Regarding exchange of materials, gas exchange in the lung is one of the crutial topics in the I/GCSE Biology. In order to make sure a constant supply of oxygen for respiration, breathing in and out takes in oxygen as a supply for the cells and removes the waste carbon dioxide produced by the cells.
The lungs (found in the thorax) are protected by the rib cage. The lungs are separated from the digestive organs, found in the abdomen, by the diaphragm.
Diagram 1: The labelled diagram for human gas exchange system
When you breathe in…
- your ribs move UP and OUT
- your diaphragm flattens
- air is pulled INTO the lungs
When you breathe out…
- your ribs move DOWN and IN
- your diaphragm returns to its domed shape
- air is forced OUT OF the lungs
Diagram 2: the mechanism of inspiration and expiration
The lungs have been adapted especially for making gas exchange more efficient.
- made up of clusters of alveoli (tiny air sacs with large surface areas, and are kept moist)
- have a rich blood supply, which maintains a concentration gradient in both directions
- Carbon dioxide constantly being removed from the blood and oxygen constantly entering the lungs means that gas exchange happens at the highest concentration gradients to make it rapid and effective.
👇The diagram here shows an alveolus (singular of alveoli).👇
Adaptation of alveoli:
- spherical shape gives large surface area
- moist surface makes diffusion easy as gases can dissolve
- thin walls make diffusion easy
- good bloody supply
That's the end of the topic!
Drafted by Joey (Biology)