Gas exchange and ventilation Flashcards
What happens to upper respiratory tract when inhalation
Tends to constrict when air is drawn into the lungs
What happens to lower respiratory tract when inhalation
expands when air is drawn into the lungs
Alveolar pressure
pressure inside the alveoli relative to atmospheric pressure
Intrapleural pressure
pressure between the pleural membranes
transmural pressure
Alveolar pressure MINUS intrapleural pressure
What happens in Inhalation
Intercostal muscles contract
Ribcage is raised
Diaphragm muscles contracts and flattens
volume of thoracic cavity increases
lungs are pulled open
air is pulled into lungs through trachea
What happens in exhalation
intercostal muscles contract
ribcage falls
diaphragm muscles relaxes and domed shape
volume of thoracic cavity decreases
lungs are compressed
expired gas flows out through trachea
What is Lung compliance
Measure of stretchiness of the lung
High lung compliance
very stretchy so a small amount of pressure results in a large increase in volume (easy to inflate)
Low lung compliance
Not very stretchy so a large amount of pressure required to increase in volume (difficult to inflate)
How does Surface tension and alveoli interact
watery lining on inner surface of alveoli Water molecules attract to each other in alveoli and gives a pull towards centre of alveolus causing alveoli difficult to inflate
Surfactant interact with alveoli
Some alveolar cells produce surfactant that surfactant sit on surface of watery lining so reduces ability for water molecules to attract each other reducing pull towards centre and meaning alveoli are easier to inflate
Tidal volume
Volume of air in a normal breath
residual volume
volume of air in lungs after maximum forceful expiration
Vital capacity
Maximum volume of air can be expelled from lungs after a maximum inhalation
Total lung capacity
The volume of air at maximum inflation
Typical total lung volume human 75kg
6L
Typical tidal volume human 75kg
0.5L
