Blood & Circulation

1. Blood and circulation
Chapter 6

2. Topics to be covered
1. Components of the circulatory system
2. Composition of blood: Structure and function of the
components: RBCs, WBCs, platelets and plasma
3. Blood clotting
4. Structures and functions of blood vessels: Arteries,
veins, capillaries
5. Structure of the heart
6. Composition of tissue fluid
7. Heart diseases

3. The components of the circulatory system
The circulatory system is a closed system composed of three
components
● The vast network of tubes running throughout the body
consisting of veins arteries and capillaries
● A double pump which is the heart that pumps blood to the
rest of the body
● A fluid suspension known as blood

4. Composition of blood BLOOD
BLOOD CELLS PLASMA
WHITE BLOOD CELLS
OR LEUCOCYTES
PLATELETS
RED BLOOD CELLS OR
ERYTHROCYTES
PHAGOCYTESLorem Ipsum
CARRIES OXYGEN AND
CARBON DIOXIDE
LYMPHOCYTES

5. RED BLOOD CELLS (ERYTHROCYTES)
Main function: Carries oxygen and
Carbon dioxide
Structure Function
● Biconcave disc
shaped
● No nucleus or
mitochondria
● Contains
haemoglobin which is
part iron (haemin) and
part protein (globin)
● Large surface area, can
easily squeeze through
blood capillaries
● Has more space to carry
oxygen and carbon dioxide
● Haemoglobin temporarily
combines with oxygen to
form oxyhaemoglobin to
carry it around the body

6. White blood cells
White blood cells make up the first line of defence in the
body against diseases
There are two major types of White Blood cells
Lymphocytes
Phagocytes

7. White blood cells: Lymphocytes

8. White Blood Cells: Lymphocytes
Contains nucleus and other cel organelles
Produces antibodies which detect antigens (proteins on the
cell surface membrane)
Antibodies destroy antigens by
● Making them stick together
● Neutralizing toxins produced by them
● Dissolving them

9. Lymphocytes and antigens

10. Phagocytes
Amoebic in nature and movement
Destroys pathogens by attaching with them and then engulfing
them
Contains lysosomes filled with enzymes that break the
pathogens down

11. Phagocytes

12. Platelets and blood clotting
When there is a cut in a blood vessel the following things
happen
1. The blood constricts at that point to reduce blood flow
out of the cut. This only lasts a few minutes
2. Platelets (fragments of cells in the blood plasma) are
activated
3. They rush to the opening of the cut and stick to one
another, temporarily sealing the cut
4. Fibrinogen, a soluble protein is converted to fibrin

13. Clotting (continued)
5. Fibrin forms a network of threads which makes the blood
coagulate
6. The RBCs and other components get trapped in the network
of fibrin giving it its characterstic color
7 The fibrin dries, the trapped blood cells eventually die,
forming a scab

14. Blood vessels