The cardiovascular system, or circulatory system, is primarily responsible for transport. It moves oxygen from the lungs to the tissues, removes waste products from the tissues to organs of excretion, provides nutrients necessary for metabolism and transports hormones to the necessary cells and tissues. The circulatory system also assists in regulating body temperature and plays a role in protecting the body from disease by participating in immune function. While there are many components that make up the cardiovascular system and help control it, there are four main parts.
Heart
The human heart is a cone shaped muscular pump about the size of a person's fist. It is located just left of center in the chest. The primary function of the heart is to pump or circulate blood throughout the body. The American Heart Association notes that the heart is comprised of four chambers; the right and left atrium and the right and left ventricle. Blood is pumped through these four different chambers of the heart and, because of valves located between each chamber, blood is only able to move in one direction. This allows for circulation throughout the body. Oxygen rich blood arrives from the lungs to the left side of the heart and is then pumped out to the tissues where it deposits oxygen and other nutrients. De-oxygenated blood is then circulated back to the right side of the heart, where it is pumped to the lungs to collect more oxygen. According to the Mayo Clinic, an average heart beats about 100,000 times a day, or about 70 times a minute. The heartbeat is controlled by electrical impulses that are generated by a very specific tissue, called the sino-atrial node, which is the pacemaker of the heart.
Blood
Blood is a fluid that circulates through the vessels and heart. It is actually a connective tissue, but is unique because it is fluid. As blood travels from the heart to the lungs and other tissues, it carries oxygen, other nutrients, hormones and waste products-transporting them to the appropriate locations. According to the Franklin Institute, the average adult has approximately five liters of blood in the circulatory system. The blood contains living cells that are constantly reproducing. Red blood cells help transport oxygen and white blood cells assist in immune function. About 55 percent of blood is plasma, a clear, yellowish liquid that contains solid cells and platelets that assist in blood clotting.
Arteries
Arteries are hollow vessels that transport blood away from the heart. The largest artery, the aorta, is the main vessel that carries oxygenated blood out of the heart. Pressure is generally quite high in arteries and according to CancerIndex.org, the walls of arteries are elastic to assist in the pumping or circulation of blood.
Veins
The veins are blood vessels, similar to arteries, that transport blood to the heart under low pressure. They have thinner walls and are less elastic.
