alveoli:Little "sacs" at the end of the bronchioles where most of the gas exchange occurs.
asthma:A chronic illness in which the bronchioles are inflamed and become narrow.
bronchitis:An inflammation of the bronchi.
diaphragm:A sheet of muscle that extends across the bottom of the rib cage. When the diaphragm contracts the chest volume gets larger and the lungs take in air; when the diaphragm relaxes, the chest volume gets smaller and air is pushed out of the lungs.
emphysema: A chronic lung disease caused by loss of elasticity of the lung tissue.
epiglottis:A flap of connective tissue that closes over the trachea when food is swallowed to prevent choking or inhaling food.
exhalation:Pushing air out of the body through the nose or mouth.
external respiration:The movement of oxygen into the body and carbon dioxide out of the body.
inhalation:Taking air into the body through the nose and mouth.
internal respiration:The exchange of gases between the blood and the cells of the body.
larynx:Found just below the point at which the pharynx splits into the trachea and the esophagus. Your voice comes from your larynx; air from the lungs passes across thin membranes in the larynx and produces sound; also called the voicebox.
lung cancer:A disease where the cells that line the lungs grow out of control; the growing mass of cells pushes into nearby tissues and can affect how these tissues work.
pathogen: An organism that causes disease in another organism; certain bacteria, viruses, and fungi are pathogens of the respiratory system.
pharynx:A long tube that is shared with the digestive system; both food and air pass through the pharynx.
pneumonia:An illness in which the alveoli become inflamed and flooded with fluid.
trachea:A long tube that leads down to the chest where it divides into the right and left bronchi in the lungs; also called the windpipe.
tuberculosis (TB): A common and often deadly infectious disease caused by a type of bacterium called mycobacterium.