Cardiovascular System - Transporting Fuel and Waste

Blood represents the only tissue in the body that is all fluid in nature. The heart and blood vessels serve as avenues to transport blood throughout the body. Your blood carries necessary nutrients and oxygen to body tissues, and transports metabolic waste and carbon dioxide away from body tissues.

At the center of the cardiovascular system is the heart which creates the pressure necessary to pump blood to all parts of the body through the blood vessels. There are three types of blood vessels: arteries, capillaries and veins. These blood vessels transport the blood to and from organ systems.

The highly specialized, muscular heart serves as a pump that moves blood to the lungs and the rest of the body. The heart has four chambers. There are right and left atrial chambers and right and left ventricular chambers. Each atrium is separated from each ventricle by a cuspid valve that serves to keep blood moving in one direction.

The right and left atria receive the blood into the heart. The right atrium receives blood from the body, and the left atrium receives blood from the lungs. The two ventricles send the blood out of the heart. The right ventricle sends blood to the lungs. The left ventricle sends blood to the body.

The heart manages the blood flow through its four chambers. The right side of the heart, the right atrium, receives oxygen-poor blood from the body and passes it through to the right ventricle. The right ventricle then pumps the blood to the lungs. The lungs remove the carbon dioxide from the blood and replenish the oxygen. The oxygen-rich blood then returns from the lungs to the left side of the heart, the left atrium. The left atrium passes it on to the left ventricle. The left ventricle pumps blood back out to the rest of the body.

Two separate circulation loops exist in the human body: the pulmonary loop and the body, or systemic, loop. The pulmonary loop is the system of vessels that conducts blood from the heart to the lungs and then back to the heart to oxygenate the blood. The systemic loop conducts blood from the heart to all parts of the body to distribute oxygen and nutrients, and then back to the heart.

Arteries carry oxygenated blood toward body systems, away from the heart. Your arteries are lined with thick layers of tissue because of the high pressure of arterial blood and the need for strong structural support. The largest artery in the human body is the aorta, which branches directly off the chamber of the left ventricle of the heart.

Arteries branch out into more and more vessels until they reach the thinnest and smallest of vessels known as capillaries. The walls of capillaries are so thin that gases and other molecules can pass easily across their walls into and back from cells and tissues in the area. This is how the blood distributes the oxygen and nutrients to your body’s cells.

Veins carry blood back toward the heart. These vessels have thinner walls than arteries because blood is under much lower pressure. Venous blood has been depleted of nutrients and oxygen. It is rich in carbon dioxide and returns back to the right side of the heart, where it will be pumped to the lungs for oxygen.

Blood pressure is a measure of the force blood exerts against the wall of a vessel in units of millimeters of mercury (mmHg). Typical blood pressure is measured across the wall of an artery in the arm and is a reflection of high pressure after heart contraction (systole) and lower pressure with heart relaxation (diastole). Therefore, blood pressure is reported as systolic over diastolic and is normally around 120 over 80 mmHg.