A transverse section of the thorax, showing the contents of the middle and the posterior mediastinum.
The thoracic wall (or chest wall) is the boundary of the thoracic cavity.
When not breathing for long and dangerous periods of time in cold water, a person's body undergoes great temporary changes to try and prevent death. It achieves this through the activation of the Mammalian diving reflex, which has 3 main properties. Other than Bradycardia and Peripheral vasoconstriction, there is a blood shift which occurs only during very deep dives that affects the thoracic cavity (a chamber of the body protected by the thoracic wall.) When this happens, organ and circulatory walls allow plasma/water to pass freely throughout the thoracic cavity, so its pressure stays constant and the organs aren't crushed. In this stage, the lungs' alveoli fill up with blood plasma, which is reabsorbed when the organism leaves the pressurized environment. This stage of the diving reflex has been observed in humans (such as world champion freediver Martin Štěpánek) during extremely deep (over 90 metres or 300 ft) free dives.
In rare cases intentional or accidental trauma may lead into chest wall (thoracic wall)necrosis. 
- Eskandarlou M, Moaddab AH. Chest wall necrosis and empyema resulting from attempting suicide by injection of petroleum into the pleural cavity. Emerg Med J. 2010 Aug;27(8):616-8. doi: 10.1136/emj.2009.073486. Epub 2010 Jun 17.
- Thoracic wall at the US National Library of Medicine Medical Subject Headings (MeSH)
- Anatomy photo:18:lo-0000 at the SUNY Downstate Medical Center
- chest+wall at eMedicine Dictionary