The circulatory system transports blood throughout the body using the heart and blood vessels. The heart pumps oxygen-rich blood received from the lungs through arteries and delivers it to tissues via capillaries, where oxygen and nutrients are exchanged. Deoxygenated blood returns to the heart through veins to repeat circulation. Blood contains plasma, red blood cells, white blood cells, and platelets that aid circulation and defense.

2. The Circulatory
System

3. The circulatory system
• The circulatory system delivers
blood to the body´s tissues
through a network of blood
vessels. The main organ of the
circulatory system is the heart,
which sends oxygen and nutrient
rich blood to all our cells.

4. Blood is made up of plasma, red blood cells,
white blood cells and cell fragments called
platelets.
• Research functions of
• Plasma:
• Red blood cells:
• White blood cells:
• Arteries:
• Veins:
• Capillaries:

5. Check them!
• Plasma is a yellowish liquid which is 90% water. It carries the nutrients and
waste products.
• Red blood cells give blood its colour. They carry oxygen and carbon dioxide.
• White blood cells fight infection. They surround and absorb germs which
enter the body.
• When the body is losing blood because of a cut in the skin, platelets join
together and help stop the bleeding.

6. Blood is transported through
three types of blood vessels
• Arteries carry blood from the heart to the rest
of the body. This blood contains oxygen.
• Veins carry the blood back to the heart. This
blood contains carbon dioxide.
• Capillaries are tiny blood vessels which
connect the arteries and the veins. They have
very thin walls so gases and nutrients can
easily pass through them to the cells.

7. The heart
• The heart is a hollow
muscle which pumps
blood through the body.
Research: what is the
average beats per minute?
When we do exercise,
does our heart beat faster
or slowly? Why?

8. Lebel the parts
of the heart
• Word bank:
• aorta, superior vena
cava, pulmonary
artery, left atrium,
pulmonary vein, right
atrium, right ventricle,
inferior vena cava, left
ventricle, tricuspid
valve, aortic valve

9. Check the
answers!

10. The heart is made up of four chambers
• The heart is made up of four chambers inside a thick
muscular wall. The top two chambers are called the
right and left atria; (atrium: singular, atria: plural) they
receive blood coming into the heart. The bottom part of
the heart is made up of the right and left ventricles. The
atria and the ventricles are separated by valves which
prevent blood from flowing backwards.

11. Circulation
• Blood flows around the body in a double circuit.
• During pulmonary circulation, blood flows from the
heart to the lungs and back to the heart again.
• During systemic circulation the blood flows from the
heart to the rest of the body.

12. Steps of the
Circulatory System
• 1.
• 2.
• 3.
• 4.
• 5.

13. Steps of the circulatory system
• 1. The deoxygenated blood passes from the right atrium of the heart to the
right ventricle. From there it leaves the heart via the pulmonary artery and
travels to the lungs.
• 2. In the lungs, blood releases carbon dioxide and collects oxygen. Blood
returns to the heart through the pulmonary veins.
• 3. The oxygenated blood flows into the left atrium and then into the left
ventricle. From there the blood is pumped through the biggest artery in the
body, called the aorta, to the rest of the body.

14. • 4. The aorta carries the blood into small arteries and then to the
capillaries. In the capillaries, the blood releases oxygen and nutrients
into the cells and collects carbon dioxide and other waste substances.
• 5. The deoxygenated blood passes from the capillaries to the small
veins and then to the largest veins in the body called the superior vena
cava and inferior vena cava. These veins carry the blood to the heart
and the process begins again.