The cardiovascular system is essentially composed of the heart, the arteries and veins, and the blood. All of these work together to form circulation, which keeps the body working in smooth order.
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The heart is the center of the cardiovascular system; if it is injured or not working properly, then the rest of the system is going to fail also. The heart pumps the blood out to the body through blood vessels. The heart is composed of four chambers; the right atrium, the right ventricle, the left atrium and the left ventricle. Think of a one-way road. Blood comes into the right atrium through the superior vena cava and the inferior vena cava, where it then passes through the tricuspid valve down to the right ventricle. From the right ventricle, it flows up through the pulmonic valve, where it goes to the lungs. After reaching the lungs and ridding itself of the carbon dioxide, oxygen is then taken in, and the blood transports this oxygen-rich blood back through the pulmonary veins to the left atrium. From the left atrium, it makes its way through the mitral valve to the left ventricle, which releases it through the aortic valve to the aorta, where it then flows back out into the body to deliver the necessary oxygen and nutrients.
Arteries carry the nutrient-rich, oxygenated blood out to the rest of the body. Each and every cell in the body receives this. Nutrients may be derived from the intestines or even excess supplies from elsewhere in the body. There are major arteries, such as the aorta, which branches down into the lower parts of the abdomen and branches off in many different places, supplying blood to the extremities and even the head through the carotid arteries. The coronary arteries keep blood flowing through the heart muscle. Major arteries are larger, but to reach all of the tiny cells in the body, they become smaller, and the tiniest ones are called arterioles.
As the blood returns to the heart, it carries with it waste substances, such as carbon dioxide, which is carried from the heart to the lungs where it can be breathed out of the system, and oxygen can be taken back in; other waste products are excreted through the kidneys. Some of the major veins are the venae cavae. The superior vena cava's name gives a hint to where its blood comes from: the upper portion of the body, such as the head and arms. The inferior vena cava brings blood back from the lower part of the body, such as the abdomen and the legs.
Blood is the life of a person, and without it, it is impossible to live. Without blood to rid the body of wastes and carry nutrients and oxygen in, the body would become very ill. Blood helps our bodies fight off illness and can even clot itself when there is an open wound. Plasma is the fluid portion of blood. The more solid parts that make up blood are the red blood cells, white blood cells and the platelets. Red blood cells take oxygen out to all the parts of the body. White blood cells help to fight disease or infection. Platelets are the part of the blood that clot when there is any kind of injury.
Each person has his own particular blood type. The four types are A, B, AB and O. Type O blood can be given to patients having any blood type because it does not have either A or B antigens; therefore it will mesh with the person's blood no matter the type. People with type AB blood can, on the other hand, accept blood from any donor. Our blood type is derived from our genetic history. When the need arises for a blood transfusion, it is imperative that the right blood type be given.