1. BLOOD

2. Blood volume is usually about 5 litres per person.
Blood is made of various types of different cells floating or bathed in a liquid-plasma.
Blood cells live for about 4 months
Blood has various functions….

3. Functions of Blood TRANSPORT. PROTECTION. REGULATION:
Carries nutrients/ dissolved food substances
Carries oxygen to cells
Removes carbon dioxide/ waste
Involved in carrying hormones and antibodies
Provides clotting factors when injured
Contains white blood cells to help fight disease
Regulates the amount of chemical substances in the tissues
Helps maintain body temperature
Controls the amount of fluid in the tissues

4. Components of Blood Red blood cells (main type - erythrocytes):
Round donut shape or disc shaped
The shape increases the surface area and they can take up more oxygen
NO Nucleus
Filled with haemoglobin (makes it look red)
White blood cells (leukocytes which fight infection)
No haemoglobin
DO have Nucleus
Form part of the immune system which kills unwanted microorganisms
Divided into 2 different types:
Phagocytes: engulf and eat invaders Lymphocytes: make antibodies to disease
Blood also contains platelets, involved in clotting

5. How does blood carry out some of the functions??
Carrying oxygen via haemoglobin:
A red respiratory pigment carried in the red blood cells
Contains iron – a lack of iron or low haemoglobin results in anaemia
Combines with oxygen to form oxyhaemoglobin

6. Functions cont… Removing carbon dioxide:
CO2 produced by cellular respiration ~ remember
Combines with water to form carbonic acid and therefore lowers blood pH
This means it can only be carried in small amounts
23% combines to form carbaminohaemoglobin, while the rest is transported in plasma as hydrogen carbonate ions.

7. NOTE
You may have heard of carbon monoxide, this is what is produced by the car exhaust – it is dangerous because it is taken up by the red blood cells quicker than oxygen (300x) as the haemoglobin thinks it is similar. It then means that the oxygen cant be taken up and we will die!
See pg and pg. 157

8. Blood cells are produced in bones – red marrow at the ends of the long bones, and in flat bones like ribs, skull and pelvis
Platelets are fragments of cells and are involved in preventing blood loss and clotting:
- Plasma proteins are also involved in clotting.
- Albumen makes the blood viscous and thick
- Globulin destroys the germs and is involved with the antibodies
- Fibrinogen clots the blood.

9. Blood Transfusions
People receive blood transfusions for various reasons
They sometimes involve just using plasma, not whole blood
Serum is plasma with the fibrinogen removed
A large loss of blood which may result in a transfusion being required is called a haemorrhage
The blood given must be compatible with the persons blood receiving the transfusion (same blood group)
If its not compatible the blood clumps together, forming clots and leads to death.

10. Haemorrhage
If someone haemorrhages the body goes into a clotting process:
The platelets come and make the wound sticky
Fibrinogen starts to be produced and then thrombin comes along to convert it to fibrin
Fibrin forms long sticky threads which attach to the leaky vessel wall and forms a web
This catches the red blood cells and forms the clot
NOTE: without clotting factors someone can bleed to death. Have you heard of haemophilia??