Lungs Non respiratory roles 

In addition to their role in respiration, the lungs also -

• Alter the pH of blood by facilitating alterations in the partial pressure of carbon dioxide
• Filter out small blood clots formed in veins
• Filter out gas micro-bubbles occurring in the venous blood stream such as those created after scuba diving during decompression.
• Influence the concentration of some biologic substances & drugs used in medicine in blood
• Convert angiotensin I to angiotensin II by the action of angiotensin-converting enzyme
• May serve as a layer of soft, shock-absorbent protection for the heart, which the lungs flank & nearly enclose.
• Immunoglobulin-A is secreted in the bronchial secretion & protects against respiratory infections.
• Maintain sterility by producing mucus containing antimicrobial compounds. Mucus contains glycoproteins, e.g. mucins, lactoferrin, lysozyme, lactoperoxidase. We find also on the epithelium Dual oxidase 2 proteins generating hydrogen peroxide, useful for hypothiocyanite endogenous antimicrobial synthesis. role not in place in cystic fibrosis patient lungs.
• Ciliary escalator action is an important defence body system against air-borne infection.The dust particles & bacteria in the inhaled air are caught in the mucous layer present at the mucosal surface of respiratory passages & are moved up towards pharynx by the rhythmic upward beating action of the cilia.