Final answer:
A spontaneous pneumothorax occurs when a lung bleb ruptures and air accumulates in the pleural space, causing pressure and a potential lung collapse. This condition interrupts the normal pressure balance in the thoracic cavity which is maintained by the pleural fluid between the visceral pleura and the parietal pleura.
Step-by-step explanation:
The condition described is known as a spontaneous pneumothorax, sometimes referred to as a collapsed lung. It occurs when a lung bleb, which is essentially a small blister on the lung surface, ruptures and breaks through the visceral pleura, the layer of tissue that covers the lung. As a result, there's an open communication between the trachea and the thorax outside of the lungs, leading to an accumulation of air in the pleural space (the space between the visceral and parietal pleura). This collection of air can cause a lung to collapse, creating significant pressure within the thorax, which is a critical condition that can reduce lung volume and impede normal breathing.
The pleurae consist of two layers: the visceral pleura, which is immediately superficial to the lungs, and the parietal pleura, which lines the thoracic cavity. The space between them, known as the pleural cavity, normally contains a small amount of pleural fluid that lubricates the surfaces, reducing friction and facilitating smooth breathing movements. If the balance of pressures within the pleural cavity is disturbed, as in the case of a pneumothorax, the negative intrapleural pressure is lost, leading to a collapse of the affected lung.