Respiratory system

• Nostrils: the two openings in the nose, mostly made up of cartilage, which makes the nose flexible and strong.
• Nasal cavity: tiny blood vessels in the nasal cavity warm the incoming air.
• Pharynx (throat): part of the mouth arch into a tube. It is connected to both the nose and mouth, and acts as passageway for both air and food.
• Larynx (voice box): found at the lower end of the pharynx. A structure called epiglottis is found covering the larynx. When you breathe, the epiglottis is raised and air flows into the larynx and to the lungs. When you swallow, the epiglottis is pressed down the opening of the larynx to prevent food from entering.
• Trachea (windpipe): a tube at the bottom of the larynx. It is lined with mucus that help prevent dust particles and other things from entering the lungs.
• Lungs: the trachea divides into two branches, each entering a lung. These tubes are called bronchial tubes and they branch into even smaller tubes called bronchioles (singular bronchiole). At the end of each bronchiole is a bunch of tiny air sacs called alveoli (singular alveoli). The exchange of oxygen and carbon dioxide occurs in the alveoli. The absorbed oxygen is transported throughout the body through the blood stream, while the released carbon dioxide is exhaled.