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Explain the Adaptations 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.

 

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 which pass in 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 as the ventricles have contracted (squeezed).  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. 

The lumen is the hollow corridor that blood flows through. Arteries have a small lumen keeping the blood under high pressure.

 

Capillaries 

Arteries divide into smaller blood vessels.  The smallest blood vessels are 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 them do this. Capillaries have very thin walls - they are only one cell thick. This means that the substances can diffuse in and out very quickly.

 

Veins

 

Image of vein with valves

 

 

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.  Veins don't have thick, strong, elastic walls. 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. Veins have larger lumens than arteries because they are under less pressure and this enables the blood to flow more easily.

 

Gas Exchange

The lungs are 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 via the pulmonary vein and then pumped around your body via the aorta from the heart. Carbon dioxide is the waste gas produced by respiration. Carbon dioxide diffuses from cells into the bloodstream and is pumped to the lungs via the pulmonary artery to be exhaled. 

 

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, which allows 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 explain the adaptations of the organs of the circulatory system.

The image shows a section through the heart.

C is the left atrium.

 

Name the structures labelled A and B and their functions.

 

Image of the heart

 

 

A - Pulmonary Vein - Transports deoxygenated blood to the lungs

A - Aorta - Transports oxygenated blood to the body

B - Aorta - Transports oxygenated blood to the body

B - Pulmonary vein - Transports oxygenated blood from the lungs to the heart

The body contains three different types of blood vessels - veins, arteries and capillaries.

 

Study the table below to see which type of blood vessel is represented by X, Y and Z.

 

Feature  X  Y  Z
 Valves      ✔
 Elastic fibres in blood vessel walls   ✔     
 Large lumen        ✔
 Walls are one cell thick      ✔  
 VeinCapillaryArtery
X
Y
Z

The largest artery in the body is the aorta. 

 

Describe the features of the aorta.

 

Image of the aorta labelled on heart

 VeinCapillaryArtery
X
Y
Z

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

 

How are capillaries suited to their function? 

Column A

Column B

They are one cell thick
They can fit into small spaces
They are narrow
Gases can diffuse quickly through the capillary wa...

 

The vena cava is the largest vein in the body. It carries deoxygenated blood back to the heart.

 

How are veins like the vena cava suited to their function? 

 

Image of vein with valves

Veins contain valves which prevent the back flow of blood

Veins have thick muscular walls

Veins are only one cell thick

 

The lungs can be seen in the image below.

 

Explain how the different structures help the lungs to function.

 

Image of the human lungs

Column A

Column B

Trachea
Allow gases to be exchanged very quickly into and ...
Bronchus and Bronchioles
Directs gases into and out of lungs
Alveoli
Allow gas to move quickly throughout the lungs

Breathing involves the exchange of gases in the lungs -  a process that occurs by diffusion.

 

What happens when you breathe in? 

Column A

Column B

Oxygen in inhaled air diffuses through...
... throughout the body
The oxygen is then transported...
...the alveoli in the lungs and into the bloodstre...
Carbon dioxide is the waste gas...
...produced by respiration
Carbon dioxide diffuses from body tissues ...
...into the bloodstream and is exhaled via the lun...

Alveoli have several adaptations. 

 

Explain how these adaptations help to make gas exchange very efficient.

 

Image of gas exchange in alveolus

Column A

Column B

Oxygen in inhaled air diffuses through...
... throughout the body
The oxygen is then transported...
...the alveoli in the lungs and into the bloodstre...
Carbon dioxide is the waste gas...
...produced by respiration
Carbon dioxide diffuses from body tissues ...
...into the bloodstream and is exhaled via the lun...

Arteries have layers of muscle in their walls.

 

Why's this important? 

Allows arteries to carry blood to the heart at low pressure

Allows arteries to carry blood away from the heart at high pressure

Allows arteries to carry blood to the lungs

Using the image below to help you, complete the steps describing how blood flows through the heart.

The first one has been done for you:

 

Number 1 -  Deoxygenated blood enters the right atrium from the vena cava. 

 

Image of the circulatory system

 

  • Question 1

The image shows a section through the heart.

C is the left atrium.

 

Name the structures labelled A and B and their functions.

 

Image of the heart

 

 

CORRECT ANSWER
A - Aorta - Transports oxygenated blood to the body
B - Pulmonary vein - Transports oxygenated blood from the lungs to the heart
EDDIE SAYS
How was this for a challenging start?! The aorta (labelled A in the image) is a massive artery and carries oxygenated blood from the heart to the rest of the body. The pulmonary vein (labelled B) carries oxygenated blood from the lungs to the heart, ready to be pumped by the heart via the aorta. This is the only example of a vein carrying oxygenated blood. The key to understanding the double circulatory system is to remember that arteries always carry blood away from the heart and veins always carry blood into the heart.
  • Question 2

The body contains three different types of blood vessels - veins, arteries and capillaries.

 

Study the table below to see which type of blood vessel is represented by X, Y and Z.

 

Feature  X  Y  Z
 Valves      ✔
 Elastic fibres in blood vessel walls   ✔     
 Large lumen        ✔
 Walls are one cell thick      ✔  
CORRECT ANSWER
 VeinCapillaryArtery
X
Y
Z
EDDIE SAYS
Did you get the idea of what to do here? Veins have Valves to prevent backflow, and a large lumen. This means that Z was the veins. Capillaries are very thin, only one cell thick, allowing quick gas exchange. This was Y. So X was the arteries, which have strong, elastic walls necessary for allowing the pressure of the blood travelling through them.
  • Question 3

The largest artery in the body is the aorta. 

 

Describe the features of the aorta.

 

Image of the aorta labelled on heart

CORRECT ANSWER
EDDIE SAYS
Remember: Arteries carry blood Away from the heart. The Aorta is one of the main Arteries. They all begin with the letter A!
  • Question 4

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

 

How are capillaries suited to their function? 

CORRECT ANSWER

Column A

Column B

They are one cell thick
Gases can diffuse quickly through...
They are narrow
They can fit into small spaces
EDDIE SAYS
Did you match these two OK? 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 5

 

The vena cava is the largest vein in the body. It carries deoxygenated blood back to the heart.

 

How are veins like the vena cava suited to their function? 

 

Image of vein with valves

CORRECT ANSWER
Veins contain valves which prevent the back flow of blood
EDDIE SAYS
Veins always carry blood into the heart - the word vein includes the word in! This means that they carry blood that is no longer under great pressure - in fact there might not be enough pressure to get the blood back to the heart without it flowing backwards. This is why veins need to have valves. Try to remember: Veins contain Valves!
  • Question 6
 

The lungs can be seen in the image below.

 

Explain how the different structures help the lungs to function.

 

Image of the human lungs

CORRECT ANSWER

Column A

Column B

Trachea
Directs gases into and out of lun...
Bronchus and Bronchioles
Allow gas to move quickly through...
Alveoli
Allow gases to be exchanged very ...
EDDIE SAYS
The lungs have different structures that help them to do their job - which is gas exchange. The inhaled air travels down the trachea into the bronchus and through into the bronchioles. From there, it travels into the alveoli, which are tiny air sacs. The oxygen diffuses into the bloodstream from the alveoli, to be carried throughout the body. Carbon dioxide is returned to the lungs in the bloodstream and diffuses back into the alveoli to be breathed out through the bronichioles, bronchus and trachea.
  • Question 7

Breathing involves the exchange of gases in the lungs -  a process that occurs by diffusion.

 

What happens when you breathe in? 

CORRECT ANSWER

Column A

Column B

Oxygen in inhaled air diffuses th...
...the alveoli in the lungs and i...
The oxygen is then transported...
... throughout the body
Carbon dioxide is the waste gas.....
...produced by respiration
Carbon dioxide diffuses from body...
...into the bloodstream and is ex...
EDDIE SAYS
Don't get your gases muddled up here! Oxygen diffuses out of the lungs into the bloodstream for all the cells of the body to use. Carbon dioxide is returned to the lungs in the bloodstream, and diffuses back through the alveoli to be removed from the body. Oxygen and carbon dioxide have the opposite pathways, so if you take the time to remember the pathway of one gas, the other gas should be easier to remember!
  • Question 8

Alveoli have several adaptations. 

 

Explain how these adaptations help to make gas exchange very efficient.

 

Image of gas exchange in alveolus

CORRECT ANSWER
EDDIE SAYS
Our bodies are really amazing, aren't they?! All this is going on without us being aware of it at all! Without these adaptations, gas exchange would be much slower and the body wouldn't be able to keep up its demands for respiration.
  • Question 9

Arteries have layers of muscle in their walls.

 

Why's this important? 

CORRECT ANSWER
Allows arteries to carry blood away from the heart at high pressure
EDDIE SAYS
Arteries have to transport blood around the body from the heart. The blood is high pressured, so the arteries need strong muscular walls to withstand this pressure. On the other hand, veins do not need such strong walls because they carry blood back to the heart under much less pressure.
  • Question 10

Using the image below to help you, complete the steps describing how blood flows through the heart.

The first one has been done for you:

 

Number 1 -  Deoxygenated blood enters the right atrium from the vena cava. 

 

Image of the circulatory system

 

CORRECT ANSWER
EDDIE SAYS
How did you get on with this one? Remember blood enters the atrium before entering the ventricle. The blood is then pumped out of the atrium (number 2), into the right ventricle (number 3). Then, the blood is pumped out of the heart through the pulmonary artery (number 4) which carries the deoxygenated blood to the lungs to have the carbon dioxide removed and to be replenished with oxygen. Well done - you've completed this activity - it was rather challenging!
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