Alveolevæggene

Alveolevæggene, often translated as alveolar walls, are the thin structures that form the tiny air sacs, called alveoli, in the lungs. These walls are primarily composed of a single layer of flattened cells, known as type I pneumocytes, and a basement membrane. This extremely thin structure is crucial for efficient gas exchange. Oxygen from the inhaled air can easily diffuse across the alveolar wall into the bloodstream, while carbon dioxide from the blood diffuses in the opposite direction to be exhaled.

Scattered within the alveolar walls are also type II pneumocytes. These cells are cuboidal and play a vital role in producing and secreting pulmonary surfactant. Surfactant is a substance that reduces the surface tension of the fluid lining the alveoli, preventing them from collapsing during exhalation and making breathing easier. The alveolar walls also contain a rich network of capillaries, the smallest blood vessels, which are in very close proximity to the alveoli. This close anatomical relationship facilitates the rapid transfer of gases between the air in the lungs and the blood. The entire structure is supported by a delicate network of elastic fibers, which allows the alveoli to expand and recoil with each breath.