Automobiles require the right fuel and proper maintenance to work properly. Similarly, our bodies need proper care and nutrition to function. If the wrong substances enter the body, they can cause problems with the way the body works. A disease is any condition that disrupts the normal functioning of the body. Disease-causing agents, including certain types of bacteria, viruses, and parasites, are called pathogens. Each type of pathogen invades the body in a different way and causes specific diseases. Once pathogens get inside the body, they produce an infection. Diseases that are caused by pathogens, such as influenza and the common cold, are called infectious diseases.
Pathogens are generally unable to move to a new host on their own. They must be carried in some form from one host to another. A person can be infected with a virus by breathing in the virus-filled saliva that spreads through the air when someone sneezes. Contaminated food can transmit pathogens such as E. coli. Insects, rodents, and other animals can transmit pathogens, as well. Some pathogens, such as human immunodeficiency virus (HIV) and hepatitis, can be transmitted through the blood.
Not all diseases are caused by pathogens. Some diseases are caused by improper nutrition, a lack of exercise, smoking, or alcoholism. Other diseases are passed genetically from parent to child. Such diseases are noninfectious, which means they cannot be passed through the air or by contact with another person. Cardiovascular disease, cancer, diabetes, cirrhosis, and arthritis are a few examples of noninfectious diseases.
The Immune System
The immune system is the body’s defense against pathogens. The defenses may be either nonspecific or specific. The nonspecific defenses of the body help keep pathogens out of the body and the specific defenses fight pathogens after they enter the body.
Nonspecific defenses include the skin, mucous membranes, and inflammation. The skin is a dry, acidic environment unsuitable for most microorganisms. Body cavities exposed to the outside world, such as the nose and throat, are lined with mucus, a sticky liquid that traps germs and other foreign particles before they can invade cells.
Once a pathogen enters the body, for example, through a cut, cells near the injury release chemicals that cause inflammation. These chemicals cause blood vessels to expand and allow platelets to flow through gaps to seal out microorganisms.
If a pathogen gets past the skin or mucus membranes and enters the body, it causes an infection. At that point, the body’s immune system begins to work against the pathogen. The immune system has several unique features that combat pathogens.
First, the immune system responds to specific pathogens. Antigens are proteins located on the cell walls of pathogens that trigger an immune response by the immune system. White blood cells called B cells and T cells that target the specific invader are produced. B cells produce proteins, called antibodies, which attach to the antigens on the pathogen. Killer T cells seek out infected cells and pathogens marked by antibodies and destroy them.
Second, the immune system has the ability to respond to millions of different threats. The B cells that respond to each antigen are present in the bone marrow of a newborn baby. The immune cells are inactive until each one is awakened by the presence of a specific antigen in the body.
Third, the immune system is capable of distinguishing between body cells and cells from other organisms. Immune cells respond to pathogens, cancerous cells, transplanted tissues, and insect venoms. Finally, the immune system is able to remember pathogens and develop immunity, a condition of being able to resist a particular disease.
In the mid-nineteenth century, Louis Pasteur and other scientists discovered that pathogens, commonly called germs, cause many diseases. This discovery was later called germ theory. Doctors learned that washing their hands and using clean surgical instruments could inhibit the spread of disease. Washing our hands is only one way to prevent disease. A healthy, balanced diet, including fruits, vegetables, grains, dairy, and proteins, gives your body the vitamins, minerals, and other materials it needs to function. Eating healthful foods strengthens your immune system and keeps all the systems in your body running smoothly. Foods high in fat, sugar, or salt should be used only sparingly. Obesity is a widespread problem in the United States and contributes to many diseases, such as diabetes and cardiovascular disease. There are other things we can do to prevent disease or catch it in early stages. Regular, aerobic exercise is important to keeping our bodies healthy. Running, walking, swimming, and playing basketball are just a few examples of aerobic exercise.
Alcohol , tobacco , and illegal drugs can. cause many serious diseases. Misuse of prescription and over-the-counter drugs is also harmful to our bodies. Regular doctor visits and routine screenings can help identify problems early. Early treatment can often prevent or slow the serious effects of a disease.
The development of vaccines, which contain weakened, dead, or incomplete portions of pathogens or antigens, was a great step forward in medicine. Vaccines work because the dead or incomplete agents produce the same response in humans that the actual disease does. After receiving a vaccination, the immune system produces a response to the pathogen and creates memory cells against it. Vaccines against polio, smallpox, and measles have saved millions of lives around the world.
Sexually Transmitted Diseases
Sexually transmitted diseases (STDs) such as chlamydia and syphilis are transmitted from person to person during sexual activity. Abstinence, or refraining from sex, is the best way to prevent a sexually transmitted disease. Limiting the number of sexual partners and using condoms can also help prevent STDs.
The United States government organization that oversees public health issues is called the Centers for Disease Control and Prevention (CDC). The CDC works to fight disease and promote health. One of the main goals of the CDC is to prevent an epidemic, a disease or illness affecting a disproportionately large number of individuals. During the fourteenth century, an epidemic of the “Black Death,” a bacterial infection believed to be the bubonic plague, killed about 25 million people worldwide.
The CDC is also tasked with educating the public in ways to prevent disease. You can protect yourself and others from disease in several ways. Covering your mouth when you cough, washing your hands, and keeping surfaces clean are some ways to prevent the spread of disease.