alveolevæggenes

Alveolevæggene, or alveolar walls, are the extremely thin structures that enclose the alveoli within the lungs. These walls are the primary sites of gas exchange in the respiratory system. Each alveolar wall is composed of several layers, including a single layer of squamous epithelial cells called type I pneumocytes, a basement membrane, and a thin layer of endothelial cells that form the wall of the adjacent capillary. This close proximity and minimal thickness facilitate the diffusion of oxygen from the inhaled air into the bloodstream and carbon dioxide from the blood into the alveoli for exhalation.

Scattered among the type I pneumocytes are type II pneumocytes. These cells are more cuboidal in shape and are responsible for producing and secreting pulmonary surfactant. Surfactant is a complex mixture of lipids and proteins that reduces the surface tension of the fluid lining the alveoli. Without surfactant, the alveoli would collapse due to the high surface tension, making breathing impossible. The alveolar walls also contain a sparse population of alveolar macrophages, which are immune cells that help to clear inhaled particles and pathogens from the alveolar space. The intricate structure of the alveolevæggene, with their vast surface area and thinness, is crucial for efficient respiration.