alveoli- end in air sacs

bronchi- near the center of the chest.

bronchioles- divide into the smallest branches.

cellular respiration- when cells use oxygen and nutrients to produce energy, water, and carbon dioxide.

cilia- tiny, hairlike structures.

epiglottis- special leaflike piece of cartilage, closing the opening into the larynx during swallowing.

expiration- when the diaphragm and intercostal muscles relax.

external respiration- the exchange of oxygen and carbon dioxide between the lungs and the bloodstream.

inspiration- process of breathing in air.

larynx- voice box, lies between the pharynx and trachea.

internal respiration- exchange of carbon dioxide and oxygen between the tissue cells and the bloodstream.

lungs- division of the bronchi and alveoli.

nasal cavities- divides the nose into 2 hollow spaces.

nasal septum- wall of cartilage.

nose- has two openings through which air enters.

pharynx- or throat lies directly behind the nasal cavities.

pleura- each lung is enclosed in a membrane or sac.

respiration- process of inspiration and expiration.

respiratory system- consists of the lungs and air passages.

sinuses- cavities in the skull that surround the nasal area.

trachea- tube extending from the larynx to the center of the chest.

ventilation- process of breathing.