The Immune System
The Immune and Lymphatic Systems
The human body has a complicated defense system that protects us from disease-causing attackers. An allergic reaction and an inflammation on the skin are some of our body’s reactions that protect us against any invader. When all of our body’s defenses are functioning properly, they work together to keep us healthy and free from diseases. When one or more of these defense systems breaks down, the body may catch some diseases.
The body has three lines of defenses against diseases:
1. the skin and the mucous membrane
2. the white blood cells
3. immunity
These lines of defense attack and fight invaders to protect the body from diseases. When one line of defense does not work well, another one takes over.
Skin and mucous membrane
The skin and the mucous membrane are the first line of defense of our body. They act like guards that prevent dirt and harmful bacteria and viruses from entering the body.
The skin has several layers of defense. Its outer layers of dead, flattened cells provide a natural barrier to the entry of germs. The oil on the skin makes it waterproof and helps prevent the attack of germs. Blood vessels in the skin rush blood to threatened areas to fight growth and development of germs.
Mucous membranes line the organs leading to the digestive and respiratory systems. They protect the body through their secretions. They secrete mucus that traps dirt and disease-causing organisms that may enter the body. The slightly acidic saliva in the mouth and the strongly acidic substances released by the linings in the stomach both keep the bacteria from infecting the body. The mucus secreted by the linings of the nose traps germs. The germs are then swept away by the cilia. With the rhythmic waving motion, they move the dust and germs out of the body.
White Blood Cells
The white blood cells are the body’s second line of defense against diseases. They travel throughout the body. They search and destroy disease-causing organisms like bacteria and viruses.
You can easily tell if your white blood cells are fighting against germs. When you have wound, the nearby blood vessels widen and blood rushes to the infected area. The infected area becomes swollen and red. It usually feels hot and painful. The white blood cells, called phagocytes, in the blood fight the infection by surrounding and destroying the invading germs. Pus is often present at the area of infection. The pus that is discharged contains the fluid serum, white blood cells, and dead and live bacteria.
Immunity
Immunity is the third line of defense. It is the body’s resistance to diseases or foreign substances. To be immune to a disease, our blood must have antibodies. Antibodies are the ones that recognize and destroy foreign substances like bacteria, viruses, and dust.
Some people are born with certain types of immunities. This is the reason why they do not get infected even if they are exposed to disease-causing substances. Other types of immunities must be acquired throughout the life of a person.
Immunity can either be natural or acquired.
There are two forms of natural immunity.
1. Active natural immunity occurs when you get a disease. For example, when you get measles, the immune response begins when the cells of your body are exposed to the measles virus. The first response of your body is to recognize the measles virus as a foreign substance. Then your body starts to make the specific antibodies that will fight against the virus. This immune response is too late to prevent you from getting the measles for the first time. But the antibodies that your body produced when you are sick will protect you from getting measles again in the future.
2. Passive natural immunity is found only in newborn babies. Newborn babies receive antibodies from the mother through the placenta and the mother’s milk. These antibodies protect the body for the first few months of life. Later, the body develops its own immunities.
There are two forms of acquired immunity
1. Active acquired immunity happens when you are given a vaccine. A vaccine is a dose of weakened, living or dead virus or bacteria. An injection of vaccine stimulates your body to produce antibodies against diseases. Most vaccines are given before one gets the disease.
2. Passive acquired immunity happens when you are given a dose of specific antibodies. The antibodies are produced by other persons or animals that were exposed to a similar disease.
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Category: Immune System
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