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Cardiovascular System
Next Generation: HS.LS1.2 MS.LS1.3 MS.LS1.3 NGSS

Cardiovascular System

Author: Sophia Tutorial
Description:

Understand the system of blood vessels.

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Tutorial
what's covered
This lesson will focus on the purpose and structure of the cardiovascular system by looking at the:
  1. Overview of the Cardiovascular System
  2. Types of Blood Vessels
    1. Arteries
    2. Arterioles
    3. Capillaries
    4. Venules
    5. Veins

1. Overview of Cardiovascular System

The purpose of the cardiovascular system (sometimes called the circulatory system) is to move blood throughout the body. Blood provides our tissues with oxygen and other necessary materials. It also aids in the removal of carbon dioxide.

The cardiovascular system is composed of:

  • The heart: A muscular pump that circulates blood throughout the body.
  • Blood vessels: Tubes that transport the blood that's pumped by the heart. There are five different types of blood vessels: Arteries, arterioles, capillaries, venules, and veins.
terms to know
Cardiovascular System
A body system composed of the heart and blood vessels that acts to transport blood throughout the body.
Heart
A muscular pump that pumps blood throughout the body.

Blood Vessels
Tubes that carry blood to and from the heart and body.

2. Types and Purpose of Blood Vessels

The five different types of blood vessels work together to transport the blood that is pumped by the heart. The diagram below shows how they are connected.

File:7342-Bloodvessel.png

2a. Arteries
When blood first leaves the heart, it travels through the arteries, which are large in diameter. An artery has a large diameter and is made up of several layers.

File:7338-Structure.png

The layers include:

  • A layer of connective tissue
  • A layer of smooth muscle
  • A layer of endothelium

Arteries can pump high-pressure blood from the heart. They also have stretchable walls, which offer little resistance to blood flow. Therefore, with 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 measure 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.
terms to know
Arteries
A large diameter blood vessel that carries blood away from the heart.
Endothelium
A single layer of cells that forms the lining of various body cavities, including blood vessels.

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

2b. Arterioles
Arteries then branch off into arterioles. Arterioles are similar to arteries in that they also carry blood away from the heart, but arterioles are smaller in diameter. They have a couple of different layers:

  • A layer of smooth muscle
  • A layer of endothelium

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.

Arterioles will eventually branch into capillaries, which are even smaller in diameter.

term to know

Arterioles
A smaller diameter blood vessel that carries blood away from the heart.

2c. Capillaries
Capillaries are the smallest blood vessel in our body and are where substances are allowed to diffuse from the blood into tissues. This can happen because they are made of a single, very thin layer of endothelium. 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.

File:7339-Capillary.png

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.

term to know

Capillaries
The smallest blood vessels that act as a zone of diffusion between blood and tissues.

2d. Venules
From there, capillaries will start to branch back into venules. Venules are larger in diameter than capillaries, but are still small and still allow for some substances to diffuse. They start the transport of blood back to the heart.

term to know

Venules
A small diameter blood vessel that returns blood to the heart.

2e. Veins
From here, blood moves into veins, which have a larger diameter than venules. The purpose of veins is to transfer blood back to the heart. They have low resistance, but a unique thing about veins compared to some of our other vessels is that they 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.

File:7340-Vein.png

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

EXAMPLE

An 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. Your blood pressure will rise, and then more blood will be delivered to your heart more quickly.

term to know

Veins
A large diameter blood vessel that returns blood to the heart.

summary
The cardiovascular system includes the heart and blood vessels. Its purpose is to circulate blood and nutrients throughout your body. There are five different types of blood vessels. Blood moves away from the heart through the arteries, then to the arterioles and into the capillaries. Here blood diffuses substances into and out of the bloodstream. Blood begins to return to the heart through venules, then into veins. Keep up the learning and have a great day!

Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

Attributions
  • Artery | Author: Wikipeda | License: Creative Commons
  • Blood Vessels | Author: Wikipeda | License: Public Domain
  • Capillary | Author: Wikipeda | License: Creative Commons
  • Vein | Author: Wikipeda | License: Creative Commons
Terms to Know
Arteries

A large diameter blood vessel that carries blood away from the heart.

Arterioles

A smaller diameter blood vessel that carries blood away from the heart.

Blood Vessels

Tubes that carry blood to and from the heart and body.

Capillaries

The smallest blood vessel that acts as a zone of diffusion between blood and tissues.

Cardiovascular System

A body system composed of the heart and blood vessels that acts to transport blood throughout the body.

Endothelium

A single layer of cells that forms the lining of various body cavities, including blood vessels.

Heart

A muscular pump that pumps blood throughout the body.

Pulse

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

Veins

A large diameter blood vessel that returns blood to the heart.

Venules

A small diameter blood vessel that returns blood to the heart.