Final answer:
A puncture to the pleural space allowing air between the visceral and parietal pleura is called a pneumothorax. This condition occurs when air enters the pleural cavity, potentially leading to a collapsed lung. Pneumothorax can be spontaneous or result from trauma such as a puncture wound.
Step-by-step explanation:
A puncture to the pleural space by a knife, a gun, or a broken rib that allows air between the parietal and visceral pleura is called a pneumothorax. This condition occurs when air enters the pleural cavity, the space between the visceral pleura (innermost layer of the pleura that is superficial to the lungs and extends into the lung fissures) and the parietal pleura (which lines the interior of the thorax). Pneumothorax can disrupt the delicate balance of intrapleural pressure needed for proper lung function, as normally this pressure is negative relative to atmospheric pressure, aiding in lung expansion. If air accumulates in the pleural space, it can cause the lung to collapse, leading to reduced lung volume and respiratory distress. The presence of air where it shouldn't be can be categorized as either spontaneous pneumothorax, which means it occurred without an apparent cause or due to lung disease, or as a traumatic pneumothorax caused by an external injury such as a puncture wound.