Type I alveolar cells, also known as type I pneumocytes, are thin, flat cells that line the alveoli in the lungs. They cover about 95% of the alveolar surface area and play a crucial role in gas exchange. Their thin structure allows for efficient diffusion of oxygen and carbon dioxide between the air in the alveoli and the blood in the surrounding capillaries. These cells are part of the respiratory system and are essential for maintaining proper lung function. Type I alveolar cells are supported by type II alveolar cells, which produce surfactant to reduce surface tension and prevent alveolar collapse. Together, they ensure effective respiration and overall lung health.