6.4 Gas exchange

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Distinguish between ventilation, gas exchange and cell respiration.
- Ventilation: process of bringing fresh air to the alveoli and removing stale air
- Gas exchange: process of swapping one gas for another
- Cell Respiration: release of energy in the form of ATP in the cytoplasm and the mitochondrion
Explain the need for a ventilation system.

To maintain concentration gradients in the alveoli.
Describe the features of alveoli that adapt them to gas exchange.
- Large surface area due to the combined spherical shape (600 million alveoli = 80 m2)
- Flattened epithelial cells of alveoli and close association with capillaries
- Short diffusion distance from alveoli to blood (0.5-1.0 um)
- Dense capillary network
- Moist surface for the solution of gases
Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli.
- (a) Trachea
- (b) Cartilage ring support
- (c) Bronchi (plural)
- (d) Lung
- (e) Heart
- (f) Sternum
- (g) Rib cage
- (h) Bronchioles
- (j) Alveoli
- (k) Diaphragm
Explain the mechanism of inspiration in the lungs.

The diaphragm contracts and flattens downwards. The external intercostal muscles contract, pulling the ribs up and out this increases the volume of the thorax this increases the lung and alveoli volume this decreases the pressure of air in the alveoli below atmospheric (Boyle's law) air flows in to equalise the pressure.