1. The Circulatory System

2. The Basics
The main components of the circulatory system are the heart, blood vessels, and blood.
Together these components circulate blood through out the body.

3. Blood: Composition
Blood is a viscous, or sticky, fluid which flows inside the vessels of the circulatory system.
There is approximately 5.5 Litres of blood in the human body.

4. Blood: 3 Cell Types Blood is made up of blood plasma.
Within the blood plasma there are 3 types of of cells.
Red blood cells
White Blood Cells
Platelets

5. Blood: Red Blood Cells
Red blood cells are the most common type of blood cell.
They are disk shaped and have no nucleus.
They contain haemoglobin, the pigment that makes blood red and also transports oxygen.

6. Blood: White Blood Cells
There are fewer white blood cells than red blood cells in the body.
White blood cells help protect the body from infection, and eliminate cell debris.
There are also 5 different types.

7. Blood: Platelets Platelets are made up of cell fragments.
These cell fragments contain substances that allow the blood to clot.

8. Blood Types
The membranes of the red blood cells contain different proteins.
These proteins are responsible for creating the different blood types.
Type A
Type B
Type AB
Type O

9. Blood Vessels
Blood vessels allow for blood to circulate through out the body.
There are 3 types of blood vessels.
Arteries
Capillaries
Veins

10. Blood Vessels: Arteries
Arteries carry blood away from the heart.
The largest arteries are elastic.
As arteries get further from the heart they get smaller, these are called arterioles.

11. Blood Vessels: Capillaries
Capillaries are microscopic blood vessels that are found in every body tissue.
There are several million capillaries found in the circulatory system.

12. Blood Vessels: Veins When capillaries come together they form veins.
Veins are responsible for taking blood back to the heart.
Within veins there are valves that allow blood to flow to the heart, but not in the opposite direction.

13. The Heart
The heart is divided into four chambers: two atria and two ventricles.
Veins enter the atria while arteries leave from the ventricles.
Also, there is an atriovencular valve which allows blood to flow in one direction.

14. Heartbeat
The heartbeat is the movement of the heart which pumps blood.
It is made up of three phases
Atrial Systole
Ventricular Systole
Diastole.

15. Cardiac Cycle Phase 1 Atrial Systole occurs when: The atria contract
Blood is pumped through the ventricles
Blood travels through the open antriovencular valves

16. Cardiac Cycle Phase 2 Ventricular Systole occurs when
The ventricles contract
Sigmoid valves open
Blood flows out into the pulmonary artery and aorta
At the same time, valves in ventricles and aorta close.

17. Cardiac Cycle Phase 3 Diastole occurs when The heart relaxes
Blood is drawn from the venae cavae and pulmonary veins
The blood flows into the atria.