The Circulatory System
The human body is made up of many different systems that perform our basic life functions. One such system is the circulatory system. This system transports oxygen and nutrients to organs and tissues within the body and carries away waste products. In performing these functions the circulatory system is associated with other systems in the body. The circulatory system is made up of the heart, blood and blood vessels. The heart is the main component of the circulatory system. It is made up of four chambers, the right and left atrium and the right and left ventricle. The heart's main function is to pump blood through the body. This pumping occurs in two stages each time the heart beats. The diastolic stage occurs when the heart is at rest and the systolic stage when the heart contracts to pump deoxygenated blood toward the lungs and oxygenated blood to the body. Blood is made up of three types of cells: red blood cells, white blood cells and platelets. The red blood cells carry the oxygen to all the cells in the body. The white blood cells fight and destroy germs that can cause disease. Platelets are tiny oval-shaped cells made in the bone marrow. They help in the clotting process. These blood cells are carried through blood vessels in liquid called plasma. There are three types of blood vessels: arteries, veins and capillaries. Arteries carry blood away from the heart while veins carry blood to the heart. Capillaries connect arteries to veins. The right and left halves of the heart act as separate pumps and there is no mix of blood between them. Each half is responsible for pumping blood through one of two blood vessel circuits: the pulmonary circuit and the systemic circuit. In the pulmonary circuit, blood leaves the heart through the pulmonary arteries and goes to the lungs. In the lungs the pulmonary artery divides. Here microscopic vessels pass adjacent to the air sacs of the lung and gases are exchanged across a...
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