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Blood Vessels

Blood Vessels

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This lesson will classify the various types of blood vessels depending on their structure and function.

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Tutorial

What's Covered

This lesson will cover the structure and function of the different types of blood vessels by examining:

  1. Arteries
  2. Arterioles
  3. Capillaries
  4. Venules
  5. Veins


1. Arteries

Blood vessels are tubes that transport blood. They play an important role in our body, because they can help manage blood flow and blood pressure with the contraction or relaxation of the smooth muscles that surround them. These different types are responsible for carrying blood away from and returning it to the heart.

Term to Know

    • Blood Vessels
    • Tubes that transport blood throughout the body.

One of the types of blood vessels that carries blood away from our heart are arteries. An artery has a large diameter and is made up of several layers.

The layers include:

  • A Layer of connective tissue
  • Some smooth muscle
  • A Layer of endothelium

Term to Know

    • Arteries
    • Vessels of the largest diameter that carry blood away from the heart.

Arteries can pump high pressure blood from the heart, and they also have these stretchable walls, which offers little resistance to blood flow. Therefore, within arteries there's usually a stable pressure.

IN CONTEXT
Have you ever taken your pulse following a workout? What is this that you are feeling?

When you are measuring your pulse, you are actually measuring is the pressure surge in arteries when the ventricles within your heart contract. You can feel your pulse at different parts of your body, either on your wrist or by your carotid artery near your neck.

Term to Know

    • Pulse
    • The surge of pressure felt in an artery when ventricles of the heart contract.

2. Arterioles

Our next type of vessel that carries blood away from the heart is arterioles. Arterioles are the blood vessels that branch off from an artery. They have a smaller or narrower diameter and consist of a couple different layers, as well.

These layers include:

  • A Layer of smooth muscle
  • A layer of endothelium

Term to Know

    • Arterioles
    • Smaller vessels that branch from arteries that carry blood away from the heart.

Arterioles can dilate or constrict, also, because of that smooth muscle. Arterioles offer a little bit more resistance to blood flow than arteries because of their narrow diameter and ability to constrict or dilate quickly.


3. Capillaries

Capillaries are the vessels that branch off from arterioles. Capillaries are tiny vessels that are found in capillary beds, which is basically an interlacing network of capillaries. They are composed of just one thin layer of endothelium, allowing for substances to easily diffuse between blood and tissues. The majority of diffusion between blood and tissue happens here. Blood moves very slowly in capillaries, and, because of the amount of capillaries in our body, they offer less resistance to blood flow than arterioles.

Term to Know

    • Capillaries
    • The smallest vessels that act as zones of diffusion between blood and tissues.

Think About It

What type of blood vessel do we have the most of in our body?

Compared to any other vessel, we have the most capillaries. This is because capillaries are responsible for most of the diffusion that occurs between our blood and all of the tissues throughout our body.


4. Venules

Capillaries will start to move blood back into venules, and venules start to return blood back to the heart. Venules also have thin walls, and, because of the thin walls, some substances can still continue to diffuse across in venules.

Term to Know

    • Venules
    • Small vessels that merge with capillaries to carry blood back to the heart.

5. Veins

Veins have a larger diameter than venules. They have low resistance, but a unique thing about veins compared to some of our other vessels is tthey have valves. Because blood traveling in veins is going against gravity, veins have valves that prevent backflow creating a one-way system of flow back to the heart.

Term to Know

    • Veins
    • Large diameter vessels that return blood back to the heart and contain valves to prevent backflow of blood.

bloodvessel.png

This is a diagram of a vein. The layers of a vein include:

  • A layer of connective tissue
  • Smooth muscle
  • Endothelium

The contraction of the smooth muscle equals stiffer walls of the vein, which equals a rise in pressure, which, in turn, equals more blood flow to the heart.

ExampleAn example of how this works and its importance can be seen when you exercise. Those smooth muscles will contract, and then that will cause the walls of the blood vessels to stiffen. Blood pressure will rise, and then more blood will be delivered to your heart more quickly.

Summary

heart.png

There are several different types of blood vessels in the human body responsible for carrying blood away from and returning it to the heart. Blood leaves the heart through arteries which are large in diameter. Arteries then branch into arterioles. Arterioles branch into capillaries which act as an area of diffusion. Venules will begin the return of blood to the heart, while still allowing for some diffusion. Venules then merge into veins, which are larger in diameter, and finish the job of returning blood to the heart.

Keep up the learning and have a great day!

Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Pulse

    The surge of pressure felt in an artery when ventricles of the heart contract.

  • Veins

    Large diameter vessels that return blood back to the heart and contain valves to prevent backflow of blood.

  • Venules

    Small vessels that merge with capillaries to carry blood back to the heart.

  • Capillaries

    The smallest vessels that act as zones of diffusion between blood and tissues.

  • Arterioles

    Smaller vessels that branch from arteries that carry blood away from the heart.

  • Arteries

    Vessels of the largest diameter that carry blood away from the heart.

  • Blood Vessels

    Tubes that transport blood throughout the body.