Much as our national highways keep traffic moving from city to city, your vascular system keeps blood moving throughout your body. It all starts with the heart, then it moves to the arteries, finally returning to the heart through the veins.

The heart

Your heart weighs between seven and 15 ounces and is only slightly larger than your fist. But this seemingly small muscle provides a powerhouse of activity. Every day it beats an average of 100,000 times and moves 2,000 gallons of blood.

Located slightly to the left of your breastbone and between your lungs, the heart is covered by the pericardium. This is a two-layered membrane. The outer layer attaches the heart to the spinal column and diaphragm with ligaments. The inner layer is connected to the heart itself. Between the two layers is a thin coating of fluid.

To follow the highway idea, your heart is basically the on- and off-ramp for blood. Blood begins its journey on the right side of the heart. Blood then travels to the lungs to be re-oxygenated before returning to the left side of the heart. From there, the newly oxygen-rich blood is sent out to the rest of the body to provide oxygen and nutrients to the organs and tissues.

Eileen Walsh, PhD, APN, RN-BC, FAHA, a Vascular Clinical Nurse Specialist at the Jobst Vascular Institute and an Associate Professor for the University of Toledo's College of Nursing, explains that while the heart is the main pump in the vascular system, it has some help. The diaphragm and the calf muscles also help force blood to move throughout the body.

"The calf muscle contracts and gets blood back up to the heart from the leg veins," Walsh says. "When we take a breath, it also helps move the diaphragm, which in turns helps get the blood flowing through the veins back to the heart."

Arteries and veins

There are two types of blood vessels. Arteries are the blood vessels that carry oxygenated blood away from the heart throughout the body. They carry oxygenated blood to the organs, muscles and tissues of the body. The main artery that takes blood away from the heart is the aorta. Veins return blood that is low in oxygen to the heart where the trip starts all over again.

One exception is the pulmonary artery, which carries blood from the heart through the pulmonary artery into the lungs. Once the blood reaches the lungs, carbon dioxide is removed from the blood. Then oxygen is added back.

There are more veins, however. The structure of arteries is a bit different than veins; artery walls usually have three layers, while veins have only two. Blood within the arteries tends to be at a higher pressure than blood within the veins.

Arterioles and capillaries

Once blood travels from the off-ramp of the heart out to the body through the highway of the arteries, it journeys deeper into your tissues. The side roads that carry the blood there are called arterioles, and the smallest of all are capillaries.

Capillaries drop off nutrients, such as oxygen, and collect waste, like carbon dioxide. Next, they carry the blood into larger blood vessels. These are called venules, which combine to create veins.

"What is unique about veins is they have valves, because we are upright creatures," Walsh says. "Along with the calf muscles, these help propel blood back to the heart." Valves also prevent backward flow in the veins, particularly in the veins of the legs.

If all of your arteries, veins and capillaries were laid out, they would stretch more than 60,000 miles—enough roadway to circle the earth twice.

Vascular health

If one of the routes of the vascular system gets blocked, that's when health problems can happen. Much as a car accident stops traffic, a blockage in an artery can lead to a heart attack or stroke or peripheral artery disease (PAD). "If you have cramping or aching in your legs it could be because you not getting enough blood supply to the foot," Walsh says. "You know when you have chest pain that can lead to a heart attack—it is a pre-warning. In the leg, you can have a symptom called claudication. It is the same as chest pain—a sign of PAD."

"It's also important to make sure you have adequate circulation in the venous side so you don't have leg swelling and don't develop ulcers."

Deep vein thrombosis or DVT occurs when a blood clot forms in a vein and can completely block blood flow. On the road to good health it certainly helps to have a map. Fortunately our bodies provide us with a great network of roads and byways in our vascular system. Understanding how it all works can keep the highways of your heart, arteries and veins flowing freely.

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