Respiratory Physiology 2 Flashcards
Define TIDAL VOLUME
The volume of air you breathe in and the volume of air you breathe out at rest (~ half capacity)
Define INSPIRATORY RESERVE VOLUME
The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration.
Define EXPIRATOY RESERVE VOLUME
The maximum volume of air which can be expelled from the lungs at the end of a normal expiration.
Define VITAL CAPACITY
Maximum amount of air that can be expired after a maximum inspiration
Define RESIDUAL VOLUME
The volume of gas in the lungs at the end of a maximal expiration
What is covered by PLEURAL MEMBRANES?
The lungs and interior of the thorax
VISCERAL PLEURAL MEMBRANE
Lines the outer surface of the lungs
PARIETAL PLEURAL MEMBRANE
Lines inner surface of the ribs
How are lungs stuck to the rib cage?
Through the relationship of the pleural membranes
How is recoil of the chest wall in normal expiration brought about?
Recoil of the elastic connective tissue in the lung
What is the relationship between Boyle’s law and the mechanics of breathing?
Increased volume = decreased pressure
Decreased volume = increased pressure
How does INSPIRATION happen?
Use of external intercostals muscles and the diaphragm
EXPIRATION is passive at rest, however during severe respiratory load what does it use?
uses internal intercostal and abdominal muscles
What is INTRA-THORACIC (Alveolar) PRESSURE (PA)
Pressure inside the thoracic cavity, (essentially pressure inside the lungs).
May be negative or positive compared to atmospheric pressure
What is INTRA-PLEURAL PRESSURE (Pip)
Pressure inside the pleural cavity, typically negative compared to atmospheric pressure
What is TRANSPULMONARY PRESSURE (PT)
Difference between alveolar pressure and intra-pleural pressure.
Almost always positive because Pip is negative
What are the 2 cell types that make up the alveolar wall?
- Thin walled “Type I” cells which permit gas exchange
- Specialised “Type II” cells which secrete surfactant fluid
What is the purpose of SURFACTANT?
Reduces surface tension on alveolar surface membrane
When does surface tension occur?
where ever there is an air-water interface and refers to the attraction between water molecules
When is SURFACTANT more effective?
In small alveoli than large alveoli because surfactant molecules come closer together and are therefore more concentrated.
What does SURFACTANT prevent?
Alveolar collapse
Define COMPLIANCE
Change in volume relative to change in pressure
It represents the stretchability of the lungs (not the elasticity!)
HIGH COMPLIANCE =
large increase in lung volume for small decrease in ip pressure
LOW COMPLIANCE =
small increase in lung volume for large decrease in ip pressure
What is between the surfaces of the pleural membranes
An extremely thin layer of intrapleural fluid.
