1. Blood and Tissue Fluid
explain the differences between blood, tissue fluid and lymph
describe how tissue fluid is formed from plasma;

2. Blood Blood is liquid held in our blood vessels It consists of:
Plasma: watery fluid containing dissolved oxygen, carbon dioxide, salt, glucose, fatty acids, amino acids, hormones and plasma proteins (proteins made in the liver)
Cells including red blood cells (erythrocytes) white blood cells (leucocytes) and platelets

3. Tissue Fluid
Similar to blood but does not contain most of the cells found in blood or any plasma proteins
Role is to transport oxygen and nutrients from the blood to the cells and to carry carbon dioxide and other wastes back to the blood

4. Task
Using Biology 1 p77-78, explain what tissue fluid is and how it is formed
Complete SAQ 9 & 10 on p78

5. How Tissue Fluid is Formed?
When blood is under high pressure in the artery before it enters the capillary, some blood fluid is pushed out of the capillaries though tiny gaps in the capillary wall, this is called tissue fluid.
The pressure that the blood is under due to the contraction of the heart is called hydrostatic pressure (a bit like fluid pushing up against the walls of a container)

6. What is in Tissue Fluid? Plasma with dissolved nutrients and oxygen
The red blood cells, platelets and most of the white blood cells remain in the blood, with the plasma proteins. These are too large to fit through the gaps in the capillary wall

7. What does tissue fluid do?
It surrounds the body cells, so exchange of gases and nutrients can occur across the cell membranes (plasma membranes)
This exchange occurs by diffusion and facilitated diffusion
Oxygen and nutrients (e.g. glucose) enter the cells, carbon dioxide and other wastes (e.g. urea) leave the cells

8. How does the fluid get back into the blood?
The tissue fluid itself has some hydrostatic pressure and is pushed up against the capillaries allowing it to re-enter
The blood and the tissue fluid both contain solutes (dissolved substances) making their water potential more negative
The blood’s water potential is usually more negative so water tends to move from the tissue fluid back into the blood by osmosis, down the water potential gradient

9. Water potential: the analogy
Imagine 3 people, all of whom have a bank account with an overdraft (which means they can borrow money from the bank and make their account negative)
Whom should give money to whom?
Bill (Student)
-$800
Jim (Computer Designer) $0
Shelly (Office Worker)
-$475

10. Water potential: the analogy
Imagine 3 people, all of whom have a bank account with an overdraft (which means they can borrow money from the bank and make their account negative)
Total = -$1275 /3
Bill (Student)
-$425
Jim (Computer Designer)
-$425
Shelly (Office Worker)
-$425

11. Arterial end Venous end Total Hydrostatic pressure = 4.3-1.1 = 3.2kPa
Effective blood pressure = = 1.2kPa
Inside capillary (arterial end) fluid moves out of capillary as tissue fluid
Total water potential = -3.3 – (-1.3) = -2kPa
Arterial end
High hydrostatic pressure in capillary
Tissue fluid has higher hydrostatic pressure
Tissue fluid has lower hydrostatic pressure
Hydrostatic pressure = 4.3
Water potential = -3.3
Lower hydrostatic pressure in capillary
Hydrostatic pressure = 1.1
Hydrostatic pressure = 1.1
Hydrostatic pressure = 1.6
Water potential = -1.3
Water potential = -3.3
Venous end
Water potential = -1.3
Total Hydrostatic pressure = = 0.5kPa
Effective blood pressure = = -1.5kPa
Inside capillary (venous end) fluid moves into capillary from tissue fluid
Total water potential = -3.3 – (-1.3) = -2kPa

12. Movement back into the blood stream
At the venous (vein) end of the capillary, the blood has lost its hydrostatic pressure. The combined effect of the hydrostatic pressure in the tissue fluid and the osmotic force of the plasma proteins is sufficient to move fluid back into the capillary.
It carries with it any dissolved waste substances, such as carbon dioxide, that have left the cells

13. Lymph Complete the following questions using Biology 1 p78
What determines the amount of fluid leaving the capillaries?
Explain why fluid flows out at the arterial end and in the venous end
What is tissue fluid?
What is lymph?
How does tissue fluid get into the lymphatic system?
What is oedema?

14. Feature
Blood
Tissue Fluid
Lymph
Cells
Some phagocytic white blood cells
Proteins
Some proteins
Fats
Some transported as lipoproteins
Some/none
More than in blood (absorbed from lacteals in intestine-villi)
Glucose
80-120mg per 100ml
More/less
Amino Acids
Oxygen
Carbon dioxide
Lot/little

15. Feature
Blood
Tissue Fluid
Lymph
Cells
Erythrocytes, leucocytes and platelets
Some phagocytic white blood cells
Lymphocytes
Proteins
Hormones and plasma proteins
Some hormones, proteins secreted by body cells
Some proteins
Fats
Some transported as lipoproteins
None
More than in blood (absorbed from lacteals in intestine-villi)
Glucose
80-120mg per 100ml
Less (absorbed by body cells)
Less
Amino Acids
More
Oxygen
Less (absorbed by body cells)
Carbon dioxide
Little
More (released by body cells

16. Carriage of Oxygen
describe the role of haemoglobin in carrying oxygen and carbon dioxide;
describe and explain the significance of the dissociation curves of adult oxyhaemoglobin at different carbon dioxide levels (the Bohr effect);
explain the significance of the different affinities of fetal haemoglobin and adult haemoglobin for oxygen.

17. Task
Using Biology 1 p80-84, produce a revision box for each of the following:
Haemoglobin dissociation curve
Carbon dioxide transport in the blood
The Bohr shift
Fetal Haemoglobin
You are limited to one piece of A3 paper- you will need to read the information, decide what is important, and include it in the box, highlighting key terms

18. Haemoglobin Dissociation Curve Carbon Dioxide Transport
The Bohr Shift
Fetal Haemoglobin