Flexi Says: Several types of cells form the tissues that make up the lungs. The lungs are covered by a thin tissue layer called the pleura. A large chunk of them are epithelial cells. These cells form the lining of the airways and also make mucus which acts as a lubricant and helps in protecting the lung tissues. In addition to these, other types of cells like nerve cells, blood cells, hormone-secreting cells and several types of connective tissue cells are also present in lungs.