- Spiracles are openings. Trachea are tubes.
- Gas
- Moves randomly (brownian motion).
- Can dissolve in liquids.
- Diffuse down their concentration gradient.
- Move faster in air than in liquids.
- Most gasses don't have a charge and can easily diffuse across hydrophobic membranes.
- Maximizing Gas Exchange
- Increase surface area (branching pathways).
- Minimize distance for diffusion (thin tissues).
- More airflow
- More blood flow
CO2 comes from the Kreb's cycle. O2 is needed to bind free electrons from ETC.
- Fish Gills
- Have folds for increases surface area.
- Oxygen diffuses out of the water and into the blood.
- Countercurrent flow of blood and water maximizes oxygen diffusion.
- Bird Circulation
- Unidirectional Flow
- Continuous gas exchange
- Air sacs act as bellows.
- Gas exchange in parabronchi between air sacs.
- Air capillaries allow for crosscurrent gas exchange.
Trachea > Bronchi > Branchioles > Aveol
- Aveoli
- Small, thin walled air sacs for gas exchange.
- Enveloped by capillaries with lots of surface area.
Since circulatory system is closed, gas diffusion across two very thin membranes (blood vessel and aceoli).
- Mucus secretions in lung tissue
- Prevents water loss
- Traps pathogens
- Remove particulate matter.
- Cilia movement, beat in unison to expel mucus + particles.
- Amphibian Lungs
- Precursors to terrestrial reptiles/mammals.
- Have outcroppings to increase surface area.
- Folding/branching increases as evolution develops.
- Surfactants
- Lungs have lipids and proteins to reduce surface tension and adhesion, avoids sticking and collapse.
- Tidal Ventilation
- Airflow not unidirectional, not continuous.
- Same path for inhaling as for exhaling.
- Not countercurrent.