Circulatory System

What is the circulatory system?

Your body’s circulatory system consists of your heart and blood vessels. They use blood to bring your cells what they need and take away what they don’t.

Your heart pumps blood through the far-reaching, intricate network of arteries and veins. Your blood delivers oxygen and nutrients to your body’s muscles, tissues and organs. This network also removes waste and takes it to organs that can get rid of it.

People often refer to the circulatory system as the cardiovascular system. They are different names for the same system.

What is the circulatory system’s function?

Your circulatory system’s three basic functions are:

• Move blood throughout your body.
• Bring oxygen and nutrients to your organs, muscles and tissues.
• Remove waste products like carbon dioxide and your organs’ chemical byproducts.

Day and night, even while you’re asleep, your heart moves blood through your body in a circuit. If you follow the blood through your body, it moves from your heart into big highways for blood called arteries that deliver blood to your organs and tissues.

In your tissues, blood oxygen is exchanged for waste in tiny networks of blood vessels called capillaries. After leaving the tissues and organs, your blood returns to your heart through veins. The blood travels through your heart and lungs to get oxygenated again and repeat the process. This happens thousands of times each day, with every beat of your heart.

Your heart circulates about 2,000 gallons (more than 7,500 liters) of your blood every day. During physical activity, your heart pumps even more than usual. Your circulatory system adapts to meet your body’s needs for blood and oxygen.

Your circulatory system makes it a high priority to supply blood to your heart and brain. If your brain doesn’t get the blood it needs, you can lose consciousness within seconds. You can have brain damage after four minutes without blood flow. Similarly, your heart quickly starts to have trouble pumping if it’s not getting enough blood.

How your circulatory and cardiovascular system works

Your cardiovascular system functions with the help of blood vessels. Some blood vessels (veins) return blood to your heart, while others (arteries) carry blood away from your heart.

Your blood vessels work with your heart and lungs to continuously move blood through your body. Here’s how:

1. Your heart’s right ventricle sends blood that’s low in oxygen (oxygen-poor blood) to your lungs. Blood travels through the pulmonary trunk (the main pulmonary artery).
2. Your blood picks up oxygen in your lungs.
3. Pulmonary veins carry the oxygenated blood from your lungs to your heart’s left atrium.
4. The left atrium sends the oxygenated blood into the left ventricle. This muscular part of your heart pumps blood out to your body through arteries.
5. As blood moves through your body and organs, it drops off nutrients, transfers hormones and hauls away waste products.
6. The veins carry deoxygenated blood and carbon dioxide back to your heart, which sends the blood to your lungs.
7. Your lungs exchange oxygen for carbon dioxide, which you then exhale.

When blood gets oxygen from your lungs and brings it back to your heart, that’s your pulmonary circulation. Systemic circulation describes supplying oxygen-rich blood to your whole body.

Where is it located?

Your heart is located in the middle of your chest. It connects to your blood vessels, which go everywhere throughout your body.

What are the parts the circulatory system is made of?

Your heart and blood vessels make up your circulatory system. Each of these plays a role in moving blood through your body. This brings your cells oxygen and nutrients and removes waste.

What are the four main parts of the circulatory system?

The parts of your circulatory system are your:

• Heart. This muscular organ pumps blood throughout your body. Your heart is the only circulatory system organ. Your lungs are part of your respiratory system.
• Arteries. These thin, muscular tubes carry oxygenated blood away from your heart and to every part of your body. The aorta is your body’s largest artery. The coronary arteries branch off the aorta, which then branch into smaller arteries (arterioles) as they get farther from your heart.
• Veins. These blood vessels return oxygen-depleted blood to your heart. Veins start small (venules) and get larger as they approach your heart. Two central veins (the superior vena cava and inferior vena cava) deliver blood to your heart. Veins in your legs have valves to keep blood from flowing backward.
• Capillaries. These blood vessels connect very small arteries (arterioles) and veins (venules). Capillaries have thin walls that allow oxygen, carbon dioxide, nutrients and waste products to pass into and out of cells.

What does the circulatory system look like?

You can think of your heart as a hub that pumps your body’s blood. It connects to a network of blood vessels all over your body.

If you’ve ever seen water or sewer pipes under the street, you know they are very large. These pipes lead to smaller and smaller pipes that carry water into your house and sewage out of your house. Like the main pipes under the street, the blood vessels going into and out of your heart are the largest in your body. They connect to smaller and smaller blood vessels as they get farther away from your heart to deliver oxygen and remove waste throughout your entire body.

Blood vessels contain layers of connective tissue, muscle and elastic fibers. Muscles in your blood vessels control how wide they get, which also affects your blood pressure. Vasodilation makes your blood vessels wider and lowers your blood pressure. Vasoconstriction tightens your blood vessels, raising your blood pressure.

Your heart has muscle and other tissue. Blood flows through its four hollow chambers.

How big is the circulatory system?

Your heart is about the size of your fist but may be bigger if you have a heart condition. Your blood vessels run throughout your body from top to bottom, so the network is as tall and wide as you. Your body has more than 60,000 miles of blood vessels.

How much does your heart weigh?

Sex and overall body weight, as well as diseases, can affect your heart’s weight. But it’s about 8 ounces to 12 ounces.

What are the common conditions and disorders that affect the circulatory system?

Many of the problems with the parts of the circulatory system have to do with slowdowns or blockages in the blood vessels. As your blood vessels supply your entire body with oxygen, a blockage in any of the blood vessels makes it harder to deliver that oxygen.

Common circulatory system issues include:

• High blood pressure.
• High cholesterol.
• Arrhythmia (abnormal heart rhythm).
• Heart attack.
• Heart valves that don’t work right.
• Heart failure (weakness in your heart muscle).
• Aneurysm, most commonly in your aorta or brain.
• Stroke.
• Atherosclerosis (plaque buildup in your arteries).
• Heart disease.
• Vascular diseases (diseases involving blood vessels, like deep vein thrombosis and pulmonary embolism).

Simple lifestyle changes/tips to keep your circulatory system healthy

You can help keep your heart and blood vessels healthy in many ways, including:

• Getting regular physical activity. Aim for at least 150 minutes every week.
• Getting the sleep you need every night.
• Managing high blood pressure.
• Managing high cholesterol.
• Avoiding tobacco products.
• Eating heart-healthy foods, like those high in fiber and low in saturated fats.
• Staying at a weight that’s healthy for you.
• Keeping your blood sugar at a normal level.
• Finding healthy ways to ease stress.

What is red blood and blue blood?

All blood is red. Hemoglobin, an iron-rich protein in red blood cells, gives blood its red color. Some people refer to blood that’s rich in oxygen as red blood.

Your veins carry oxygen-poor blood. Sometimes, people call this blue blood because your veins can look blue underneath the skin. The blood is actually red, but the low oxygen levels give veins a darker bluish hue.

Do arteries always carry oxygenated blood?

For the most part, yes. The exceptions are pulmonary arteries and veins. Pulmonary arteries carry deoxygenated blood to your lungs. Pulmonary veins return the oxygenated blood to your heart.