Respiratory

Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified. Tiny hairs called cilia (pronounced: SIL-ee-uh) protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air.

The two openings of the airway (the nasal cavity and the mouth) meet at the pharynx (pronounced: FAR-inks), or throat, at the back of the nose and mouth. The pharynx is part of the digestive system as well as the respiratory system because it carries both food and air.

At the bottom of the pharynx, this pathway divides in two, one for food — the esophagus (pronounced: ih-SAH-fuh-gus), which leads to the stomach — and the other for air. The epiglottis (pronounced: eh-pih-GLAH-tus), a small flap of tissue, covers the air-only passage when we swallow, keeping food and liquid from going into the lungs.

The larynx, or voice box, is the top part of the air-only pipe. This short tube contains a pair of vocal cords, which vibrate to make sounds.