ࡱ;  Root Entry F3DʹCompObjbWordDocumentwObjectPool3Dʹ3Dʹ  FMicrosoft Word 6.0 Document MSWordDocWord.Document.6;  Oh+'0$ H l   D h(C:\MSOFFICE\WINWORD\TEMPLATE\NORMAL.DOT The Lungs Cecilia Chi Cecilia Chi@9ܥe3 ewb( ***tttttt ~ t1f;fTD3* ****>R""**,The Respiratory System The respiratory system is a group of organs inside the thorax. The purpose of the respiratory system is to exchange oxygen for carbon dioxide. When a breath is taken, the air enters the body through the nose or mouth. After this, it travels through the pharynx, the larynx, and the trachea. The trachea splits; one end goes to the right lung, and the other goes to the left lung. These branches are called bronchus. In the lung, each bronchi divides into many smaller branches called bronchioles. These each lead to 8 to 16 alveoli. The pharynx is cone-shaped. It is behind the nose and connects the mouth to the esophagus and larynx, and the nose to the larynx. It is about five inches long. It has two jobs, one to let air to the larynx, and two to let food to the esophagus, and is assisted by the epiglottis. It covers the larynx whenever food comes. On the outside of the pharynx, there are muscles that push food from the mouth to the esophagus. When a person swallows, the pharynx raises to let food through. Otherwise, it is relaxed to let air through. The larynx is between the back of the tongue and the trachea. The vocal cords are in the upper part of the larynx, and it is shaped like a box. This is why it is also called the voice box. In general, the bigger the larynx, the deeper the voice. All the air that is ever inhaled and exhaled always passes through the larynx. It has nine sections made of cartilage. The two most important sections of cartilage are the thyroid cartilage and the cricoid cartilage. The thyroid cartilage forms the Adams apple. The thyroid cartilage makes the side walls of the larynx, and the cricoid cartilage is the back wall. It is also surrounded by rings of cartilage. Without these rings, the trachea would collapse at the first breath. The trachea carries air from the pharynx to the lungs. It is about 4.5 inches long and about 1 inch in diameter. It is fixed in cartilage, and it touches the esophagus. Made of fibrous tissue, it splits into two bronchi, one going into each lung. If something besides air enters the windpipe, it will usually go to the right lung. The trachea is very vulnerable to diseases. The lungs are cone-shaped like the pharynx. Between the two lungs are the esophagus and the heart. They sit on the diaphragm, which separates the chest and abdominal cavities. The right lung has three lobes, superior, middle, and inferior. The left only has two, superior and inferior. This is because the heart beats towards the left, so it needs more space on the left side. At birth, the lungs are pink. As they get older, they will turn gray and spotted. The more smoky the environment, the more gray and spotted they will be. The lungs are surrounded by a thin stretchy film called the pleura. If they are healthy, they should float in water. When they are infected with a disease, they will sink. The lungs can hold about four quarts of air. In normal breathing, only one pint of air is inhaled per breath, or about one twentieth of the lungs capacity. When doing exercise or just active in some way, in one breath about six pints are inhaled. After the pint inhaled is exhaled, three pints more can be forced out. After this, there is still about one pint left that cannot be exhaled. This air is called alveolar air. Because of the high amount of blood in the nose, mouth, and pharynx, the incoming air is warmed to body temperature and adjusted to body humidity. The alveoli are where the exchange between oxygen and carbon dioxide takes place. At the end of each bronchiole, there is a bunch of alveoli, like grapes. There are an estimated three hundred million alveoli in each lung, but each one is only about 1/70 to 1/200 of an inch in diameter. They are what make up the lobes in each lung. Alveoli are each surrounded by many small capillaries, which take oxygen from the alveoli. They release carbon dioxide, which is then exhaled. A very important organ in breathing is the diaphragm. The diaphragm is a powerful dome-shaped muscle. It, along with rib muscles, contract during inhalation. This means there is more room for the lungs, so the pressure inside drops, and once it drops below atmospheric pressure, air goes in. It is made up of mostly muscle, which surrounds the tendon in the center. Made of bone, cartilage, and muscle, the thorax holds almost all of the respiratory system. It is shut off from outside of the body and the rest of the body, besides the trachea from the lungs and from blood vessels. This way, the atmospheric pressure is maintained at the right level. If the thorax was punctured, the lungs would collapse. The cleaning system in the lungs has four parts. The cells around the trachea trap dust and bacteria. The cilia unclog air paths from mucus. Chemicals, unnecessary mucus, and large bits of alien matter are thrown out with a cough. Macrophages are the fourth defense, which swallows or dissolves anything that reaches the alveoli with enzymes.  throat  voice box  windpipe  air sac  leaf-shaped cap above larynx  tiny lashes like hair ࡱ; SummaryInformation(ǹ@S1@ʹ@DʹHA@8Microsoft Word 6.017ࡱ; *+<=/0IJ uDPuDPccU^c2E Sm3!H!!! !!!!!!!!!!!!!!!hhK@Normala "A@"Default Paragraph Font@ Footnote Text &@ Footnote Referenceh*</I  *IadIId   (+  , Cecilia ChiC:\MSOFFICE\WINWORD\LUNGS.DOC@Epson Stylus 800+LPT1:epepstEpson Stylus 800+ D"'hhEpson Stylus 800+ D"'hhaaaa1Times New Roman Symbol &Arial"h,eiAHAPi "$3 The Lungs Cecilia Chi Cecilia Chiࡱ;