3.1.2 Mammalian gaseous exchange system Flashcards
What does the gaseous exchange system in mammals consist of?
Lungs and associated airways that carry air into and out of lungs.
How can air pass to the lungs?
Through the nose, into the trachea, bronchi and bronchioles until it reaches the alveoli.
Where does the exchange of gases take place in the lungs
In the alveoli.
What protects the lungs?
The ribcage.
What holds the ribs together?
Intercostal muscles.
What do both the intercostal muscles and the ribcage help to do?
Help to produce movement of breathing (ventilation)
Explain the process of how gaseous exchange in the lungs occur. (4)
-Gases pass via diffusion through thin walls in alveoli.
-O2 passes from air in alveoli to the blood in the capillaries
-CO2 passes from blood to the air in the alveoli.
-Lungs must maintain steep co2 gradient to ensure diffusion can continue
How does large surface area of the lungs help gaseous exchange
-Individual alveoli are small
-Combined the total surface area of lungs is larger than of our skin.
-Total surface area of exchange surface in humans is about 70m(2)
-Large surface area provides more space for molecules to pass through.
Why must the lungs produce a surfactant?
Alveoli coated in moisture that evaporates as we breathe in/out
-Lungs must produce a surfactant that coats the internal surface of the alveoli to reduce the cohesive forces between water molecules
-These forces tend to make alveoli collapse
How does the permeability of the exchange barrier help gaseous exchange?
-The barrier is compromised of the call of alveolus and wall of blood capillary
-It is permeable to co2 and o2 as the molecules are small and non-polar
-Allows molecules to pass through efficiently
What are some adaptations to reduce the distance the gases have to diffuse?
-Alveolus wall is one cell thick
-Capillary wall is one cell thick
-Both walls are made of squamous cells (thin/flattened)
-Capillaries in close contact with alveolus walls
-Capillaries are narrow, red blood cells are closer to air in alveoli causing rate of flow to decrease.
How does a good blood supply help gaseous exchange?
-Maintains a steep concentration gradient so that gasses continue to diffuse.
How does ventilation help gaseous exchange?
Replaces the used air with fresh air, bringing in more o2 and removing co2, ensures that:
-Conc of o2 in air of alveolus remains higher than that in the blood
-Conc of co2 in alveoli remains lower than that in the blood
This. maintains concentration gradient for diffusion.
Explain the process of inspiration and the relevant actions of muscles involved.
-Diaphragm contracts to move down and become flatter
-External intercostal muscles contract to raise the ribs
-The volume of the chest cavity is increased
-Pressure in chest cavity drops below the atmospheric pressure
-Air is moved into the lungs
Explain the process of expiration and the relevant actions of muscles involved.
-Diaphragm relaxes and is pushed up by the displaced organs underneath
-External muscles relax and ribs fall, internal intercostal muscles can contract to push air out more forcefully
-Volume of chest cavity decreases
-Pressure increases
-Air moved out of lungs
