1. Name and describe the function of each structure included onthe human body.

The human respiratory system consists of the nasal cavity, throat (pharynx), voice box (larynx), windpipe (trachea), bronchi, and lungs. Air is taken in through the mouth and the nasal cavity. The nasal passages are covered by thick mucous membranes that contain tiny hairlike projections known as cilia. To keep dust and foreign particles from reaching the lungs, the cilia trap them and sweep them toward the nostrils. The airways from the nasal cavity and mouth meet at a part of the throat called the pharynx. From this point, two passageways open downward, one for food and the other for air. In the upper part of the air passage is the larynx, a box of cartilage that contains a pair of mucous membranes called the vocal cords. The space between the vocal cords is the glottis. When it is open, air passes through the larynx without vibrating the vocal cords. As muscles pull the vocal cords together, they produce sounds. The pitch of the sounds is determined by the closeness and tension of the cords.

The trachea, an open tube of elastic tissue and muscle, extends downward from the base of the larynx. It is coated with a sticky mucous membrane and is kept open by a series of incomplete rings of cartilage. The trachea separates into the two bronchi, each one serving a lung.

As the bronchi enter the lungs, they divide into smaller and smaller branches. The entire network is known as the bronchial tree. The smallest branches, called bronchioles, have muscular walls and can restrict the flow of air if they contract, as happens in asthma. Bronchioles terminate in the tiniest units of all, the alveoli, which are filled with capillaries. Blood carries carbon dioxide to the alveoli and receives oxygen in exchange, which is then circulated to every cell in the body. There are more than 600 million alveoli in the average person's lungs.

2. Discuss how each system works. Follow materials through a system, or show hoe signals, impulses, or substances are controlled, secreted or used.

The oxygen first passes into the nasal cavity which is found right above the mouth. Here a mucus membrane warms and moistens the air. This prevents damage to the delicate lung tissue. The walls of the nasal cavity are lined with cilia that trap foreign organisms and sweep them into the throat so that they can be swallowed. The air then enters the pharynx, which is a tibe at the back of the mouth and nasal cavity. There are two of these tubes, one for air and one for food. When food is swallowed a flap of cartillage called the epiglotis blocks the air passage so no food accidentally goes into the air passage. During inhalation the epiglotis is upright so that air can pass into the trachea. The trachea is between 10 and 12 centimeters long and the walls are lined with cilia. The larynx is located at the upper portion of the trachea. Sounds are made when air is forced between two ligaments that vibrate. The pitch can be varied by the amount of air or the tightness of the vocal cords. From here the trachea branches into two bronchi, each of which leads to a lung. In the lungs the bronchi keep branching into smaller and smaller tubes. The walls are composed of smooth muscle, cilia, and a mucus lining. The bronchioles are lined with mucus and cilia as well. The tubules branch out into sacks of alveoli. Capilaries surround the aveoli and gas change occurs. Each lung contains approximetly 300 million alveoli. After the oxygen enters the blood the carbon dioxide enters the air passages to be exhaled. The oxygen then dissolves in the mucus lining of the aceoli. It crosses both of the thin alveolur membranes and capilaries to enter the blood. Air moving into the alveoli is rich in oxygen, while the capilaries contain high amounts of carbon dioxide. These gases diffuse from higher concentrations to lower concentrations. Carbon dioxide diffuses inti the alveoli and the oxygen into the blood. Blood plasma can carry very little oxygen and so red blood cells containing hemoglobin do most of the absorption of oxygen. Hemoglobin can carry up to four oxygen molecules, which is enough for the body's needs. The oxygen binds to a central iron atom. In this way 97% of the oxygen is transported by blood(hemoglobin). When oxygen reaches the tissues it diffuses into the cell and carbon dioxide diffuses out. 8% is carried away by plasma, 25% to hemoglobin, and the rest is converted to bicarbonate ions which are then carried away by plasma. This process is repeated over and over, even when the body is asleep.

C. Discuss diseases and dysfunctions related to each system.

Respiratory diseases affect the RESPIRATORY SYSTEM, which includes the nose, mouth, throat, larynx, trachea, bronchial tubes, and lungs. These diseases may be acute or chronic and result from a variety of causes, including infections, allergies, tumors, and drug reactions.

Infections are the most common cause of respiratry diseases and may be produced by viruses, bacteria, fungi, protozoa, and microorganisms known as Mycoplasmas and Rickettsias. Viruses are highly communicable from person to person and cause the common head cold (rhinitis) and chest cold. Other viruses cause different types of INFLUENZA such as SWINE FLU, Asian flu, Hong Kong flu, and "Victoria flu." Viruses also cause PNEUMONIA and many other illnesses, including measles, poliomyelitis, and chicken pox, which may be associated with respiratory tract complications.

A large number of bacteria, the most common being species of Streptococcus, Staphylococcus, and Hemophilus, may infect any part of the respiratory system, causing such diseases as sinusitis, bronchitis, pharyngitis, strep throat, tonsillitis, whooping cough, and pneumonia. A bacillus, Mycobacterium tuberculosis, causes TUBERCULOSIS, and other Mycobacteria cause diseases with almost identical symptoms. The latter live in soil and water and are not transmitted from person to person as is the tuberculosis bacillus.

Pathogenic fungi can infect the lungs and cause pneumonialike illnesses such as histoplasmosis, blastomycosis, and coccidioidomycosis. Fungi, which live primarily in the soil and are inhaled into the lungs, are not transmissible from person to person. Actinomycosis and nocardiosis are similar diseases, usually grouped with fungus disorders; they are actually caused by bacteria, however. The true fungus diseases are treated with the antibiotic amphotericin B, whereas actinomycosis responds to penicillin and nocardiosis to sulfa drugs.

Protozoa and other parasites are rare causes of lung diseases in the United States, but an infection known as paragonimiasis, caused by a flatworm known as the lung fluke, is prevalent in the Orient. The hydatid disease, or echinococcosis, is prevalent in Australia, New Zealand, and Argentina and is caused by a cyst-forming tapeworm. A protozoan, Pneumocystis carinii, causes pneumonia in children and occasionally in immunosuppressed adults.

Mycoplasma pneumoniae is a tiny bacterialike organism that causes sinusitis, pharyngitis, bronchitis, and MYCOPLASMAL PNEUMONIA. Infection is spread by close and frequent contact between infected and susceptible individuals; as a result, epidemics tend to occur in schools and military populations. RICKETTSIAS are very small microorganisms having some characteristics common to both bacteria and viruses. They cause Q FEVER, ROCKY MOUNTAIN SPOTTED FEVER, TYPHUS, and other diseases, most of which may be associated with respiratory tract involvement. Infection is spread by the bite of fleas, lice, ticks, or mites.

Allergies are a common cause of respiratory diseases, producing hay fever, asthma, and certain forms of pneumonia. The individual suffering from these conditions has become oversensitive to contact with particular substances such as plant pollen and various types of organic dusts or chemicals. When these agents are inhaled, the body overreacts, producing the symptoms of the specific illness. Allergic pneumonia, also known as hypersensitivity pneumonia, includes such disorders as farmer's lung, caused by exposure to bacteria in moldy hay; bagassosis, caused by exposure to stored sugarcane fibers that has bacterial growth; and air-conditioner or heating-system disease, caused by exposure to bacteria-contaminated mist from humidifiers. Other forms of hypersensitivity pneumonia are pigeon breeder's or parakeet fancier's disease, caused by exposure to a bird protein; and malt worker's lung, caused by exposure to fungi present in barley dust.

Diseases due to inhalation of nonallergenic inorganic dusts are classified as pneumoconioses: silica causes silicosis; coal dust causes BLACK LUNG, or coal worker's pneumoconiosis; asbestos fibers cause asbestosis; and beryllium causes berylliosis. These dusts directly injure the tissues of the lungs and often result in pulmonary fibrosis (scar formation) with resulting impairment of lung function and progressive disability. The pneumoconioses are primarily related to such occupations as mining, sandblasting, and the use of the above substances in manufacturing processes.

TUMORS, which may occur in any part of the respiratory system, can be divided into two groups, benign (noncancerous) and malignant (cancerous). Benign tumors are less serious because they do not spread to other parts of the body, but they may cause damage by local growth and pressure on other structures, producing serious complications such as airway obstruction and bleeding. In addition, they may undergo malignant transformation. Examples of benign tumors are adenomas (now considered low-grade malignancies), hamartomas, lipomas, fibromas, and dermoid cysts.

The most common form of malignant tumor of the respiratory tract is lung cancer, which began increasing in frequency at an alarming rate about 1940; in 1980 it was the leading cause of cancer deaths in men and is also rapidly increasing in prevalence in women. Lung cancer has been attributed to cigarette smoking and environmental pollution: cancer of the lung is rare in nonsmokers, and exposure to materials such as asbestos, chromium, and radioactive substances increases the probability of developing lung cancer. The main types of lung cancer are carcinomas, lymphomas, and sarcomas. Bronchial carcinomas arise from the trachea or bronchi, and alveolar cell carcinomas arise from lung tissue. After developing a carcinoma of the lung, only 5 to 8 percent of individuals survive for 5 years or longer, regardless of the type of treatment that is carried out. Malignant tumors known as lymphomas arise in the lymph nodes related to the lungs and other body tissue. Sarcomas may originate in the lungs or in some other structure such as bone. Sarcomas have a poor prognosis, but recent advances in the treatment of lymphomas, particularly Hodgkin's disease, have increased the chance of cure or at least long-term survival.

Various drugs can cause either pulmonary fibrosis or edema (fluid in the lung). Heroin is probably the most widely used drug that may produce pulmonary edema, but methadone and Darvon overdosage can also cause this condition. Drugs used in the treatment of cancer (methotrexate and bleomycin), leukemia (busulfan), and infection (nitrofurantoin) may cause pulmonary fibrosis.

Structural changes in the lungs or pleura result from a variety of causes, including pneumothorax and bronchiectasis. Pneumothorax is a condition characterized by collapse of the lung due to rupture of the membrane covering the lung and subsequent escape of air into the space between the lung and the chest wall. Pneumothorax may result from penetrating injury to the lung or as a complication of other diseases such as emphysema or pulmonary tuberculosis.

Bronchiectasis is the abnormal dilation of one or more bronchi, usually resulting from weakening of the bronchial wall by infection. This condition may follow pneumonia, whooping cough, or tuberculosis, or may be hereditary. Patients with bronchiectasis usually suffer from a chronic cough, copious sputum production, and occasionally hemoptysis (expectoration of blood).

A vast number of disorders, although not primarily diseases of the respiratory tract, produce major or minor pulmonary manifestations. For instance, sarcoidosis, a tuberculosislike disease characterized by tumorous collections of cells, can involve the lungs, lymph nodes, skin, or any organ of the body. Blood clots originating in the veins or heart can break loose and travel to the lungs, creating a PULMONARY EMBOLISM by obstructing the arteries of the lungs. This leads to damage or death (infarction) of the tissue supplied by the obstructed blood vessel. Immune dysfunction, heart failure, and kidney failure can all affect the proper function of the lungs.

CYSTIC FIBROSIS is a hereditary disease of children and young adults affecting the secretion of the glands that produce mucus, sweat, saliva, and digestive juices. The secretions become viscous, and an abnormally large amount of salt is present in the sweat; the latter characteristic is used as a diagnostic indicator. The disease affects the glands throughout the body, but pulmonary complications are very common.

WHOOPING COUGH caused by a bacteria, Bordetella pertussis, is a children's disease characterized by a high-pitched whooping sound accompanying frequent coughing. This disease may lead to pneumonia and death.

Respiratory distress syndrome (RDS), or HYALINE MEMBRANE DISEASE, is a disorder that occurs exclusively in newborn infants, most often in those born prematurely. It is an indication of incomplete development of the lungs and, as the name implies, the infant suffers from difficulty in breathing and deficient transfer of oxygen from the lungs into the blood. The disease is a leading cause of death in infants. A similar condition in adults, called ARDS (adult respiratory distress syndrome), has many causes, including severe infection, trauma, and the aspiration of stomach contents into the lungs.