Heart and lung anatomy. Artwork of a posterior (from behind) view of the heart and lungs. The heart (mostly obscured) is a hollow muscle that pumps blood around the body and to the lungs. One lung is shown here (left) with the other one shown only as bronchioles (airways, red). Heart and lung blood vessels (pink) are also shown. Air passes into and out of the lungs through the trachea (upper centre), with the pharynx and nasal passages at top. In the lungs, the process of gas exchange with the blood adds oxygen and removes carbon dioxide.