2+Human+defence+system


 * [[image:http://blackbyte.homelinux.org/files/files/School/Pharynx.png align="right"]]The Human Defence System in the Blood**

**QUESTION 1**

//**The First Line** // **Physical (non-specific)** //The Skin: // a physical barrier that stops pathogens //Clotting: // if the skin is broken the blood clot stops the entry of pathogens //Sebaceous and sweat glands: // these produce chemicals that kill bacteria //Lysozyme: // this is in the saliva and tear glands and they kill bacteria //Mucous membranes //: these secrete mucus which lines the body parts. The mucous traps the pathogens and prevents them from entering the body //Nasal Hair: // These remove micro-organisms from the air //Cilia: //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt;"> these small hairs beat to force mucus to the pharynx for swallowing to the stomach. Coughing helps this process //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt;">Hydrochloric acid: //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt;"> This is found in the stomach, it kills micro-organisms The main components are Phagocytes (question 3), Macrophages (longer living phagocyte cells, some move around the body and act as scavengers while others remain in a fixed place), Complement defense proteins (substances that are produced y other proteins in response to the presence of foreign materials in the body). If the pathogens get past the first line then the second line steps in.

<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 14pt;">**//The Second Line//** <span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt;">**Specific Defence System** <span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;"> It is call the specific defense system because the system attacks specific invaders. This can happen through making antibodies or white bloods cells engulfing a specific pathogen. White blood cells- Lymphocytes and Monocytes are made by the bone marrow. Then they are transported by the blood to lymph vessels, lymph nodes, the spleen or the thymus gland. //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;">

Monocytes: //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;"> Are white blood cells that become macrophages (large white blood cells). They engulf the invader, once they have done this the invader stay in the microphage. This is called an antigen. //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;">Lymphocytes //<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;">: Some of them attack body cells that contain antigens (part of an invader) on their surface, others produce antibodies. <span style="font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;"> Antibodies- Lymphocytes produce antibodies because of the antigens. These are proteins in a group called immunoglobulins. Each antigen will encourage the production of one specific antibody that will fit into the ‘receptor’ area. That is called natural active induced immunity. It is a protection that is gained against a specific pathogen by creating a specific antibody after the antigen on the pathogen has been found. The Immune System**
 * <span style="color: black; font-family: 'Arial','sans-serif'; font-size: 14pt;">//The Third Line//

<span style="color: black; font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;">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 body systems and cause disease. The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances <span style="font-family: 'Arial','sans-serif'; font-size: 10pt; line-height: 115%;"> The two basic types of leukocytes are:
 * <span style="color: black; font-family: 'Arial','sans-serif';">phagocytes **, cells that chew up invading organisms
 * <span style="color: black; font-family: 'Arial','sans-serif';">lymphocytes **, cells that allow the body to remember and recognize previous invaders and help the body destroy them

The two kinds of lymphocytes are **<span style="font-family: 'Arial','sans-serif';">B lymphocytes ** and **<span style="font-family: 'Arial','sans-serif';">T lymphocytes **. Lymphocytes start out in the bone marrow and either stay there and mature into B cells, or they leave for the thymus gland, where they mature into T cells. B lymphocytes and T lymphocytes have separate functions: B lymphocytes are like the body's military intelligence system, seeking out their targets and sending defenses to lock onto them. T cells are like the soldiers, destroying the invaders that the intelligence system has identified. When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells trigger the B lymphocytes to produce antibodies, specialized proteins that lock onto specific antigens. Once produced, these antibodies continue to exist in a person's body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job. So if someone gets sick with a certain disease, like chickenpox, that person typically doesn't get sick from it again

The immune system is made up of special cells, proteins, tissues, and organs that defends people against germs, bacteria, toxins, parasites and diseases. The cells involved are leukocytes, or white blood cells, which come in two basic types that work together to find and destroy disease-causing organisms and structures. The thymus, bone marrow, and spleen (lymphoid organs) are places in the body where leukocytes are stored and produced. The leukocytes circulate in the body between organs via nodes and blood vessels. By this way, the immune system can track down and prevent the substances that cause diseases and infections. The two basic types of leukocytes are:
 * [[image:immune20system.jpg width="673" height="446"]]QUESTION 2**
 * 1) phagocytes, cells that chew up invading organisms
 * 2) lymphocytes, cells that allow the body to remember and recognize previous invaders and help the body destroy them

A number of different cells are called phagocytes. The most common kind is called the neutrophil, which mainly fights bacteria. Lymphocytes are a kind of white blood cells, which defend the body from various types of diseases and can distinguish the own body's cells from the foreign ones. Before birth, two types of lymphocytes that are produced are B lymphocytes and T lymphocytes. B lymphocytes, or B cells, stay in the bone marrow until they mature. Then, they spread throughout the body and concentrate in the lymph and spleen. T lymphocytes, or T cells, leave the bone marrow and mature in the thymus, a glad found in the chest. Only mature lymphocytes can carry out immune responses.

Several cells work together to indentify and recognize pathogens (disease-causing microbes) and the antigens on them (proteins) when they invade an enter the body. These cells tell the B cells to produce antibodies, specialized proteins that lock onto the antigens. Once produced, the antibodies stay in the body so that if the same type of antigen invades the body again, the antibodies can destroy them. Although antibodies can recognize an antigen and lock onto it, they are incapable of killing the pathogen alone. T cells, or killer cells, help destroy antigens that have been tagged by the antibodies. T cells are also responsible in helping signal other cells (like phagocytes) to do their jobs. Antibodies can also neutralize toxins produced by different microorganisms. They can activate a group of antibodies called complement that is also a part of the immune system. Complement helps in killing bacteria, viruses, or infected cells. All of these specialized cells and tissues of the immune system offer the body against infectious diseases.

When things go wrong with the immune system Disorders of the immune system can be broken down into four main categories:
 * 1) immunodeficiency disorders (primary or acquired)
 * 2) autoimmune disorders (in which the body's own immune system attacks its own tissue as foreign matter)
 * 3) allergic disorders (in which the immune system overreacts in response to an antigen)
 * 4) cancers of the immune system

HIV (human immunodeficiency virus) infection and AIDS (acquired immunodeficiency syndrome).

This disease slowly and steadily destroys the immune system. It is caused by HIV, a virus which wipes out certain types of lymphocytes called T-helper cells. Without T-helper cells, the immune system is unable to defend the body against normally harmless organisms, which can cause life-threatening infections in people who have AIDS.

Autoimmunity - Instead of attacking invaders with antibodies, the immune system components attack the body's own healthy cells, like bones, joints, muscles, as if they were the enemies. When the body reacts this way, it produced auto-antibodies. Some of the illnesses are: autism, autoimmune kidney disease, chronic fatigue syndromes, ect..

__Allergic Reactions__ Allergic reactions and disorders happen when the immune system overreacts to exposure to antigens in the environments. The substances that trigger the allergic reactions are called allergens. The immune system response can cause symptoms such as swelling, watery eyes, itching, and sometimes death.

=Phagocytosis:= <span style="font-family: 'Calibri','sans-serif'; font-size: 11pt;">Your immune system is made of thousands of white blood cells that are used to quickly and efficiently eliminate pathogens. First they find the pathogen because every time it attacks another cell, that cell releases chemical beacons for the white blood to come and stop the invasion. They do this by engulfing the other cell in a process that is identical to the one single cell organisms use to get nutrients. This process is more complex then the endocytosis single cells use to get their nutrients. Phagocytosis requires the white blood cell to do a few more things first. First the white blood cell attaches to the pathogen. It does this by creating a receptor for the pathogen’s surface cells. This makes the cells attach strongly, which makes escape even harder. This also means that the white blood cell need to create a receptor for the surface proteins of the pathogen, meaning that it can only attack threats when it knows what their surface proteins are. This is what makes vaccines so effective, as a weakened strain of the bacteria or virus is injected letting the body learn it’s surface proteins without exposing the person to a big risk.

Flash animation of Phagocytosis: Fullscreen media type="custom" key="6297193" width="532" height="506" align="center"