Human beings have a pair of lungs, each surrounded by a twin-layered membrane called the pleura, which is made up of epithelial cells. The membrane is quite important since it secretes fluids that help in lubrication of various internal body parts in order to prevent friction that may be caused as a result of constant muscle movement.
The pleura membrane ensures that lungs can carry out their functions without much difficulty as it protects and lubricates them. The pleura is divided into two layers: the inner part called the visceral, and the outer part is called the parietal pleura. Human beings use their lungs to process inhaled oxygen and to get rid of carbon dioxide. The left lung is normally smaller in size since it is located very close to the heart.
The lungs make up an important part of the human respiratory system, which consists of the nose, wind pipe and other body parts that facilitate breathing. In order to enjoy a healthy respiratory system, human beings should always ensure they breathe in fresh air and avoid toxic substances, such as smoke or dangerous gases. When dealing with chemicals, human beings should wear masks to prevent toxins from reaching the lungs.