1. The SINUSES (frontal, maxillary, and sphenoidal) are hollow spaces in the bones of the head. Small openings connect them to the nose. The functions they serve include helping to regulate the temperature and humidity of air breathed in, as well as to lighten the bone structure of the head and to give resonance to the voice.
2. The NOSE (nasal cavity) is the preferred entrance for outside air into the respiratory system. The hairs that line the wall are part of the air-cleaning system.
3. Air also enter through the MOUTH (oral cavity), especially in people who have a mouth-breathing habit or whose nasal passages may be temporarily obstructed, as by a cold or during heavy exercise.
4. The ADENOIDS are lymph tissue at the top of the throat. When they enlarge and interfere with breathing, they may be removed. The lymph system, consisting of nodes (knots of cells) and connecting vessels, carries fluid throughout the body. This system helps to resist body infection by filtering out foreign matter, including germs, and producing cells (lymphocytes) to fight them.
5. The TONSILS are lymph nodes in the wall of the throat (pharynx) that often become infected. They are part of the germ-fighting system of the body.
6. The THROAT (pharynx) collects incoming air from the nose and mouth and passes it downward to the windpipe (trachea).
7. The EPIGLOTTIS is a flap of tissue that guards the entrance to the windpipe (trachea), closing when anything is swallowed that should go into the esophagus and stomach.
8. The VOICE BOX (larynx) contains the vocal chords. It is the place where moving air being breathed in and out creates voice sounds.
9. The ESOPHAGUS is the passage leading from the mouth and throat to the stomach.
10. The WINDPIPE (trachea) is the passage leading from the throat (pharynx) to the lungs.
11. The LYMPH NODES of the lungs are found against the walls of the bronchial tubes and windpipe.
12. The RIBS are bones supporting and protecting the chest cavity. They move to a limited degree, helping the lungs to expand and contract.
13. The windpipe divides into the two main BRONCHIAL TUBES, one for each lung, which subdivide into each lobe of the lungs. These, in turn, subdivide further.
14. The right lung is divided into three LOBES, or sections. Each lobe is like a balloon filled with sponge-like tissue. Air moves in and out through one opening -- a branch of the bronchial tube.
15. The left lung is divided into two LOBES.
16. The PLEURA are the two membranes, actually one continuous one folded on itself, that surround each lobe of the lungs and separate the lungs from the chest wall.
17. The bronchial tubes are lines with CILIA (like very small hairs) that have a wave-like motion. This motion carried MUCUS (sticky phlegm or liquid) upward and out into the throat, where it is either coughed up or swallowed. The mucus catches and holds much of the dust, germs, and other unwanted matte that has invaded the lungs. You get rid of this matter when you cough, sneeze, clear your throat or swallow.
18. The DIAPHRAGM is the strong wall of muscle that separates the chest cavity from the abdominal cavity. By moving downward, it creates suction in the chest to draw in air and expand the lungs.
19. The smallest subdivisions of the bronchial tubes are called BRONCHIOLES, at the end of which are the air sacs or alveoli (plural of alveolus).
20. The ALVEOLI are the very small air sacs that are the destination of air breathed in. The CAPILLARIES are blood vessels that are imbedded in the walls of the alveoli. Blood passes through the capillaries, brought to them by the PULMONARY ARTERY and taken away by the PULMONARY VEIN. While in the capillaries the blood gives off carbon dioxide through the capillary wall into the alveoli and takes up oxygen from the air in the alveoli.
