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The Immune system is the body’s overall defense system against harm causing invaders, that come from the outside world, that are able to inter the body one way or another. The immune system is not an organ or two that do all the work, but rather a network of parts all throughout the body that works with other bodily systems to fight off viruses, diseases, infections, and anything that the immune system knows does not belong in the body.
A pathogen is any organism or virus that can cause a disease after entering the body. The first line of defense against pathogens are external barriers such as the skin. The nose has nostril hairs act like a filter for elements entering the body through the nose. The nose can also fill with mucus that can exit the body to get rid of any pathogens that might enter the nostrils. The eyes have eye lashes that can wave away pathogen’s when a person blinks. The average person blinks about 16 times a minute. That is typically enough to keep out pathogens floating in the nearby air. According to Campbell Essential Biology with Physiology 4th Edition (2012):
External barriers also include chemical defenses in the form of antimicrobial secretions. Sweat, saliva, and tears contain enzymes that disrupt bacterial cell walls. Glands produce oils and acids that make the skin inhospitable to many microbes. Concentrated stomach acid kills most of the bacteria we swallow before they can enter the bloodstream. (p. 518)
External barriers make up the first line of defense. When a pathogen does make it passed the barriers, it is now up to the internal immune system to fight it off. This is the second line of defense. Phagocytic cells are white blood cells that are able to consume foreign cells or pathogens, thus killing them. Another type of white blood cell that can kill off pathogens or infected cells are NK cells, or natural killer cells. These NK cells will discharge chemicals that kill infected cells. The body has another natural defense, which are defensive proteins. When a virus is successful in infecting a cell, the cell may release interferon molecules. These interferon molecules bind themselves to nearby healthy cells. The binding of interferon molecules to healthy cells prompts the healthy cell to produce antiviral proteins. Other natural defensive proteins that our immune system creates are complement proteins, which attack pathogens directly. (Simon, 2012, p. 519)
The lymphatic system is a system of vessels and many lymph nodes that are crammed within white blood cells. Other lymphatic system organs include the tonsils, thymus, and the spleen. “The two main functions of the lymphatic system are to return tissue fluid to the circulatory system and to fight infection.” (Simon, 2012, p. 520) The lymphatic system works in conjunction with the circulatory system. For example, when someone gets a paper cut from a dollar bill, the dollar bill introduces bacteria into and under the skin. The first line of defense has already been penetrated. The lymphatic system will pick up on chemical signals that the skin has been torn, then send white blood cells via the arteries of the circulatory system to the paper cut site. The white blood cells will engulf the bacteria and cell debris, allowing the tissue to heal.
If all the above fail to keep the body healthy, there is also a third line of defense, called adaptive defenses. “Adaptive defenses depend on white blood cells called lymphocytes that recognize and respond to specific invading pathogens.” (Simon, 2012, p. 521) These lymphocytes blood cells are triggered only after exposure to specific pathogens. The innate defenses are constantly prepared to combat a variation of infections, but lymphocytes must be primed by exposure to a foreign molecule. Any molecule that elicits a response from a lymphocyte is called an antigen. (Simon, 2012, p. 521). There are two types of lymphocytes cells, the first one is called the B-cell, and the second one is called the T-cell. One very interesting thing about this cells is how they develop. Both B-cells and T-cells form within bone marrow. The B-cells grow to maturity in the bone marrow, but the T-cells start in the bone marrow and are transported via blood to the thymus to finish growing to maturity. Paul A. Linnemeyer wrote:
Macrophages are important in the regulation of immune responses. They are often referred to as scavengers or antigen-presenting cells (APC) because they pick up and ingest foreign materials and present these antigens to other cells of the immune system such as T cells and B cells. This is one of the important first steps in the initiation of an immune response. Stimulated macrophages exhibit increased levels of phagocytosis and are also secretory. (p. 1)
It is very important the that the immune system functions well for the health of all human internal systems. If a pathogen that infected the digestive system entered the body and the immune system was not able to fight it off, it could cause damage to the digestive system to the point where the body could not digest food and therefore not get the nutrients needed to keep the body alive. If a pathogen that infected the respiratory system got into the body and the immune system could not fight off, it could affect the body’s ability to oxygenate its cells and cause the death of the person even though the pathogen itself may not be able to cause death. Likewise with the circulatory system. This clearly shows that a healthy immune system is a critical system to have, to keep internal systems healthy, which in turn keep the person healthy.
As a result of having a low immune function, your body would have a harder time fighting off virus such as the cold and flu viruses, causing the symptoms to last longer. Infections can cause damage to the immune system, which further inhabits resistance to pathogens.
HIV is a virus that causes acquired immune deficiency syndrome (AIDS) There are treatments for AIDS, but no cures. People living with AIDS tend to have to change their life style. When someone first finds out that they are HIV positive there can be a wide range of feelings including of anger, sadness, depression fear, anxiety. This can cause much stress or the carrier of the HIV virus and their families. In some cases having or treating AIDS can affect the brain. This can cause clumsiness, sudden shifts in behavior, difficulty paying attention, and forgetfulness, among other problems. (University of California, August 03, 2011)
In conclusion, The immune system is one of the most important systems in the human body. The immune system can interact with other bodily systems in a variety of ways. The immune system has three primary lines of defense, the exterior barriers, the internal innate defenses, and the internal adaptive defenses. Without an immune system, humans would die very easily due to many things. But with an immune system, humans can hope to survive and thrive despite the many things that can infect them.
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