Gas Exchange Flashcards
Why do mammals have an extremely high oxygen demand?
More aerobic respiration as they are very active and have to maintain a constant body temperature.
How is the trachea adapted?
Walls contain cartilage -> firm but flexible material so breathing can occur.
Walls lined with ciliated epithelia and goblet cells -> to trap dust/pathogens and take them with mucus to digestive system.
Structure of human lungs
2 x bronchi forming many branches of bronchioles, hundreds of millions of air sacs called alveoli.
Adaptations of alveoli
Many alveoli -> high surface area
One cell thick alveolar and capillary walls -> short diffusion distance
Extensive capillary network -> steep concentration gradient for oxygen
What does breathing do?
Brings fresh air from outside the body into the alveoli. Increases concentration gradients and therefore rate of diffusion.
What happens during inhalation?
The external intercostal muscles contract with the diaphragm meaning the pressure in lungs is less than atmospheric pressure and air moves into the alveoli.
What happens during exhalation?
The external intercostal muscles and diaphragm relax, reducing volume of thorax/lungs meaning air is pushed out the lungs as it is more than the atmospheric pressure.
Inhalation/exhalation passive/active?
Inhalation is active and exhalation is passive
When do the intercostal muscles contract?
When a person exhales strongly.
Where is oxygen provided to in insects?
Directly to cells
What are insects covered with?
A protective exoskeleton which gases cannot pass through.
How does gas pass through the exoskeleton of insects?
Spiracles on the surface
Is gas exchange in insects active or passive?
Passive
Where do the spiracles lead to?
Spiracles -> trachea -> network of tracheoles -> cells
Surface area to volume ratio in different organisms
Low in humans and fish but high in insects as they have a small size.
Concentration of oxygen in water
Much less than air
How does oxygen reach a fish’s blood?
Oxygenated water enters through mouth -> water passes over gills -> oxygen diffuses into blood (and carbon dioxide vice versa)
Structure of gills in fish
Contain gill filaments covered in numerous lamellae
How are lamellae adapted?
Massive surface area, short diffusion distance between walls and an extensive network of capillaries.
How are fish adapted to have a counter current system?
Blood and water move in opposite directions, maintaining a steep concentration gradient for oxygen.
