gas exchange in humans Flashcards
Features of gas exchange surfaces in humans?
- Large SA
- Thin surface (short diffusion pathway)
- Good blood supply (maintains steep conc gradient)
- Good ventilation with air (maintains steep conc gradient
- Moist (gases can dissolve & diffuse faster)
How are the lungs protected?
Air breathe in first goes where?
- By ribs
- Larynx then trachea
Where does gas exchange take place?
Alveoli; surrounded by capillaries, on the bronchioles
What happens during breathing in (inspiration)
- External intercostal muscles & diaphragm contract, diaphragm moves down as it contracts.
- Internal intercostal muscles relax.
- This causes the ribs to move upwards and outwards
- Volume of thorax increased.
- This decreases pressure inside thorax, drawing air in.
What happens during breathing out (expiration)
- Internal intercostal muscles contract.
- External intercostal muscles relax.
- This causes the ribs to move downwards and inwards
- Diaphragm relaxes; becomes dome shaped.
- Volume of thorax decreased.
- This increases pressure inside thorax, so air is forced out of the lungs out.
Explain the role of goblet cells, mucus and
ciliated cells in protecting the breathing system
from pathogens and particles
Goblet cells
* produce mucus to coat inner lining of trachea & bronchi
* mucus traps particles & pathogens
* found in the epithelium of respiratory passages & digestive system, which secrete mucus.
Ciliated cells
covered in hair like structures called cilia; waft mucus up to the back of the throat where it can be swallowed, pathogens to be killed by stomach acid.
* cilia beat to move mucus (rythmically in unison)
* mucus moved up & out of lung
Oxygen - percentage in inspired air, expired air
Inspired air - 21%
Expired air 16%
CO2 - percentage in inspired air, expired air
Inspired air - 0.04
Expired air 4
Water vapour - percentage in inspired air, expired air
inspired air - variable
expired air - usually v high (saturated)
