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Recall the Main Structures and Functions of the Circulatory System

In this worksheet, students will recall the main structures and functions of the circulatory system.

Worksheet Overview

QUESTION 1 of 10

Did you know that your heart beats about 100,000 times a day?! And that it sends about 2,000 gallons of blood around your body?! That’s around the same amount as 16,000 pints of milk!

The cells in our body need a good supply of oxygen and nutrients.  They also need to get rid of waste substances. Our blood carries out both of these functions. The circulatory system consists of blood vessels such as arteries, veins and capillaries and a pump called the heart

The systems in the body all work together. The gaseous exchange system, the digestive system and excretory system all interact with the circulatory system in order to keep us alive. For example, during digestion, food is broken down by the stomach and small intestine. Water and dissolved food molecules are absorbed into the blood in capillaries. The glucose from the food is used for respiration, as well as oxygen from the gaseous exchange system. Waste products are expelled from the body via the excretory system. 

 

Image of the circulatory system

 

 

Blood passes through the heart twice on every full circuit of the body. This is called a double circulatory system. A double circulatory system separates the blood with oxygen from the blood without oxygen. Blood with oxygen is called oxygenated blood. Blood without oxygen is called deoxygenated blood.

Each organ of the body is supplied with blood from its own artery.  This blood is oxygenated. Deoxygenated blood is taken away from organs by veins. 

When blood has been pumped out of the left ventricle of the heart, it begins to make its journey around the body in an artery called the aorta.  The blood is rich in oxygen. Oxygen is carried by red blood cells. The oxygen leaves the red blood cells as they pass through the capillaries.  Capillaries are the network of blood vessels that pass between the cells in the body. As blood leaves the capillaries, it enters veins. Veins return blood to the heart.

 

Arteries

When blood flows out of the heart, it enters the arteries. The blood is at very high pressure because it has been forced out of the heart by the contraction (or squeezing) of the ventricles. Arteries have very strong walls to be able to cope with the high pressure of the blood flowing through them.  The blood moves through the arteries with every heartbeat.  The thick muscular walls stretch and then bounce back into place because of the elastic fibres in the walls of arteries.

 

Capillaries

Arteries divide into smaller blood vessels called capillaries. The function of a capillary is to take nutrients and oxygen to cells and take waste products away. The structure of a capillary helps it do this - capillaries have very thin walls, they are only one cell thick, which means that the substances can diffuse in and out very quickly.

 

 

Veins

Capillaries eventually join up again and form veins.  By the time the blood gets to the veins, it is at a much lower pressure than it was in the arteries, so veins don't need to have thick, strong, elastic walls. Instead, veins have valves to stop the blood from flowing backwards. Arteries do not have valves because the force of the heartbeat keeps the blood moving.

 

Gas Exchange

The lungs are well adapted for gas exchange. Breathing involves exchanging gases in the lungs. 

 

Image of the human lungs

 

 

When you breathe in, oxygen in the inhaled air travels down your trachea which branches off into bronchi (one branch is called the bronchus). This further divides into bronchioles and, eventually, the oxygen diffuses through the tiny alveoli (air sacs) in your lungs into your bloodstream. The oxygen is transported to the heart in the pulmonary vein and then pumped around your body in the aorta from the heart. The oxygen is needed for respiration that occurs in your cells. Carbon dioxide is the waste gas produced by respiration. Carbon dioxide diffuses from cells into the bloodstream and is pumped to the lungs in the pulmonary artery, to be exhaled.

This goes to show how the circulatory system and gaseous exchange system work together!

 

Image of alveolus and gas exchange

 

 

The alveoli have a few adaptations that make gas exchange very efficient. They are only one cell thick, making them very thin, allowing gases to pass through easily and quickly. They also have a large surface area, allowing large amounts of gases to be exchanged with each breath.

 

In the following activity, you will recall the main structures and functions of the circulatory system.

Which side of the heart pumps oxygenated blood? 

 

Image of the human heart

Left-hand side

Right-hand side

Both sides

Look at the image of the heart.

 

Why do the ventricles of the heart have thicker walls than the atria? 

 

Image of the hearts atria and ventricles

 

Atria pump blood out of the heart so have thicker walls

Ventricles receive blood from the atria

Atria collect blood coming into the heart

Ventricles have to pump blood out of the heart so have thicker walls

The body contains three different types of blood vessels.

 

What are the names of these blood vessels?  

Artery

Neurone

Vein

Capillary

Insulin

Match the blood vessels with their descriptions below.

Column A

Column B

Arteries
Always carry blood back into the heart
Veins
Always take blood out of the heart

Capillaries have some special features that help them to do their job.

 

How are capillaries suited to their function?

They have a thick muscular wall

They are only one cell thick

They contain valves

Arteries usually carry oxygenated blood and veins usually carry deoxygenated blood. 

 

What are the only arteries and veins that don't follow this rule?

They have a thick muscular wall

They are only one cell thick

They contain valves

The image shows a section through the heart.

 

Name the structures labelled A, B and C on the image below.

 

Image of the heart

 ABC
Aorta
Pulmonary vein
Left atrium

How does the digestive system help with the process of respiration? 

The digestive system breaks down food which will release glucose into the blood

The digestive system releases oxygen into the blood

The glucose is combined with oxygen to carry out respiration, releasing energy

The glucose is combined with carbon dioxide to carry out respiration, releasing energy

What are the names of some of the systems that interact with the circulatory system? 

Digestive system

Gaseous exchange system

Skeletal system

Excretory system

The blood is transported in a double circulatory system.

 

What does this mean?

Blood passes through the heart twice in every full circuit of the body

Blood travels in two directions inside the blood vessels

Blood with oxygen is mixed with blood without oxygen to speed up the process

Blood with oxygen is separated from blood without oxygen

  • Question 1

Which side of the heart pumps oxygenated blood? 

 

Image of the human heart

CORRECT ANSWER
Left-hand side
EDDIE SAYS
Try not to get confused - you have to imagine the image of the heart as if it's inside your body. So, the right side on the paper is actually the left-hand side in real life! The heart pumps oxygenated blood out of the left ventricle to the rest of the body through the aorta.
  • Question 2

Look at the image of the heart.

 

Why do the ventricles of the heart have thicker walls than the atria? 

 

Image of the hearts atria and ventricles

 

CORRECT ANSWER
Ventricles receive blood from the atria
Ventricles have to pump blood out of the heart so have thicker walls
EDDIE SAYS
The thicker walls of the ventricles allow for a greater 'push,' forcing the blood out of the heart with greater pressure, so allowing it to reach all areas of the body.
  • Question 3

The body contains three different types of blood vessels.

 

What are the names of these blood vessels?  

CORRECT ANSWER
Artery
Vein
Capillary
EDDIE SAYS
Hopefully, this didn't trip you up. The three you needed were artery, vein and capillary. A neurone is another name for a nerve cell and insulin is a hormone involved in blood sugar regulation!
  • Question 4

Match the blood vessels with their descriptions below.

CORRECT ANSWER

Column A

Column B

Arteries
Always take blood out of the hear...
Veins
Always carry blood back into the ...
EDDIE SAYS
This is one of the most important facts to remember about the circulatory system! Arteries always carry blood away from the heart. The words both start with 'A' which might help you to remember this. Veins always carry blood back into the heart - the word vein contains the word 'in' which might be helpful as a reminder!
  • Question 5

Capillaries have some special features that help them to do their job.

 

How are capillaries suited to their function?

CORRECT ANSWER
They are only one cell thick
EDDIE SAYS
Did you spot that option one was describing arteries and option three was referring to veins? Capillaries are extremely thin - they're only one cell thick! This means that gases and nutrients can diffuse really quickly from the blood into cells. If the capillaries were thicker, it would take longer for gases and nutrients to be exchanged and the blood wouldn't be able to meet the demands of the body.
  • Question 6

Arteries usually carry oxygenated blood and veins usually carry deoxygenated blood. 

 

What are the only arteries and veins that don't follow this rule?

CORRECT ANSWER
EDDIE SAYS
This is another key fact to remember! Arteries always carry oxygenated blood to the cells of the body with one exception - the pulmonary artery carries deoxygenated blood from the heart to the lungs. The only vein that carries oxygenated blood is the pulmonary vein, which supplies the heart with oxygen from the lungs.
  • Question 7

The image shows a section through the heart.

 

Name the structures labelled A, B and C on the image below.

 

Image of the heart

CORRECT ANSWER
 ABC
Aorta
Pulmonary vein
Left atrium
EDDIE SAYS
The pulmonary vein carries oxygenated blood from the lungs to the heart, ready to be pumped by the heart through the aorta. The aorta is an artery and carries oxygenated blood to the rest of the body. The left atrium is where the oxygenated blood enters from the lungs. Well done for completing a challenging activity!
  • Question 8

How does the digestive system help with the process of respiration? 

CORRECT ANSWER
The digestive system breaks down food which will release glucose into the blood
The glucose is combined with oxygen to carry out respiration, releasing energy
EDDIE SAYS
Did you wonder why this question appeared in an activity to do with the circulatory system?! This is because the circulation of the blood is essential for the transporting of dissolved food to different cells of the body! Respiration requires both oxygen and glucose. Oxygen is carried by the blood from the lungs to the cells of the body. Glucose is also carried in the blood, but from the small intestines to the body cells. Without the circulatory system, neither of these substances could be transported around the body!
  • Question 9

What are the names of some of the systems that interact with the circulatory system? 

CORRECT ANSWER
Digestive system
Gaseous exchange system
Excretory system
EDDIE SAYS
Our bodies are extraordinary organisms that are kept alive by the continuous activity of many different processes! There were three different systems listed above that need the circulatory system to transport essential substances around the body. These substances are needed for different processes such as respiration.
  • Question 10

The blood is transported in a double circulatory system.

 

What does this mean?

CORRECT ANSWER
Blood passes through the heart twice in every full circuit of the body
Blood with oxygen is separated from blood without oxygen
EDDIE SAYS
How did you get on with this question - it is fairly crucial to understand about the movement of the blood. In a double circulatory system, blood travels around the body twice in every full circuit. The first circuit takes deoxygenated blood from the heart to the lungs (in the pulmonary artery), picks up oxygen from the lungs and returns oxygenated blood to the heart (in the pulmonary vein). In the second circuit, the heart pumps oxygenated blood from the heart to the body's cells (in the aorta), delivers oxygen, glucose etc to the cells and returns deoxygenated blood to the heart in the vena cava. Simple!!
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