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How does blood help to keep us alive? Have you ever wondered what blood is made of, what red and white blood cells do or how the respiratory system (lungs) is connected to the cardiovascular system (hearts and blood)? Well this text will help you answer all these questions. Blood is made up of trillions of cells that need oxygen to live. With out oxygen the cells would die causing the person to die. Plasma makes up 55% of blood, red blood cells make up 44% and white blood cells make up less than 1%. Plasma is a pale yellow liquid which carries all the red and white blood cells, platelets and chemicals around the body. Red and white blood cells will be explained later in the text. Platelets are sticky cells that move around in your blood stream until a blood vessel is injured (when you cut yourself and you start bleeding). Then the platelets join together with a protein called fibrinogen to produce a sort of web to clot the blood vessel. This stops the bleeding which prevents you from loosing blood. Red blood cells are responsible for taking oxygen around the body and picking up carbon dioxide and bringing it back to the lungs. Once the blood has gone through the lungs and picked up the oxygen it circulates all around the body making sure that every spot in your body has enough vitamins, nutrients, oxygen and blood to work properly. When red blood cells go through the lungs they release an iron-containing substance called haemoglobin that picks up the oxygen. White blood cells play the role of the defenders of the body against germs, diseases and illnesses. Some white blood cells move around the body in the blood stream until there is a germ in the body. Then they go to where the germ is and destroy it before it can flow around the body. Other white blood cells produce chemicals called antibodies which stick onto germs making them easier to destroy or get rid of. White blood cells are round with tiny flakes on the surface to help them stick to germs. Have you ever wondered what happens when you breathe in? Well, when you breathe in blood gets pumped out of your heart from the two lower chambers of the heart called ventricles to your lungs where the blood picks up the oxygen that you breathed in. Then the blood travels to all parts of your body through tubes called arteries. After it has gone every where in the body it will return back to the lungs through veins so that the old oxygen can be breathed out as carbon dioxide. Then the cycle starts all over again. Red blood cells with oxygen (Oxygen is the green circle and red blood cells are the red ovals) Germs Plasma White blood cells Platelets surrounding the injured blood cell The heart is one of the main organs in the cardiovascular system. The heart is a muscle and is found to the left of your chest. It is made of a cardiac muscle (a special muscle that contracts rhythmically of its own accord). In the heart there are four chambers. The upper two chambers are called the left and right atrium. The two lower chambers are called the left ventricle and the right ventricle. The two ventricles are the parts of the heart that pumps the blood around the body. The atriums together are called atria. The atria are the parts of the heart that fills up with the blood that has just come from the body and the lungs. The ventricles pump out the blood that will eventually go to the lungs then circulate around the body. The left and right sides of the heart are separated by a thick wall of muscle called the septum. Our heart beats around seventy times per minute when we are relaxed. But have you ever wondered if our heart beat could change speed and beat faster or slower? Here is an experiment that can help you determine how your heart beat changes from when you haven’t done exercise to after you have done exercise. You will need: Stethoscope Place to move around Piece of paper If you do not have a stethoscope you can feel your heart beat (pulse) in your wrist or the side of your neck. If you are having trouble feeling your pulse in those places you can put your hand on your heart and listen really carefully. Steps: 1. Check your pulse and count how many times your hear beats in ten seconds. Then times it by six to get a minute. Then write your first score on a piece of paper. 2. Then do twenty star jumps. 3. Then check your pulse and count how many times your heart beats in ten seconds. Then times it by six to get to a minute. Then write your second score on a piece of paper. How was your first heart rate different from your second heart rate? It was different because there are nerve signals that are sent from the brain that can speed up the brain that can speed up our heart rate if we are doing exercise or if we are stressed. If you want to see if you can get a bigger difference between your first and second score do more than twenty star jumps or do another form of exercise. With out blood our body would have lots of germs flowing around in our blood stream and we would get lots of illnesses and diseases. Also our body wouldn’t get the oxygen, nutrients or vitamins it needs. With out oxygen we can not live. Bibliography: Blood, E.Encyclopedia, Google, Dorling Kindersley Limited, Great Britain, 2006. pp 134-135 (18 April 2010) Kids Health, Heart and Circulatory System, 2010, http://www.kidshealth.org/PageMa nager.jsp? (21 April 2010 Kid Cyber, Heart and blood, 2004, http://www.kidcyber.com.au/topics /body/blood.html (21 April 2010) Britannica, blood, 2010, http://www.k8.eb.com.au/elementa ry/aricle?articleId (22 April 2010) The children’s Heart Institute, Heart, http://www.childrensheartinstitute. org/ , date published unknown, (22 April 2010) Kids Health, blood, 2008, http://www.cyh.com/HealthTopics/HealthTopicsDetails.aspx?p (22 April 2010) 1055 words Picture taken from Encyclopedia Britannica ©2008