In a pulmonary fibrosis, the connective tissue portion of the lung grows abnormally. It is integrated into the superordinate group of so-called interstitial pulmonary diseases. Many different diseases can cause pulmonary fibrosis. The causes can be completely different, but the consequences for the lung are the same. The respiratory organ consists of the air-conducting parts and the connective tissue matrix.
The air-conducting parts consist of the bronchial tubes, which continue to branch of into smaller bronchioles and finally lead into the smallest functional units of the lung, the pulmonary air sacs (alveoli). The pulmonary air sacs are surrounded by a fine network of blood vessels. The gas exchange takes place via a thin skin called the alveolar membrane. This means that the inhaled oxygen enters the bloodstream here. Conversely, the used carbon dioxide is released from the blood into the lungs and exhaled.
The connective tissue between the air-conducting structures gives stability to the lung and is therefore essential. This "scaffolding" is called interstitium in medical terminology. For this reason, physicians speak of interstitial pulmonary diseases in the case of corresponding disorders in this area. Inflammation in particular leads to proliferation of this connective tissue. This also thickens the wall between the pulmonary alveoli and the blood vessel, meaning the gas exchange becomes less effective. There is often no cause for this disease.