These are the nose, pharynx or throat (the large cavity behind the nose and mouth), larynx, trachea or windpipe, and bronchi or bronchial tubes. The larynx lies in front of the lower part of the pharynx and is the organ where the voice is produced (see VOICE AND SPEECH) by aid of the vocal cords. The opening between the cords is called the glottis, and shortly after passing this the air reaches the trachea or windpipe.

The windpipe leads into the chest and divides above the heart into two bronchi, one of which goes to each lung, in which it splits into finer and finer tubes – bronchi and bronchioles (see LUNGS). The larynx is enclosed in two strong cartilages: the thyroid (of which the most projecting part, the Adam's apple, is a prominent point on the front of the neck), and the cricoid (which can be felt as a hard ring about an inch below the thyroid). Beneath this, the trachea – which is stiffened by rings of cartilage so that it is never closed, no matter what position the body is in – can be traced down until it disappears behind the breastbone.