You have a cold and keep coughing up loose phlegm. This is your respiratory system in action. The system acts as a first line of defense against body invaders-as in the case of harmful gases such as ammonia, and irritants such as pollen. It is also the mechanism by which oxygen is supplied to the body and carbon dioxide is exhaled. When this oxygen supply is cut off, death may result in a matter of minutes.
Mucus contains antibodies and other chemical substances able to kill viruses and bacteria.
The pharynx connects the mouth and nasal passages with the larynx, a muscle and cartilage substance in which the voice box is located. The trachea, commonly referred to as the windpipe, is the long passageway that transports air to the lungs. The bronchi are branches of the trachea that extend into the lungs. Together with the trachea, the structure resembles an upside-down tree. The diaphragm is a wall of muscle and connective tissue separating the thoracic cavity from the abdominal cavity.