Exchange of gases in the lungs Flashcards
Where does gas exchange take place in mammals?
Gas exchange occurs at the epithelium of the alveoli in the lungs
What three properties make exchange surfaces efficient?
1/ Thin - allowing short diffusion pathway
2/ Partially permeable - allowing selective movement of gases
3/ A large surface area - increasing the rate of diffusion
Why must a diffusion gradient be maintained at the alveolar surface?
To ensure a constant supply of oxygen to the body for respiration
What are alveoli?
Alveoli are minute sacs, located in the lungs
What two factors help maintain a diffusion gradient in the lungs?
The movement of the environmental medium (air) through ventilation and the movement of the internal medium (blood) through circulation
Why are specialised exchange surfaces often located inside an organism?
Because they are thin and easily damaged, so they need protection
Why do mammals need a ventilation system for their lungs?
Diffusion alone is too slow to maintain adequate oxygen and carbon dioxide transfer
What is the role of ventilation in the lungs?
Ventilation moves the external medium (air) over the exchange surface, maintaining a diffusion gradient
What type of transport is breathing?
Mass transport, which helps move large volumes of gases efficiently
Why are pulmonary capillaries so narrow?
How thick are the walls of pulmonary capillaries?
To ensure red blood cells are flattened against the capillary walls, reducing the diffusion distance for gases
Pulmonary capillaries are a single layer of cells thick
Why is the diffusion of gases between the alveoli and the blood very rapid?
Several adaptations enhance diffusion speed, including slow movement of red blood cells, thin exchange surfaces, large surface areas, and constant ventilation
How does the movement of red blood cells through pulmonary capillaries aid diffusion?
Red blood cells slow down, allowing more time for diffusion to occur
How does the positioning of red blood cells help diffusion?
Red blood cells are flattened against the capillary walls, reducing the diffusion distance for gases
Why does the thinness of alveolar and capillary walls increase diffusion efficiency?
Both walls are very thin, so the diffusion distance is very short
How does the surface area of alveoli and pulmonary capillaries affect diffusion?
A very large total surface area provides more space for gas exchange
How do breathing movements and blood circulation maintain a steep concentration gradient?
Ventilation of the lungs and circulation of blood continuously refresh oxygen and carbon dioxide levels, keeping diffusion efficient
What role does blood flow in the pulmonary capillaries play in diffusion?
It maintains a concentration gradient, ensuring continuous gas exchange
