Www.cbsd.org



-4762529527500The Lymphatic System and ImmunityThe lymphatic system is an extensive drainage network that?helps keep bodily fluid levels in balance and defends the body against infections. The lymphatic system is made up of a network of lymph nodes, lymph ducts, and lymphatic vessels. These vessels carry lymph, a clear, watery fluid containing protein molecules, salts, glucose, urea, and other substances, throughout the body. One of the lymphatic system's major jobs?is to collect extra lymph fluid from body tissues and return it to the blood. This process is important because water, proteins, and other substances are continuously leaking out of tiny blood capillaries into the surrounding body tissues. If the lymphatic system didn't drain the excess fluid, it would build up in the body's tissues and they would swell.The lymphatic system also helps defend the body against germs like viruses, bacteria, and fungi that can cause illnesses. Those germs are filtered out in the lymph nodes, which are small masses of tissue (most lymph nodes are about 1 cm in diameter) located along the network of lymph vessels. The lymph nodes house lymphocytes (B cells and T cells). Most of the lymph nodes are found in clusters in the neck, armpit, and groin area. Nodes are also located along the lymphatic pathways in the chest, abdomen, and pelvis, where they filter the blood.39052508890 00 One of the major lymphatic vessels is the thoracic duct, which begins near the lower part of the spine and collects lymph from the pelvis, abdomen, and lower chest. The thoracic duct runs up through the chest and empties into the blood through a large vein near the left side of the neck. The right lymphatic duct is the other major lymphatic vessel. It collects lymph from the right side of the neck, chest, and arm, and empties into a large vein near the right side of the neck.Lymphatic tissue is also scattered throughout the body in different major organs and in and around the gastrointestinal tract.How the Lymphatic System Works…1. Carrying Away WasteLymph fluid drains into tiny vessels called?lymph capillaries. The fluid is then pushed along through the capillaries when a person breathes or?the muscles contract. The lymph capillaries are very thin; they have many tiny openings that let gases, water, and nutrients pass through to the surrounding cells, nourishing them and taking away waste products.? When lymph fluid passes through in this way it is called interstitial fluid (fluid located in the microscopic places between cells). Lymph vessels collect the interstitial fluid and then return it to the bloodstream by emptying it into large veins in the upper chest, near the neck.2. Fighting InfectionLymph fluid enters the lymph nodes, where macrophages fight off foreign bodies like bacteria, removing them from the bloodstream. After these substances have been filtered out, the lymph fluid leaves the lymph nodes and returns to the veins, where it reenters the bloodstream.When a person has an infection, germs collect in the lymph nodes. If the throat is infected, for example, the lymph nodes of the neck may swell. That's why doctors check for swollen lymph nodes (sometimes called swollen "glands,” but they're actually lymph nodes) in the neck when your throat is infected.3048000952500Major Organs of the Lymphatic SystemTonsils/ Adenoids- Tonsils are lumps of soft tissue and are part of the immune system. A main function of tonsils is to trap germs (bacteria and viruses) which you may breathe in. Proteins called antibodies produced by the immune cells in the tonsils help to kill germs and help to prevent throat and lung infections. Adenoids are made of similar tissue and they hang from the upper part of the back of the nasal cavity. Like tonsils, adenoids help to defend the body from infection. They trap bacteria and viruses which you breathe in through your nose and they contain cells and antibodies of the immune system to help prevent throat and lung infections.Spleen- The spleen is the largest organ in the lymphatic system. It is an important organ for keeping bodily fluids balanced, but it is possible to live without it. It acts as a filter for blood as part of the immune system. Old red blood cells are recycled in the spleen, and platelets and white blood cells are stored there. The spleen also helps fight certain kinds of bacteria.Appendix- The appendix is a tube-shaped sac that’s attached to the large intestine. The appendix can act as a reserve for good bacteria. After the immune system fends off disease, the good bacteria emerge and re-colonize the gut. Lymphoid tissue accumulates in the appendix after birth. In turn, the appendix helps in the maturation of B lymphocytes and the production of antibodies. The appendix also produces specific molecules that aid in the movement of lymphocytes to various locations within the body.Peyer’s Patches- Peyer’s patches are small masses of lymphatic tissue found in the wall of the small intestine. They form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines.Thymus-The thymus is a lymphoid organ situated in the neck of vertebrates that produces T cells for the immune system.Bone Marrow- Bone marrow is the flexible tissue in the interior of bones and it produces the lymphocytes that support the body's immune system.Lymph Nodes- As stated earlier, lymph nodes are major sites of B and T lymphocytes, and other white blood cells. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles and cancer cells.The Immune SystemThe immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes, problems with the immune system can lead to illness and infection.The immune system is the body's defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade our systems and cause disease.CellsThe cells that are part of this defense system include white blood cells (WBC’s), also called leukocytes. They seek out and destroy the organisms or substances that cause disease. There are several different types of white cells which work together to seek out and destroy bacteria and viruses. All of them start off in the bone marrow, growing from 'stem cells'. The disease-fighting white blood cells are specialists and have a specific job.Among your white blood cells are the following:Neutrophils- They kill and digest bacteria and fungi. They are the most?numerous type of white blood cells and your first line of defense when infection strikes. Monocytes- They have a longer lifespan than many white blood cells and help to break down bacteria. They present pieces of pathogens to T cells so that the pathogens may be recognized again and killed. This causes an antibody response to be mounted. Monocytes eventually leave the bloodstream and become macrophages, the biggest type of white blood cell and their job is to eat foreign material in the body. 3897630107954000020000Basophils- These small cells appear to sound an alarm when infectious agents invade your blood. They secrete chemicals such as histamine, a marker of allergic disease, that help control the body's immune response. Eosinophils- They attack and kill parasites, destroy?cancer cells, and help with allergic responses. Lymphocytes- They create antibodies to defend against bacteria, viruses, and other potentially harmful invaders. There are two kinds of lymphocytes: B lymphocytes (B cells) and T lymphocytes (T cells). Lymphocytes start out in the bone marrow and either stay and mature there to become B cells or leave for the thymus gland, where they mature to become T cells.Functions of B cells and T cells:B cells produce antibodies. Each cell watches out for a particular germ, and when that germ arrives, the B cells starts to produce more antibodies which begin the process of killing that germ. Antibodies attach themselves to the germs so that other cells can recognize that these germs need to be destroyed.T cells look for cells in your body that are hiding invaders (germs) or body cells that are different to normal healthy cells (such as cells that could develop into a cancer) and kill them. There are two different kind of T cells including:Natural Killer T Cells- cell that can react against and destroy another cell without prior sensitization to it.Helper T cells- cells that identify invaded cells and send out chemicals as an alarm, telling killer T-cells to multiply.37242751016000Locations of White Blood Cells (WBC’s)Leukocytes (WBC’s) are produced and stored in many locations throughout the body, including the tonsils, adenoids, lymph nodes, thymus, spleen, appendix, Peyer’s patch, and bone marrow. For this reason, they are called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily in the form of lymph nodes, that house the WBC’s.The WBC’s circulate through the body between the organs and nodes by means of the lymphatic vessels. (You can think of the lymphatic vessels as a type of highway between the rest stops that are the lymphoid organs and lymph nodes.). WBC’s can also circulate through the blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.Here's how it works:A foreign substance that invades the body is called an antigen (think of this as a germ- virus, bacterial infection, etc.). When an antigen is detected, the immune system is activated and WBC’s are sent to determine what has invaded your body. The WBC’s need more specialized cells to help, so they chemically notify the T cells.407479512763500The T cells send for the B cells which have the ability to produce protein strands called antibodies. Antibodies are specialized proteins that lock onto specific antigens. Antibodies and antigens fit together like a key and a lock.Once the B cells recognize specific antigens, they develop a memory for the antigen and will produce antibodies the next time the antigen enters a person's body. That's why if someone gets sick with a certain disease, like chickenpox, that person typically doesn't get sick from it again. This is also why we use immunizations to prevent certain diseases. The immunization introduces the body to the antigen in a way that doesn't make a person sick, but it does allow the body to produce antibodies that will then protect that person from future attack by the germ or substance that produces that particular disease.Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That is the job of the T cells. The T cells that destroy antigens that have been tagged by antibodies or cells that have been infected or somehow changed. T cells are also involved in helping signal other cells to do their jobs.Antibodies can also neutralize toxins (poisonous or damaging substances) produced by different organisms. Lastly, antibodies can activate a group of proteins called complement that are also part of the immune system. Complement assists in killing bacteria, viruses, or infected cells. All of these specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.276622122241000Here is my visual aid to guide you:641356985Germ (antigen) enters the body00Germ (antigen) enters the body370332035560The White Blood Cells are sent to investigate what has invaded your body400000The White Blood Cells are sent to investigate what has invaded your body4808220762100right217170The White Blood Cells need more specialized help, so they notify the T cells 00The White Blood Cells need more specialized help, so they notify the T cells 41224202368550016649702227580The antibodies, with the help of the T cells, go to work to fight off the antigen! += 00The antibodies, with the help of the T cells, go to work to fight off the antigen! += 4027171147510600247459581788000148399537465The T cells send for the B cells because the B cells produce antibodies to fight the germ 00The T cells send for the B cells because the B cells produce antibodies to fight the germ ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download