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What is the Difference Between Arteries, Veins, Blood Vessels and Capillaries?
Arteries, veins, and capillaries are in fact all forms of blood vessels, just with different shapes and roles in the body. Blood vessels are an integral part of the circulatory system, which transfers oxygen and important components of life around the body and removes waste. Each of the three major types of blood vessels play their own role in this complex system, helping to keep a human body functioning at full strength and health.
The arteries are those blood vessels that carry blood away from the heart. This means that, with only two exceptions, arteries are carrying highly oxygenated blood to transport oxygen to the tissue of the body. Arteries are the higher-pressure part of the circulatory system, as they are getting blood from the heart. The pressure in the arteries differs between when the heart contracts and when it expands, the systolic and diastolic pressure, respectively. It is this pressure shift that can be felt as a pulse.
The largest artery in the body is the aorta, in the heart. The aorta receives blood from the heart’s left ventricle, then branches off into smaller and smaller arteries, eventually turning into arterioles, which supply the capillaries with blood. Pulmonary arteries are another special type of artery, which carry deoxygenated blood from the heart to the lungs, when they can be replenished, disposing of their carbon monoxide and gathering oxygen.
Veins are those blood vessels that carry blood back to the heart, with a few minor exceptions. For the most part, veins are carrying deoxygenated blood back to the heart, although this is not the case in either pulmonary or umbilical veins, where they carry oxygenated blood. Veins are basically tubes that just collapse when not filled with blood. Within veins are flaps that keep the blood flowing towards the heart, rather than being pulled down and pooling by the effects of gravity.
The blood carried by veins, in addition to having little oxygen, is also filled with carbon dioxide and various forms of cellular waste. Blood moves through the veins back to the heart, where it enters in the right ventricle, where it is then pumped into the lungs by the pulmonary artery, and then back through the heart via the left atrium.
Both veins and arteries are most easily defined not by the oxygen content of the blood, which is generally high for arteries and low for veins, but not always, but rather by the direction of blood flow. Arteries are always moving blood away from the heart, while veins are always moving blood towards the heart. Capillaries, on the other hand, act as intermediaries, connecting arterioles and venules.
Capillaries serve the function in the circulatory system of helping to facilitate the exchange of various things between blood and tissue. When the arteries bring blood to an area of tissue, they pump the blood into the capillaries, which can then essentially drop off the oxygen, water, and nutrients. The tissue can then dispose of its cellular waste and carbon dioxide, which the capillaries then pump back into the veins to be returned to the heart and lungs.
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![A diagram of the aorta, the largest artery in the body.]()
By: bilderzwergA diagram of the aorta, the largest artery in the body. -
![A diagram showing the composition of a blood vessel.]()
By: Balint RaduA diagram showing the composition of a blood vessel. -
![A diagram of the human head and neck, including the arteries in red.]()
By: AlilaA diagram of the human head and neck, including the arteries in red. -
![The arteries and veins in the hand evolved to carry blood to the tips of each finger.]()
By: London_EnglandThe arteries and veins in the hand evolved to carry blood to the tips of each finger. -
![Arteries have a higher blood pressure than veins.]()
By: niyazzArteries have a higher blood pressure than veins. -
![Capillaries connect the arterioles and the venules.]()
By: blueringmediaCapillaries connect the arterioles and the venules.
Discussion Comments
@Ana1234 - Losing a lot of blood at once is just generally bad for you as well. It can make you quite sick to lose it quickly, even if it's not the same quantity that you have lost with a vein being cut.
When I was giving blood once, the nurse put the needle into an artery instead of a vein and the blood was all pumped out in the space of about a minute. I felt very sick afterwards and had to rest for about half an hour because I couldn't stand without falling over. It was the same amount of blood, but since it left my body so fast through an artery rather than a vein, it caused a lot more problems than I usually have.
In a practical sense, it's good to know the difference between these blood vessels if you ever get cut or otherwise wounded. If the blood is just oozing out slowly then you don't have to worry too much (unless you have a clotting disorder) because you've probably just damaged some capillaries and they heal quickly.
If the blood is flowing out fairly slowly an steadily, then you've probably cut a vein which isn't that dangerous but if it's a big cut of course you want to get stitches and everything.
If, however, the cut is pumping out blood at regular intervals, you've probably cut an artery. This can be very dangerous, especially if it's a large cut, so get assistance right away. It's much more difficult for the wound to clot when an artery is cut and the heart will continue pumping out blood even if you have lost too much of it.
Thanks for the info. --Mary C.
Though many people don't really think about it, keeping your arteries, veins, and the rest of your circulatory system healthy is so important for the rest of your health. It only takes a little buildup to block the blood flow to an area of your hearth, and when blood flow to an area of your heart muscle is completely blocked, one suffers from a heart attack. What happens is that the block prevents oxygen-rich blood from reaching that area of heart muscle and causes it to die.
I think that of all the things that can go wrong with your veins and arteries, coronary heart disease has got to be one of the scariest, partially because it's just so common.
What happens in coronary artery disease is that plaque builds up inside the coronary arteries. Plaque narrows the arteries and reduces blood flow to your heart muscle. It also makes it more likely that blood clots will form in your arteries which can partially or completely block blood flow.
It's really important to know the symptoms of coronary artery disease, since it is so common, especially in Western countries, so remember, symptoms of blocked arteries are chest pain or discomfort and pain in shoulders, arms, neck, jaw, or back.
If you are experiencing these symptoms together, you should contact your doctor or go to the ER at once -- better safe than sorry.
Arterioles are also the main regulators of blood flow and pressure. They are the most highly regulated blood vessels in the body and are constantly changing size to speed up or slow down the flow of blood.The more constricted arterioles are, the greater their resistance to blood flow and the higher the blood pressure. The dilation of arterioles reduces resistance to blood flow, reducing blood pressure.
Here's one way to remember the difference between veins, arteries and capillaries. Veins are like the roads that lead into a city (the heart). Arteries are like the roads going out of a city. And capillaries are the back roads or county roads that eventually connect with the veins and arteries.
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