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How Blood Travels Throughout the Body

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  • 0:03 Blood
  • 1:10 Types of Blood Vessels
  • 2:12 The Route of Blood
  • 4:33 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

This lesson is going to cover the different blood vessels that carry blood throughout the body. The route and changes in blood pressure will also be discussed. A short quiz will follow.

Blood

You are awakened by pain in your chest that is moving down your arm. You know something is really wrong and dial 911. Upon arriving at the ER, the doctors realize you are having a heart attack. You have heard of this before, but what is really happening during a heart attack?

The muscle of the heart is the part that contracts and, like every other organ in our bodies, it needs blood in order to function properly. Blood is a fluid tissue that contains blood cells, nutrients, and other substances. It is responsible for getting any needed gases or substances to the organs of the body and removing any unneeded gases and substances from the organs of the body.

Any time blood isn't being supplied to the heart, it is being deprived of the nutrients and oxygen that it desperately needs, and this results in a heart attack. This occurrence isn't unique to the heart. All of our organs need blood to do what they are supposed to do. If the brain doesn't get the blood it needs, then a stroke may occur. Most of our other organs will simply shut down and stop doing anything if there isn't blood flowing to them. But, how does blood get to every part of the body that needs it?

Types of Blood Vessels

Think of our blood as a transportation system for the body. Every transportation system has to have routes on which to travel. Trains travel on railroad tracks, and cars take the highways and roads. Our blood travels in much the same manner.

Blood uses a closed system of blood vessels to get to every organ in the body. Blood vessels are hollow tubes through which blood can flow. Just like all highways and roads aren't the same, all blood vessels are also not the same.

There are five different types of blood vessels. Arteries are the largest and strongest blood vessels that carry blood away from the heart. Veins are the second-largest blood vessels and carry blood to the heart. Arterioles are smaller vessels that branch off from arteries to reduce blood pressure, while venules are smaller vessels that join together to make veins. The smallest blood vessels that serve as the sites of exchange are the capillaries. Let's take a closer look at how the system of blood vessels work.

The Route of Blood

We'll start from a familiar place - the heart. The heart contracts to pump blood into the aorta, which is the largest artery in the body. The aorta branches off to make the arteries that lead to other areas of the body. The heart contracts with so much force that the blood continues through the arteries and on to the organs of the body. This is the reason why our blood pressure is the highest in our arteries.

As the arteries get closer to the organs, they begin to narrow to reduce the blood pressure, and this is the point where they become arterioles. The blood passes through the arterioles and then reaches the point where the arterioles become capillaries. At this point, the pressure is greatly reduced to allow for the exchange of oxygen and carbon dioxide as well as nutrients and waste products.

Now that the blood has made its delivery, it needs to take the picked up items back to the heart and get another load for delivery. After passing through the capillaries, the blood flows into the venules. The venules collect only a certain amount of blood at a time in an effort to increase pressure for transportation to the heart. The venules then join together to make veins, which further increases the pressure.

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