| Terence Lee's Science Page | ||||||||||||||||||||||||
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Hi! My name is Terence Lee. I love science and that is why I made this page. This Science Page is all about science. You will love it. You will be able to find many informantion. Enjoy! | |||||||||||||||||||||||
| This Part is about the circulatory system! | ||||||||||||||||||||||||
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A human body is made of of systems. Each system is made of organs and each organs are made of tissues. This part will tell you about the Human Circulatory System, one of the most important systems. Parts of the Circulatory System There are many parts in the circulatory. The main part is the heart. The heart connects to blood vessels- arteries, veins and capillaries. The arteries are blood vessels that take blood away from the heart and to the tissues and organs of the body. There are three layers in the arteries, the adventitia, which is the outside of an artery, the media, which is the middle layer, and the endothelium, which is the inside layer. Veins are blood vessels that bring the blood back to the heart. Veins also have three layers but the walls are much thinner. Capillaries connect the smallest arteries, which are the arterioles, and the smallest veins, which are the venules. There are many kinds of arteries and veins. The pulmonary arteries bring the deoxygenated blood to the lungs. As it passes the lungs, the blood collects the oxygen. The pulmonary veins bring the oxygenated blood back to the heart. The aorta is the largest artery. It is shaped like a cane. It receives blood from the left ventricle. The coronary artery supplies the heart with blood. The aorta divides after leaving the heart and brings the blood back to the heart. The superior vena cava is a vein that collects the blood from the head, neck, and arms. The inferior vena cava is a vein that collects blood from other parts of the body. These veins carry the blood to the right atrium. The femoral arteries are blood vessels that supply the legs with blood. The aorta branches off into two iliac arteries. Each of the iliac arteries then becomes femoral arteries. The femoral vein is an artery that takes the blood away from the legs. The blood it collects are passed on to the iliac veins and then to the inferior vena cava. The jugular vein is one of the three main veins that drain the blood out of the head and toward the heart. The carotid arteries are different from other arteries of the circulatory system. Other arteries of the body are deep in the body, where the muscles protect the blood vessels. But the four carotid arteries lie just below the surface of the neck, next to the trachea, which is a windpipe from the respiratory system. They supply oxygen to the brain. If the carotid arteries are injured, the person might get unconscious. The brachial arteries are arteries that supply the arms with blood. The main artery that supplies the arms starts as the subclavian artery. It then becomes the axillary artery as it goes through the armpit or axilla before it becomes the brachial artery. The radial artery is one of the many branches of the brachial artery. The hepatic artery gives the liver oxygenated blood and the hepatic portal vein gives the liver blood full of nutrients. Blood vessels don't just carry blood. They also carry cells. A drop of blood may contain 250 million cells. Blood contain many kinds of cells such as red blood cells. The red blood cells are full of oxygen and they give blood its red color. Blood also contains white blood cells. These colorless cells are part of the body's immune system. They help destroy microorganisms by engulfing them. They also help fight diseases. Plasma is a yellowish liquid found in the blood. This liquid takes up 55% of the volume of the blood. Vessels also carry other things besides cells such as hormones. The circulatory is a very important system in your body. Many people say to stay alive for a long time you must get healthy. So try not to eat foods with too much fat or cholesterol. | |||||||||||||||||||||||
| The Immune System | ||||||||||||||||||||||||
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You will learn about the Immune System in this part. | Immune System The immune system is the human body's defense against foreign substances such as microorganisms. The immune system is essential for survival providing recovery from a virus. The immune system is made up of white blood cells. White blood cells often grow in the lymph system. There are more than a thousand different cells. A major function of the immune system is surveillance of the cells of the body to make sure no cells are attacked by foreign substances. Bacteria or any other kinds of viruses come into the human body when there is a cut and when the organism inhales. You can sometimes see pus. Pus is a yellowish, oozy substance usually seen in a cut. It usually means that the immune system is working. Pus is a combination of both dead germs and damaged cells. When bacteria enters the body, it immediately attacks nearby cells. But the body is quick to respond. The body's response to an attack on its cells is called an inflammation. In the process of inflammation, the quickest thing that happens is an increase supply of blood to the infected area. This will make the infected area look really red or swollen. Immune responses are not always beneficial. When the immune system attacks the foreign substance or antigen, it maintains a memory of the event so the next time that antigen comes to attack the body, your white blood cells can destroy them faster. If the infected person or organism produces a toxin, the organism would most likely get a fewer or an increase in the body temperature. Some scientists now think that an increase in body temperature helps to stop the growth and reproduction of many disease-causing organisms. A fever is actually a sign that the human body's immune system is working. The immune system has two general types of responses, the antibody and the cellmediated responses. The cell-mediated immunity is also known as cellular immunity. It is used against most viruses. White blood cells produced in the liver, spleen, and bone marrow are called lymphocytes. The B cells and T cells are lymphocytes. There are about one trillion B cells and one trillion T cells in a person's body but not all of them survive. The B cells grow in an organism's bone marrow. There, they develop receptors. The receptors help the B cells recognize and destroy antigens. When an invader appears the B cells turn into plasma cells. The plasma cells release the right antibodies, which lock onto the antigen and disable the bacterium. The antibodies are also called immunoglobulins. Then, the B cells become a memory cell, which helps them memorize the antigen. The next time the antigen comes back again, the B cells reproduce itself, making duplicates of the cells that have the right antibodies. T cells develop in the organism's thymus gland found in the person's chest. Unlike the B cells, they attack the invaders instead of producing antibodies. There are three main types of T cells: the killer T cells, the helper T cells, and the memory T cells. They do different things that are similar to the work B cells do. The T cells usually travel through the bloodstream. The killer cells look for infected cells and then lock onto them like immunoglobulins do. They also release chemicals called lymphokines, which help destroy the infected cell. Helper T cells assist the killer T cell and help B cells produce antibodies. Memory T cells memorize the antigen so an invader can destroy much faster in the future. T cells and B cells work together to destroy foreign substances. Lymphocytes can also be found in the lymph nodes. Lymph nodes are also known as lymph glands. They are made of masses of lymph tissues. There are also sinuses, which are also spaces, contain many macrophages that eat the foreign substances. The germinal center releases lymphocytes and the trabecula divides the node into segments. The efferent lymph vessel carries filtered lymph, a watery liquid, away from the lymph node and the afferent lymph vessel brings the lymph to the lymph node. Mostly the immune system attacks foreign substances. But sometimes it confuses the body's proteins with antigens and starts attacking its own cells. This is called autoimmunity. Most of the time the body's cells destroy the antigens, but not always. A virus can reproduce themselves in cells. When a virus enters a cell, it releases the materials it needs to clone itself. Then the cells reproduce the virus instead of the cells. The viruses then leave the infected cell and move on to another healthy cell and keeps on multiplying. There is a virus called AIDS, which stands for Acquired Immune Deficiency Syndrome. It is an illness. AIDS is caused by HIV. HIV stands Human Immunodeficiency Virus. HIV is a spherical virus. Its genetic material is composed of RNA, or ribonucleic, acid along with enzyme called reverse transcriptase. RNA is a nucleic acid that handles the information used to make proteins. The center has a shell that has proteins known as P24 and P18. Around the shell is a membrane of a certain kind of material called lipid. Around the lipid membrane is a membrane of glycoprotein 120 (GP120). When HIV invades a cell, it releases its RNA and enzyme into the cell. The enzyme then enables the viral RNA to make a strand of viral DNA. The viral DNA enters the nucleus of the cell and combines its own kind of material, forming a provirus. The cell then produces a new viral DNA from the provirus. They become new HIV. HIV can be spread through sexual intercourse or contaminated blood. If HIV is spread to the brain or other parts of the nervous system, the person may have mental problems. The person, whose immune system is destroyed by HIV, might have lung infection such as pneumocystis carinii pneumonia or PCP. AIDS can attack the part of the defense system that destroys invading germs or bacteria. AIDS virus can penetrate or go through T cells and the cell would clone the virus instead of itself. The T cells are then destroyed and the immune system would weaken. The immune system would not be able to fight against other bacteria and germs. A person can then die from the microorganisms. It is believed that an organism can die approximately 10 years from the time it was first attacked by AIDS. Bacteria are also dangerous. Instead of multiplying in a cell, it just reproduces by dividing in half. Before antibiotics were invented, bacterial infections were often deadly. Your immune system can also overreact. If a certain kind of foreign substance gets into the body that the person is allergic to, the immune system treats them like something really dangerous. Some lymphocytes then start to produce a lot of antibodies. Those cells release a chemical substance called histamine. If this chemical is released, it causes itching and the release of fluids. If the person's immune system isn't working, a person can have many diseases such as heart diseases and cancer. Researchers say that the immune system produce antibodies that attack cells that carry away cholesterol. If these cells were destroyed, the cholesterol would be trapped in the blood vessel walls. It would harden vessels and clog arteries and cause heart attacks. So heart attacks are really caused by the immune system. The human body can have some sick cells. They change instead of dying. They can reproduce very quickly. The body will then have a lot of these sick cells, which are also called cancer cells. The immune system does try to destroy them. The cancer cells are usually destroyed. But sometimes the immune system misses a sick cell. Then cancer develops. The defense system does fight the cancer and most of the time it is able to decrease the growth of cancer. Researchers recently found a protein called interferons. These proteins interfere with the growth of cancer cells. Interferons can be made in a lab. This means that a lot of people will survive from cancer. But too much of it isn't good and it could be dangerous. Now scientists are now trying to find a way to use these helpful proteins. The immune system is very helpful. It is needed a lot of times. Most people have an immune system, but unfortunately some people don't, like Bobby and James. They had to live in an artificial world where they couldn't touch any human, not even their parents. Where they lived had to be germ free. They were not allowed outside in the world. Both Bobby and James suffered from combined immunodeficiency disease. Those who have this disease are born without T or B lymphocytes. Most people who are born without any immune system die when they are young.
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