What is the blood-air barrier

The blood-qi barrier refers to certain hematopoietic problems in the alveolar function, which may even affect the normal blood flow in the human body. It is related to the individual's lung function, so it must be reasonably controlled in normal times to avoid the blood-qi barrier causing unnecessary trouble and burden to the body, so as not to aggravate some diseases.

Basic information: The blood-gas barrier refers to the structure through which gas exchange occurs between oxygen in the alveoli and carbon dioxide carried by blood in the alveolar capillaries.

It consists of six layers: a liquid layer containing pulmonary surfactant, an alveolar epithelial cell layer, an epithelial basement membrane, a gap between the alveolar epithelium and capillaries (stromal layer), a capillary basement membrane, and a capillary endothelial cell layer.

The alveoli are the last level (24 levels) of branches of the lung's parenchyma tissue and the place where gas exchange occurs during external respiration. There are about 300 million alveoli in an adult's lungs. Its size is approximately 0.2 mm. Many alveoli open into a common alveolar sac.

Alveoli are composed of:

Small alveolar cells, also known as type I alveolar cells, are about 0.1 microns thick, have a basement membrane at the base, and have no ability to proliferate. Large alveolar cells, also known as type II alveolar cells, secrete surfactant (dipalmitoylphosphatidylcholine) to reduce alveolar surface tension. Lung macrophages are derived from blood monocytes. Those that engulf more dust particles are called dust cells, while heart failure cells are macrophages that appear in the lungs of heart failure patients and engulf the decomposition products of hemoglobin. The alveoli are closely connected to the pulmonary capillaries. The membranes of the two are mostly fused, which facilitates the rapid diffusion of gases. The alveolar surface liquid layer, type I alveolar cells and basement membrane, thin layer of connective tissue, capillary basement membrane and endothelium constitute the so-called air-blood barrier.

Because the permeability of the capillary endothelium to fluid is higher than that of the alveolar cell endothelium, body fluid in patients with heart failure will leak into the connective tissue, causing interstitial emphysema.