1. The Circulatory System
Blood vessels

2. Each human being has approximately 5 litres of blood in his/her body
Each human being has approximately 5 litres of blood in his/her body. Each time the heart beats about 150 millilitres of blood is pumped out of it and carried to different parts of the body by means of blood vessels.

3. 3 different types of blood vessels
Arteries
Veins
Capillaries

4. Arteries and veins
The walls of the arteries and veins are made up of the same three layers
An outer fibrous connective tissue layer
A middle smooth muscle layer
An inner endothelium layer

6. Differences between arteries and veins
Carries blood away from the arteries
Carries blood towards the heart
Thick-walled because middle smooth muscle layer is thick
Thin-walled because middle smooth muscle is thinner
Blood is under pressure
Blood not under pressure
No valves within the arteries (except those within the heart)
Have semi-lunar valves to prevent back-flow of blood

8. The circulatory system
Blood circulation

9. Double circulation
Pulmonary circulation – Blood flows from the heart to the lungs and back to the heart.
Systemic circulation – Blood flows from the heart to all parts of the body and back to the heart.

11. Blood tissue Blood is salty Slightly sticky and reddish fluid.
pH of little more than 7
Composition of blood
55% is plasma
45% blood corpuscles

12. 3 types of blood corpuscles
Red blood cells (erythrocytes)
White blood cells (leucocytes)
Blood platelets

13. The main function is to transport oxygen.
erythrocytes
Disc-shaped
No nuclei
Haemoglobin – gives blood its red colour
Function
The main function is to transport oxygen.
The oxygen dissolves in the haemoglobin and forms oxyhaemoglobin before being transported

14. Leucocytes Irregularly shaped No nuclei Function
The leucocytes protects the body in the following ways:
They may engulf the microbes
They may form a barrier against the microbes
They may produce antibodies which destroy the microbes

15. The blood platelets play an important role in the clotting of blood
Fragments of cells
No nuclei
Function
The blood platelets play an important role in the clotting of blood

16. Blood plasma
Blood plasma acts as a transport medium for the following:
Digested food substances such as glucose and amino acid
Excretory products such as urea and uric acid
Plasma proteins such as fibrinogen which play an important part in the clotting of blood
Salts
Gasses such as oxygen and carbon dioxide
Hormones and enzymes

17. Functions of the blood system
It absorbs digested food from the alimentary canal and transports it to all parts of the body.
It absorbs oxygen in the lungs and transports it to all parts of the body.
It transports excretory wastes to the excretory organs (kidneys, lungs, and sweat glands in skin)