Blood Vessels

What are blood vessels?

Blood vessels are channels that carry blood throughout your body. They form a closed loop, like a circuit, that begins and ends at your heart. Together, your heart and blood vessels form your circulatory system. Your body contains about 60,000 miles of blood vessels.

There are three main types of blood vessels:

• Arteries
• Veins
• Capillaries

What do blood vessels do?

The function of blood vessels is to deliver blood to the organs and tissues in your body. Blood supplies them with the oxygen and nutrients they need to work. Blood vessels also carry waste products and carbon dioxide away from your organs and tissues.

Each type of blood vessel serves a different function:

• Arteries. These strong, muscular blood vessels carry oxygen-rich blood from your heart to your body. This blood contains oxygen from your lungs.
• Arterioles. Similar to arteries, arterioles are smaller branches that extend out from arteries as they move toward your tissues. These smaller vessels are very flexible. They get bigger or smaller to help maintain your body’s blood pressure.
• Capillaries. Your smallest blood vessels, these connect arteries and veins. Because of their thin walls, capillaries are transfer stations for oxygen, nutrients, carbon dioxide and waste.
• Venules. Venules (small veins) receive blood from capillaries and lead to veins.
• Veins. These blood vessels carry oxygen-poor blood back to your heart. From there, it goes to your lungs for more oxygen.

Where are blood vessels located?

Blood vessels run all through your body. Branches from large vessels get smaller and smaller, reaching every organ in your body. You have billions of blood vessels in your body, and most of them are capillaries, venules and arterioles. These smaller vessels connect to 160 arteries and 200 veins.

Your most important blood vessel is your body’s main artery — your aorta. This is a large artery that carries blood away from your heart and delivers oxygen-rich blood to your body. Your aorta runs down through your chest, diaphragm and abdomen (belly), branching off in many areas. Near your pelvis, this main artery branches into two arteries that supply blood to your lower body and legs.

The main vein in your body is the vena cava. The superior vena cava is in the upper right part of your chest. It takes blood from your head, neck, arms and chest back to your heart. The inferior vena cava is near the right side of your diaphragm. It brings blood from your legs, feet, abdomen and pelvis back to your heart.

What are the parts of blood vessels?

Blood vessel anatomy includes three layers of tissue:

• Tunica intima. This inner layer surrounds the blood as it flows through your body. It regulates blood pressure, prevents blood clots and keeps toxins out of your blood. It keeps your blood flowing smoothly.
• Media. The middle layer contains elastic fibers that keep your blood flowing in one direction. The media also helps vessels expand and contract.
• Adventitia. The outer layer contains nerves and tiny vessels. It delivers oxygen and nutrients from your blood to your cells and helps remove waste. It also gives blood vessels their structure and support.

What do blood vessels look like?

Blood vessels have a tube-like shape, but they rarely run in a straight line. Some are big enough to see under your skin. If you’ve ever had your blood drawn, you may have noticed veins on the inside of your arm. They might appear blue under your skin, even though your blood is red.

What are the common conditions and disorders that affect blood vessels?

Many different problems can affect your blood vessels, including:

• Aneurysm. A bulge or outpouching in a weak or damaged part of an artery. Aneurysms can happen anywhere in your body. If they rupture (break open), they may cause life-threatening internal bleeding.
• Arterial diseases. These include coronary artery disease, carotid artery disease and peripheral artery disease (PAD). These diseases make your arteries narrow, usually due to atherosclerosis.
• Atherosclerosis. This buildup of plaque (cholesterol, fat and other substances) inside your arteries can lead to a heart attack or stroke.
• Blood clots. Clumps of blood form inside veins or arteries. Clots block blood flow and can lead to deep vein thrombosis (DVT), pulmonary embolism, stroke or an artery blockage.
• High blood pressure (hypertension). This happens when there’s too much force against the walls of your arteries.
• Raynaud’s syndrome. This causes narrowing in arteries that supply blood to your skin. This happens in response to stress or cold temperatures.
• Varicose veins. Twisted and enlarged veins that usually form in your legs or feet
• Vascular malformations. Abnormal clusters or connections between blood vessels. Conditions like arteriovenous malformations are often congenital (present at birth).
• Vasculitis. Blood vessel inflammation. Blood vessel walls can thicken and narrow, which prevents blood from flowing freely.

Symptoms when something isn’t working right

Symptoms vary widely across the different types of blood vessel disorders. Some, like aneurysms or vascular malformations, may not cause symptoms until a serious problem develops.

In general, it’s a good idea to talk to a healthcare provider if you experience:

• Changes in skin color, like a bluish skin tone
• Coldness or numbness in your legs, feet, arms or hands
• Difficulty performing physical activities
• Fatigue
• Pain in your chest, belly, arms or legs
• Shortness of breath

Seek immediate medical attention if you experience:

• Confusion or difficulty speaking and understanding
• Sudden numbness or weakness on one side of your body
• Sudden vision loss
• Difficulty walking or balance problems
• Dizziness or fainting
• Fast heartbeat
• Severe pain in your chest, upper back, arms or legs
• Sudden or worsening shortness of breath
• Edema (swelling) in your arms or legs

Simple lifestyle changes to keep blood vessels healthy

There are a variety of ways you can improve the health of your blood vessels, including:

• Eat healthy foods that are low in sodium, cholesterol and saturated fats.
• Be physically active for at least 150 minutes a week.
• Manage your blood pressure, blood sugar and cholesterol levels.
• Avoid tobacco products.
• Reduce the amount of alcohol you drink.