Mammalian gas exchange and ventilation Flashcards
Why is it not possible to expel all air from the lungs?
- thorax cannot be completely flattened
- trachea/bronchi held open by cartilage
Why are specialised exchange surfaces are needed by some organisms?
- they have a low SA:V so exchange surfaces increase that
- maximise efficiency of diffusion
- ensure the demand for oxygen and glucose is met
What are the 4 features of efficient exchange surfaces?
- Increased surface area
- Thin layers
- Good blood supply
- Ventilation to maintain a diffusion gradient
Why does an increased surface area make an exchange surface efficient?
Provides the area needed for exchange overcomes limitations of low SA:V ratio
Why do thin layers make an exchange surface efficient?
the distances that substances have to diffuse across is short making it fast and efficient
Why does a good supply make an exchange surface efficient?
the greater the difference in concentration the greater the rate of diffusion. A good supply means substances are constantly being delivered and removed, maintaining the steep concentration gradient
Why does ventilation make an exchange surface efficient?
For gases ventilation helps to maintain concentration gradients
How is the nasal cavity adapted for the gas exchange system?
- good blood supply warms air to body temperature
- cells secrete muscus to trap dust and bacteria to protect lung tissue
- moist surfaces reduce evaporation from the exchange surfaces which increase humidity
How is the trachea adapted for the gas exchange system?
- supported by incomplete rings of strong, flexible cartilage to allow for movement and prevent the trachea from collapsing
- lined with ciliated epithelium and goblet cells
What is the function of goblet cells?
Secrete mucus which traps dust and microogranisms
What is the function of ciliated epithelial cells?
Cilia beat and move mucus away from the lungs, protecting them
How are the bronchi adapted for the gas exchange system?
-supported by small rings of cartilage
How are bronchioles adapted for the gas exchange system?
- contain no cartilage
- contain smooth muscle
- smooth muscle contracts when bronchioles constrict and relaxes when they dilate
How are the alveoli adapted for the gas exchange system?
- very thin walls
- contain elastic fibres which allow alveoli to stretch as air is drawn n and when they return to size help squeeze air out
- good capillary blood supply
- coated in surfactant
What is breathing?
The movement of air in and out of the lungs