3.3.2 Gas Exchange Flashcards
Describe changes to the diaphragm upon inspiration. (2)
- Diaphragm contracts
- And flattens
Explain how the diaphragm causes air to move into the lungs. (3)
- Diaphragm contracts and flattens
- Increases the volume of the thorax
- Air moves down a pressure gradient and into the lungs
Describe how oxygen in the alveoli enters the blood capillaries. (2)
- Oxygen DIFFUSES through the epithelium of the alveoli
- and through the endothelium of the blood capillaries
Miner’s lung is a disease caused by breathing in dust in coal mines. The dust causes the alveolar epithelium to become thicker. People with miner’s lung have lower concentration of oxygen in their blood than healthy people.
Describe the path by which oxygen goes from an aveolus to the blood. (2)
- By diffusion
- Through the epithelium of the alevolus and through the endothelium of blood capillaries
Explain why people with miner’s lung have a lower concentration of oxygen in their blood. (1)
Thicker alveolar wall so longer diffusion pathway
In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries.
Describe how ventilation helps to maintain this difference in concentration. (2)
- Air with a higher oxygen concentration DRAWN INTO lungs upon inspiration
- Air with a lower oxygen concentration REMOVED from lungs upon expiration.
Give one other way that helps to maintain the difference in oxygen concentration. (1)
Circulation OF BLOOD
The diaphragm helps to bring abou the increase in the total volume of air breathed out. Explain how. (3)
- Diaphragm relaxes
- Diaphragm domes
- Volume of the thorax decreases
Curve A could be used to find the total volume of air that this person could breathe out in one complete breath. Describe how. (2)
- Extrapolate/ extend the curve
- Read off where curve flattens
Destruction of pahgocytes causes the lungs ti be more suspectible to infections. Explain why. (2)
- Phagocytes engulf and destroy pathogens
- Lung infections are caused by inhaling phagocytes/fibres
The reduced elasticity of the lungs causes breathing difficulty. Explain how. (2)
- MORE residual air in the lungs as they don’t deflate as much upon expiration
- Reduces OXYGEN concentration between the lungs and the environment
- Reduces rate of OXYGEN diffusion into the blood
Apart from reduced elasticity, explain how changes to the lung tissue reduce the effiency of gas exchange. (4)
- Alevolar walls thicken
- Longer diffusion pathway for gas exchange
- Scarred tissue
- Decreases surface area for gas exchange
Explain an advantage of a counter-current mechanism. (2)
- Diffusion gradient maintained across the gills
- At every point of contact oxygen concentration in water is higher than the oxygen concentration in the blood
- (or) more oxygen diffuses into the blood
Gas exchange in fish takes place in gills. Explain how two features of gills allow efficent gas exchange. (2)
- thin EPITHELIUM so short diffusion pathway
- Many gill filaments and lamellae so large surface area for diffusion
- Counter-current mechanism to maintain diffusion gradient
Describe the relationship between body mass and oxygen uptake. (1)
- The higher the body mass, the lower the oxygen uptake per gram of body mass
- Negative corelation
