The human body is made of cells that group into tissues that form into organs. All cells of the body require nutrients and the nutrients are delivered by the blood. The blood travels through the body in complex system of vessels including arteries, veins and capillaries. There are so many vessels in the body that if pulled apart and laid end to end they would stretch for 60,000 miles, enough to circle the earth twice according to information provided by the Texas Heart Institute. The cardiovascular system consists of three major parts; these vessels, the heart and the blood.
Heart
The human heart, which weighs less than a pound, provides the power required to sustain life. From the very first beat, it works continually without ever pausing, beating approximately 2.5 billion times in an average lifetime according to The Franklin Institute.
The heart contains four cavities; two aortas at the top and two ventricles at the bottom. The right aorta is connected to the right ventricle with a valve, called the tricuspid valve that allows the flow of blood between them. The left aorta is connected to the left ventricle with the mitral valve. The heart is made of muscle, called the cardiac muscle that contracts between 70 to 80 times a minute.
Blood
The power provided by the contractions of the heart propels the blood through the body. Just as the heart provides the power for life, it is the blood that is the fluid of life. Blood is responsible for carrying oxygen and essential elements to all the cells as well as removing waste from the cells.
There are several components to blood. The plasma is the clear-colored liquid portion that accounts for 55 percent of the total blood as reported by the Franklin Institute. The remaining part of blood is made up of living cells. Red blood cells are the cells responsible for carrying oxygen from the lungs to all tissues. White blood cells protect the body from foreign invaders and provide the body with immunity. Platelets are cells that cause the blood to clot, which is necessary to prevent bleeding to death.
Blood Vessels
The heart pumps the blood but the final component of the cardiovascular system are the blood vessels, which are the tubes through which the blood travels. Without them the blood would not know where to go and cells would not be nourished. The blood vessels are like tiny one-way highways allowing blood to flow in an organized pattern.
Arteries carry oxygen-rich blood away from the heart to the tissues and cells. The human body contains 20 major arteries; the largest is the aorta that connects to the heart. These arteries branch into small vessels called arterioles. Arterioles branch off further into the tiny capillaries that supply the blood to the cells. The blood carrying the carbon dioxide from the cells returns to the heart through veins.
