alveolocapillærbarren

The alveolocapillary barrier, also known as the respiratory membrane, is a critical structure in the lungs responsible for gas exchange between the air in the alveoli and the blood in the pulmonary capillaries. This thin barrier is composed of three primary layers: the alveolar epithelium, the capillary endothelium, and their fused basement membranes. The alveolar epithelium consists of type I pneumocytes, which are extremely thin cells that cover most of the alveolar surface and facilitate diffusion, and type II pneumocytes, which produce surfactant. The capillary endothelium is a single layer of cells forming the wall of the pulmonary capillaries, which are the smallest blood vessels in the lungs. The fused basement membranes lie between the alveolar and capillary cells, providing structural support and further reducing the diffusion distance.

The thinness and large surface area of the alveolocapillary barrier are crucial for efficient gas exchange. Oxygen from inhaled air diffuses across this barrier into the blood, while carbon dioxide from the blood diffuses into the alveoli to be exhaled. This process is driven by partial pressure gradients. Any thickening or damage to the alveolocapillary barrier, such as that seen in conditions like pulmonary edema or fibrosis, can impair gas exchange and lead to respiratory distress. The integrity of this barrier is essential for maintaining adequate oxygenation of the body and removal of carbon dioxide.