Final answer:
A pneumothorax is a collapsed lung due to air entering the pleural cavity. Tension pneumothorax is more severe, causing pressure build-up. Hemothorax is the presence of blood in the pleural cavity.
Step-by-step explanation:
A pneumothorax is a condition where air enters the pleural cavity, causing the lung to collapse. This can happen spontaneously or as a result of trauma. Tension pneumothorax is a more severe form of pneumothorax where air continues to accumulate in the pleural cavity, causing pressure to build up and compressing the lung and other structures in the chest like the heart. Hemothorax, on the other hand, is the presence of blood in the pleural cavity, usually as a result of injury or bleeding from the lung or chest wall.