The cardiovascular system is a complex network of the heart, blood vessels and blood. It's job is to deliver nutrients to the body and remove byproducts from the tissues. At the center of the cardiovascular system is the heart--a four chambered pump that dispenses blood to the arteries. The arteries carry nutrients and oxygenated blood to the body's tissues. The veins return de-oxygenated blood to the heart, where the cycle repeats itself thousands of times a day.
The heart is a muscle about the size of an adult fist. It is composed of two sides and four chambers: the left and right atria and the left and right ventricles. The two atria are located on the top of the heart and receive blood from various parts of the body. The two ventricles are located on the bottom of the heart and pump blood away from the heart, to the body. The right ventricle is responsible for pumping deoxygentated blood to the lungs. The left ventricle pumps oxygenated blood to the rest of the body. Between the chambers are valves. Valves control the flow of blood, insuring that it flows in one direction.
The Blood Vessels
Blood vessels are a series of elastic tubing that carry blood to and from the heart. Oxygenated blood leaves the heart and supplies oxygen and nutrients to the body via the arteries. After crossing capillaries, veins return deoxygenated blood and waste products to the heart through the vena cava. After leaving the right ventricle through the pulmonary arteries, the blood gets oxygenated in the lungs, disposes of carbon dioxide from the body, returns to the left atrium from the pulmonary vein and then to the left ventricle to repeat the process again.
Blood is a semi-viscous fluid that contains red blood cells, white blood cells, platelets and a watery substance called plasma that contains proteins, sugars, fats and minerals. The average adult body circulates 10 pints of blood through a cardiac cycle. The red blood cells contain hemoglobin, which is responsible for transporting oxygen to the cells and carries carbon dioxide back to the heart.