Lungs
The lungs
The lung is the essential organ of respiration in air-breathing vertebrates. Its principal function is to transport oxygen from the atmosphere into the bloodstream, and to excrete carbon dioxide from the bloodstream into the atmosphere. It accomplishes this task through a variety of specialized cells that form millions of tiny, exceptionally thin-walled air sacs where gas exchange takes place.
Function of the Lungs
Air, which is inhaled through the mouth and nasal passages, travels through the windpipe or 'trachea' into two main air passages. These divide into smaller branches which separate into even smaller "twigs" like an upside-down tree. The respiratory system is mainly contained in two lungs. Through the thin walls of these lungs, gasses pass into and out of the blood.
The right lung is made up of three compartments, each of which contain a branch and each of which stems off into smaller 'twigs', which hold the air sacs that process the oxygen in the air to be released into the blood and to remove carbon dioxide, which is exhaled through the nose and mouth.
The left lung cavity contains only two sections and encloses the heart, which processes the oxygenated blood and returns deoxygenated blood into the lungs for exhalation.
Breathing is an automatic process which comes from the brain stem and is so strong a force that the involuntary reflexes will not allow us to stop breathing for any length of time. The passageways in the respiratory system are lined with various types of epithelia to prepare the air properly for utilization and with hair-like fibers called cilia that move in a wave-like motion to sweep debris out of the lungs for removal.