Name:
Unit:
Staying alive
The Human
Circulatory System
The Heart and the Circulatory System:
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.
Tasks:
1. Label this diagram of the
heart using the structures
in the table below:
2. Colour in the right atrium,
right ventricle, and
pulmonary artery with a
blue colouring pencil.
3. Colour in the left atrium,
left ventricle, and
pulmonary vein with a red
colouring pencil.
4. Show the direction of blood
flow through the heart
using arrows.
Right ventricle
Left ventricle
Pulmonary artery
Pulmonary vein
Aorta
Left Atrium
Right Atrium
Valves
Which side of the heart contains oxygenated blood? __________________________________
Which parts of the heart receive blood from the lungs? ________________________________
Which part of the heart receives blood from the rest of the body? ________________________
Which parts of the heart pump blood into the ventricles? _____________________________
Why do the ventricles have thicker walls than the atria?________________________________
____________________________________________________________________________
Why does the left ventricle have thicker walls than the right ventricle?_____________________
____________________________________________________________________________
Blood circulation around the body:
In this section you’ll learn about the flow
of blood around the body. This will
include how many times blood passes
through the heart as it is transported
around the body.
A double circulation:

Blood passes through the heart
twice on every full circuit of the
body.
o 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.

The pulmonary circuit pumps blood to the lungs.

The systemic circuit pumps blood to the body systems (i.e. the head, limbs, and trunk).
Each organ has its own blood supply:

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.
Questions about the circulatory system
What is a double circulatory system?
______________________________________________________________________________
______________________________________________________________________________
What is oxygenated blood? ______________________________________________________
Where do red blood cells pick up oxygen? __________________________________________
Blood vessels:
In this section you’ll learn about the different blood vessels that carry blood around the body.
Where does the blood flow?
When blood has been pumped out 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.
Task:
1. On this picture colour in
the arteries in red and
the veins in blue.
2. Then colour in the
capillaries on the artery
side in red and those
on vein side in blue.
Questions on blood vessels:
Which blood vessels carry blood away from the heart?
_______________________________
Which blood vessels carry blood towards the heart?
_________________________________
Arteries:
When blood flows out the heart, it enters the arteries. The blood is at very high pressure,
because it has been forced out of the heart because 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 in pulses, with every
heartbeat. The thick muscular walls stretch and then flex back into place because of the
elastic fibres in the walls of arteries.
Capillaries
Arteries divide into smaller and smaller blood vessels. The smallest blood vessels are called
capillaries. The capillaries are very small and penetrate every part of the body. A body cell is
never very far away from a capillary.
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, this
means that the substances can get 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. We can see this in the structure of veins.
Veins do not 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 heart beat keeps the blood
moving.
Task:
Using the information in the last three paragraphs, complete this summary table
What is their
What is the
How does their structure help
job?
structure of the
them do their job?
wall
Arteries
Capillaries
Veins
Questions:
Why do arteries have elastic walls? _______________________________________________
____________________________________________________________________________
____________________________________________________________________________
What is the function of capillaries?
________________________________________________
____________________________________________________________________________
____________________________________________________________________________
How is blood kept moving in the large veins of the legs? _______________________________
____________________________________________________________________________
____________________________________________________________________________
Why do arteries have strong walls?
____________________________________________________________________________
____________________________________________________________________________
The heart has its own blood supply.
Just like the other organs in body, the heart also has its own blood supply. This may seem odd,
especially when the heart has so much blood passing through it. The reasons that the heart has
its own supply is because it needs a lot of oxygen and nutrients to keep it working at its best
and also because the walls of the heart are so thick that oxygen and nutrients cannot easily
pass into where it is needed. The artery that supplies the heart with blood is called the
coronary artery.
If the coronary artery
gets blocked, then the
cells in the heart may run
short of oxygen. If this
happens then they will
not be able to contract
(squeeze). This is called
a cardiac arrest or
heart attack.
Questions:
What is the coronary artery?
_____________________________________________________
____________________________________________________________________________
____________________________________________________________________________
Why does the heart need its own blood supply?
______________________________________
____________________________________________________________________________
____________________________________________________________________________
Extended answer question:
Describe the movement of blood around the body stating at the right atrium.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
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