The circulatory systemHave you ever wondered how the circulatory system works? Me too! It's truly amazing what our bodies do to pump blood (a fluid that carries nutrients) throughout the body to provide energy to the muscles. The circulatory system is the system in our body that is responsible for circulating blood throughout the body. The heart is the central point of the circulatory system. It's almost entirely made up of involuntary muscles, meaning the heart works on its own and the brain doesn't have to tell it what to do. The heart pumps blood throughout the body by twisting. The pumped blood is full of nutrients that the rest of the body needs. The heart pumps about 100,000 times a day, and the brain can tell it to pump more or less blood depending on the body's needs. For example, if you are afraid of an adrenaline rush, the brain must tell the heart to pump more blood in order to provide the body with enough nutrients. Mammals have two main blood circulation systems, pulmonary and systemic. Pulmonary circulation is the system that circulates blood from the heart to the lungs and then back to the heart. In the pulmonary circulation, deoxygenated blood enters the right atrium of the heart and then flows into the right ventricle. From there, blood flows into the pulmonary semilunar valve, which is the only valve that retains deoxygenated blood throughout the body. After that, the deoxygenated blood circulates to the lungs where it becomes oxygenated. For systemic circulation, freshly oxygenated blood enters the heart through the pulmonary veins, which are the only veins to retain oxygenated blood. Blood enters the left atrium through these veins. From there, the blood flows... middle of paper ....... You can get hypertension through: -smoking-obesity-diabetes-sitting too much (at school)-lacking of exercise-too much salt -lack of calcium-lack of vitamin D-too much alcohol-stress (school)-aging-birth control pills-genetics-chronic kidney disease-adrenal and thyroid problems. Atherosclerosis is caused by the buildup of plaque on the artery wall. You can prevent these diseases by eating healthily and getting enough exercise. In conclusion, the circulatory system is a very amazing part of our body. This works perfectly to our advantage and helps us survive. Our bodies are incredible. Score: 33 Works Cited http://www.dummies.com/how-to/content/the-path-of-blood-through-the-human-body.html http://kidshealth.org/ parent /general/body_basics/heart.html http://anthro.palomar.edu/blood/blood_components.htm http://www.medicalnewstoday.com/articles/150109.php