It penetrates the mucosa.

You know, this is pair of lungs and the bronchial tree.

It is also extremely dry at cruising altitude, and this causes sore eyes, dry skin and mucosa on long flights.

The gastric mucosa protects itself from gastric acid with a layer of mucus, the secretion of which is stimulated by certain prostaglandins.

It enters our body through the nose and mouth, moves down into the pharynx, trachea and bronchial tubes, and ultimately reaches the alveoli air sacs in the lungs.