Gas exchange in humans

• Rib cage: supports the lungs, moved by the intercostal muscles between them
• Lungs: a pair of lobes structures made up of bronchioles and alveoli
• Trachea: flexible airways supported by rings of cartilage, which prevents the trachea from collapsing when air pressure falls
• Bronchi: divides of the trachea, one into each lung. Produce mucus and trap dirt, and are ciliated to waft the mucus to the throat
• Bronchioles: subdivisions of the bronchi. Allows muscular walls to constrict, controlling the flow of air in and out of the alveoli
• Alveoli: small air sacs at the end of the bronchioles. Lined with epithelium, the elastic fibres allow the alveoli to stretch as they fill with air