alveolærkapillærbarrieren

The alveolar-capillary barrier, also known as the respiratory membrane, is a crucial structure in the lungs responsible for gas exchange between the air in the alveoli and the blood in the pulmonary capillaries. This barrier is incredibly thin, typically only about 0.5 micrometers thick, to facilitate efficient diffusion of gases.

It consists of several layers. The innermost layer is the alveolar epithelium, which is primarily made up of type I pneumocytes, thin squamous cells. Outside this is the fused basement membrane of the alveolar epithelium and the capillary endothelium. The outermost layer is the capillary endothelium, composed of flattened endothelial cells lining the pulmonary capillaries.

The primary function of the alveolar-capillary barrier is to allow oxygen to diffuse from the inhaled air into the blood and carbon dioxide to diffuse from the blood into the alveoli to be exhaled. This process relies on the concentration gradients of these gases. The large surface area provided by the millions of alveoli and the dense network of capillaries further enhances the efficiency of gas exchange. Any damage or thickening of this barrier, such as in conditions like pneumonia or pulmonary fibrosis, can impair gas exchange and lead to respiratory distress.