What membrane is closest to the lungs?

The visceral pleura is the correct answer because it is the membrane that directly covers the lungs. This serous membrane forms a protective layer around each lung, providing a smooth surface that allows for frictionless movement during breathing. The visceral pleura is tightly adhered to the lung tissue, which is crucial for lung expansion and contraction as air is inhaled and exhaled.

In contrast, the parietal pleura is the layer that lines the thoracic cavity, providing a separation between the lungs and the chest wall. Although both pleurae are part of the pleural sac, the visceral pleura is the one that is intimately associated with the lungs themselves.

The pericardium, while also a serous membrane, encases the heart and is not related to the lungs. The endothoracic fascia is a connective tissue layer that lies beneath the parietal pleura and is also not directly associated with the lungs. Thus, the visceral pleura is distinctly the closest membrane to the lungs, making it the correct choice in this context.