11.3 - Ventilation
The breathing-system structures
- The lungs are the organs where air is taken in and let out.
- They sit inside the thorax - the chest cavity between the neck and the diaphragm.
- The lungs are protected by the ribcage, with intercostal muscles running between the ribs.
- Below the lungs, a sheet of muscle called the diaphragm separates the thorax from the lower part of the body.
- Thin pleural membranes surround the lungs themselves.
The path of air into the lungs
Air breathed in travels through a series of structures before reaching the sites of gas exchange:
- Nasal cavity - Air enters here first.
- Larynx - Air passes through next.
- Trachea (windpipe) - A hollow tube held open by C-shaped rings of cartilage, so it stays strong but can still move.
- Bronchi - The trachea divides into two of these tubes, one bronchus to each lung.
- Bronchioles - Each bronchus branches into progressively smaller tubes.
- Alveoli - The bronchioles end in these tiny air sacs, where gas exchange takes place.
TermDefinition
ThoraxThe chest cavity between the neck and the diaphragm.
DiaphragmA sheet of muscle below the lungs that separates the thorax from the lower part of the body.
TracheaThe tube, held open by rings of cartilage, that carries air from the mouth and nose to the lungs.
BronchiThe two tubes that the trachea divides into, leading to each lung.
AlveoliThe tiny air sacs in the lungs where gas exchange takes place.