Ace the 2026 Basic and Clinical Sciences Challenge – Test Your Brain and Boost Your Brilliance!

Pneumocyte type I cells are flattened, thin, squamous epithelial cells that line the alveoli in the lungs. Their primary function is to facilitate gas exchange between the air in the alveoli and the blood in the surrounding capillaries. Because of their thin structure, they provide a minimal barrier to diffusion, which is essential for efficient oxygen and carbon dioxide transfer.

In contrast, other cell types listed do not possess the same characteristics. For instance, cuboidal cells, which are typically found in glands and certain epithelial layers, have a distinct cubic shape and are not as specialized for gas exchange. Columnar cells have a taller, column-like appearance and are commonly found lining organs in the gastrointestinal tract, contributing to absorption and secretion processes but not gas exchange in the lungs. Non-ciliated cells, while applicable to some respiratory epithelium, do not specifically describe the structural properties of pneumocyte type I cells.

Thus, identifying pneumocyte type I as squamous cells underscores their significant role in respiratory physiology, emphasizing their adaptation for gas exchange due to their thin, flat morphology.