated blood - bronchial circulation
- Anatomical dead space
- Bullae, or areas of underperfusion.
What is the normal ratio of FEV1:FVC?
What happens to the FEV1:FVC in obstructive and restrictive diseases of the lung?
Obstructive; Both FEV1 and FVC are reduced, but FEV1 is affected more, so ratio becomes less than 75%. Seen in COPD or asthma
Restrictive; Both are affected but to a similar extent, ratio is normal or higher than normal. Seen in lung fibrosis and interstitial pneumonias.
Where are goblet cells most abundant in the bronchial tree?
In the main and lobar bronchi
How long does each RBC spend in the capillary network of the lungs?
What is the function of type 2 pneumocytes?
- Surfactant production
- May act as stem cell precursors for type 1 pneumocytes
What is emphysema?
It is enlarged airspaces, distal to the terminal bronchioles, with destruction of alveolar walls.
What happens to the cartilage the further down the bronchial tree?
- It changes from partial rings to irregular cartilaginous plates
- Distally is it mainly located at bifurcations
What epithelial changes can occur in COPD lungs?
Metaplasia of the columnar epithelium to squamous epithelium.
What does Dalton's Law state?
The partial pressure of a gas in a mixture is the pressure that the gas would exert if it occupied the total volume in the absence of any other components
Px = (PB - 47) x Fx
What is the treatment for moderate COPD?
- Regular antimuscarinic; ipratropium or tiotropium or
- LAβ2A; salmeterol
- Add inhaled corticosteroids; beclometasome if FEV1 < 50% predicted or 2 exacerbations per year.
- Oral theophylline has a role
What is the difference between the course of the pulmonary arteries and veins?
- The pulmonary arteries follow the divisions of the bronchi towards the periphery.
- The pulmonary veins diverge and pass between the lobules of the lungs.
What pathology is caused by an increase in capillary pressure within the lung?
Pulmonary oedema; the increase in pressure can damage the thin walls, leading to plasma leakage into the alveolar space
What type of epithelium is found within the bronchioles?
Ciliated columnar epithelium, without psuedostratification
What epithelium types lines the terminal bronchioles?
Cuboidal ciliated epithelium
What does Henry's Law state?
The concentration of a gas dissolved in a liquid is proportional to its partial pressure.
Cx = K x Px
What is Boyle's Law?
P1V1 = P2V2
Explain the α1 anti-trypsin theory of emphysema?
- Lack of α1 anti trypsin allows uncontrolled action of neutrophil elastase and MMPs
This leads to alveolar wall destruction
- This also lead to a loss of elastic fibres within the lung, further exacerbating small airway collapse
What is the function of type 1 pneumocytes?
They provide a thin barrier for gaseous exchange.
What is bronchiectasis?
It is permanently dilated airways caused by chronic infections, usually from H. influenzae, Strep pneumoniae, Staph aureus and Pseudomonas aeruginosa.
Which gas most easily crosses the lung-air barrier?
CO2, it is about 20 x more rapidly diffused across the lung than oxygen
What are the functions of the trachealis muscle?
- Allow slight constriction of the trachea
- Prevents dilatation of the trachea
What is the function of the basal cells in the bronchi/bronchioles?
They act as a stem cell population.
What is the partial pressure of oxygen at sea level?
20.93/ 100 x 760 = 159mmHg or 21 kPa
What is Charles' Law?
V1T2 = V2T1