Anatomy and Physiology of the lungs Flashcards
What is the main function of the respiratory system
To bring air from the atmosphere and blood from the circulation into close proximity across the alveolar capillary membrane in order to facilitate the exchange of oxygen and carbon monoxide
Describe the structure of the trachea
Cartilaginous horseshoe shaped rings in the anterior and lateral walls and a flaccid posterior wall
What happens to the posterior wall of the trachea during coughing
It bulges forward
Where does the trachea divide into the right and left main bronchi
At the level of the sternal angle
What main bronchus is longer?
The left
If an inhaled foreign object was to get stuck, where is it most likely to get stuck
The right lung because the right main bronchus is more directly in line with the trachea
What do the main bronchi divide into?
Lobar bronchi
What do lobar bronchi divide into?
Segmental bronchi
What structure separates bronchi from bronchioles
The presence of cartilage in the bronchi
What are the bronchioles which are immediately proximal to the alveoli known as
Terminal bronchioles
Describe the epithelial lining of the bronchi
Ciliated and includes goblet cells
Describe what the mucociliary escalator is
The cilia beating in an organised fashion to move material trapped in the mucus layer upwards and out of the lung
Why is the mucociliary escalator so important?
It is an important part of the lung’s defences
What happens to the acinar mucu-secreting glands in the submucosa in chronic bronchitis
They show signs of hypertrophy
Name the two types of alveolar cells
Type 1 pneumocytes
Type 2 pneumocytes
What is the role of type 1 pneumocytes
They have flattened processes that extend to cover most of the internal surface of the alveoli
What is the role of type 2 pneumocytes
They contain lamellated structures that are concerned with the production of surfactant
Describe the blood supply to the lungs
Dual supply
1 from the pulmonary circulation and 1 from the systemic circulation
Where do the pulmonary venules drain?
Laterally to the periphery of lung lobules and then pass centrally in the interlobular and intersegmental septa and then they join to form the 4 pulmonary veins.
Where do some small bronchial arteries arise from?
The descending aorta
What might happen to the bronchial arteries in chronic pulmonary inflammation
They may undergo hypertrophy
Where does haemoptysis arise from in diseases such as bronchiectasis or aspergilloma
Bronchial arteries
What are the 2 steps of bringing oxygen into the body and removing carbon dioxide
1 - moving air in and out of the lungs (between outside world and alveoli)
2 - gas exchange (between airspace of alveoli and the blood)
Where is the function of the lungs coordinated
By a centre in the brain stem
What are the main 2 forces involved in breathing
Inherent elastic property of the lungs and the resistance to airflow thought the bronchi (airway resistance)
What is the principal muscle of inspiration
Diaphragm
Describe the location of the diaphragm
Domed position, high in the thorax
What happens to the ribs on inspiration
They move upwards and outwards
What happens to the abdominal cavity during inspiration
It is pushed inferiorly by the diaphragm
The inability to inflate the lungs is an example of what?
Restrictive ventilatory defect
What muscles elevate the upper ribs and sternum
The scalene muscles
What other muscles are involved in breathing
Sternocleidomastoids
Intercostal muscles
What are another group of muscles involved during coughing
Abdominal muscles
What counteracts the lungs tendency to contract
The semi-rigid chest wall
The opposing forces from the lung and the chest wall generate what type of pressure and where?
Negative pressure within the pleural space
What is the importance of the l=negative pressure
It maintains the lung in its stretched state
Define lung compliance
The change in lung volume brought about by a unit change in transpulmonary (intrapleural) pressure
What two things to the muscles of respiration have to overcome
1- the elastic properties of the lung and the chest wall
2 - the frictional forces opposing flow up and down the airways
Describe the relationship between the resistance to flow in a tube and the radius of the tube
Resistance is inversely proportional to the radius^4
Where is the greater part of total airway reisitance situated in a healthy individual
The large airways - layrnx, trachea, main bronchi
What type of pressure is generated in the alveolar space during expiration
A positive pressure
What happens to the maximum flow rate in COPD
It is reduced
What happens to the lung elastic recoil as the lung volume decreases
It diminishes and therefore provides less support for the airway
What is the maximum flow rate achievable dependent upon
The lung volume
What is FEV1?
The forced expiratory volume in 1 second
What must be in intimate contact for gas exchange to take place?
Air and blood
Where does the majority of air inhaled go to and why?
The bases of the lungs
They are essentially sitting on the diaphragm and are not as stretched as the upper parts of the lung
What is the driving pressure of the pulmonary circulation at rest?
15mmHg
What will happen to the PCO2 if the alveolar ventilation increases?
It will fall
What is PCO2 a sensitive index of ?
Alveolar ventilation
If alveolar ventilation were reduced, what would happen to the PO2?
It would also be reduced
What is the PO2 of moist atmospheric air?
20kPa
What is the dissociation curve?
the quantity of gas carried by blood when exposed to different partial pressures of the gas
Why does PO2 level off on the dissociation curve?
The haemoglobin is fully saturated
Describe the content of O2 and CO2 in areas of low V/Q
Rise in arterial CO2 and a fall in arterial O2
What allows us to distinguish a low oxygen level due to under ventilation from a level cause by intrinsic lung disease when looking at arterial blood gas results?
The alveolar gas equation
What happens in pure underventilation
An increase in PCO2 and a proportionate fall in PO2.
What does an increase in PCO2 and a proportionate fall in PO2 signify
Type 2 respiratory failure
A disturbance of VQ matching leads to a fall in what?
A fall in PO2 and no change in pCO2
What does a fall in PO2 and no change in pCO2 signify?
Type 1 respiratory failure
What is the principal driver of ventilation
CO2 (due to pH)
What is PCO2 maintained at in health
5.3kPa (40mmHg)
What happens if the PCO2 is increased above 5.3kPa
Hyperventilation
What happens if the PCO2 is decreased below 5.3kPa
Hypoventilation
What SpO2 is aimed for in patients with COPD
88-92%
When does hypoxia act as a stimulant
When the PO2 is less than about 8kPa