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.
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.
Traveling the veins is probably the roughest part of the trip. The pressure in the veins is higher than it is in the capillaries, but nowhere near the pressure in the arteries. This makes it harder to get the blood to flow naturally to the heart. To help with this process, the veins contain valves that hold blood in place to build up pressure and then propel blood forward. Moving our bodies around by contracting our muscles also helps to move the blood along the route of the veins.
The veins from different parts of the body join together to form the largest vein in the body, which is the vena cava. The upper portion of the vena cava is known as the superior vena cava, and the lower portion of the vena cava is known as the inferior vena cava. Blood from the upper portion of the body passes through the superior vena cava, and blood from the lower portion of the body passes through the inferior vena cava. This is the point where blood is dumped back into the heart.
This whole process is a closed loop where blood never leaves the blood vessels. The entire route from the heart, to the body, and back to the heart is known as systemic circulation.
In this lesson, we discussed that blood is a fluid tissue that contains cells and other substances needed in the body. You should know that it travels through a closed system of blood vessels. The route from the heart, to the body, and back to the heart is known as systemic circulation.
There are five types of blood vessels. Arteries are the largest blood vessels in the body and carry blood away from the heart. Veins are the second-largest blood vessels and carry blood to the heart. Smaller arteries that reduce blood pressure are the arterioles. The venules are smaller veins that join together to increase pressure. The capillaries are the smallest blood vessels with the lowest pressure that serve as the site of exchange over the organs.
The largest artery in the body is the aorta, and the largest vein in the body is the vena cava. The upper portion is known as the superior vena cava, and the lower portion is known as the inferior vena cava.
After you've reviewed this video lesson, you will be able to:
- Define blood
- Identify the five types of blood vessels
- Explain the systemic circulation of the blood in the body
- Discuss the functions of the aorta, superior vena cava and inferior vena cava