1. Fluids of the circulatory system
name them
the fluid derived from blood plasma, that surrounds the cells in a tissue
the fluid held in the heart, arteries, veins and capillaries
the fluid held in the lymphatic system (lymph nodes and lacteals)
Tissue fluid
Blood/plasma
Lymph

2. Learning Objectives the formation of tissue fluid from plasma
To include reference to
hydrostatic pressure,
oncotic pressure
an explanation of the differences in the composition of blood, tissue fluid and lymph.

3. Tissue fluid
colourless fluid formed from blood plasma by pressure filtration through capillary walls
surrounds all the cells of the body
Allows exchanges between the blood and cells of eg oxygen, glucose, carbon dioxide
Tissue fluid contains:
Glucose
Amino acids
Fatty acids
Salts
Oxygen
So what does the tissue fluid take away?
Carbon dioxide
Other waste products
Supplies all of these to the tissues

4. Pressures at work Hydrostatic Pressure Oncotic Pressure (-3.3KPa)
Pushing fluid out
arterial end about 4.6KPa
Venous end about 2.3KPa
Oncotic Pressure (-3.3KPa)
Blood proteins pulling fluid back in

5. Fluid in or out of the capillary?
Both hydrostatic and oncotic pressure are found in the blood vessels and in the tissues. Their relative balance determines whether fluid enters or leaves the capillary
What effect could high blood pressure have on tissue fluid formation.

6. Net outflow? Net inflow? 1.2kPa -1.0kPa see p183
Arterial end: blood is under high pressure (hydrostatic pressure = 4.6kPa) due to contraction of heart muscle
tends to push fluid out of capillaries through tiny gaps in their walls
(red blood cells, most white blood cells, platelets and plasma proteins are too large to leave)
Venous end: blood has lost hydrostatic pressure it is now 2.3 kPa.
Osmotic pressure -3.3kPa exceeds hydrostatic pressure so this creates a pull which moves fluid back into capillary
Net outflow?
Net inflow?
1.2kPa
-1.0kPa
see p183

7. Lymph A milky liquid made up of excess tissue fluid
not all tissue fluid returns to capillaries about 10% drains away into lymphatic system
fatty substances
absorbed from intestines
3. Lymphocytes
produced in lymph nodes (swellings along lymphatic system which filter bacteria from lymph fluid).
phagocytes engulf and destroy bacteria.

8. Human Lymphatic System
Lymphatic system is made up of one way vessels resembling blood capillaries
Start at tissues, drain excess fluid into larger vessels
Rejoin blood system in chest cavity
Lymphatic System

9. Lymphatic problems
Oedema accumulation of tissue fluid can have several causes.
Elephantiasis caused by roundworm infection in the lymph nodes
Malnutrition
Kwashiorkor

10. Jan 2004
Jan 2002
Past paper questions

12. Pulling fluid into tissues with a force of 0.2kPa
Capillary
HP +SP (OP)
4.3kPa +-3.3kPa= 1.0kPa
Tissues
HP=SP (OP)
1.1kPa kPa = -0.2kPa
Pulling fluid into tissues with a force of 0.2kPa
Add this to the capillary outward force of 1.0kPa = 1.2kPa in total
Capillary
HP +SP (OP)
1.6kPa +-3.3kPa= -1.7kPa
Tissues
HP=SP (OP)
1.1kPa kPa = -0.2kPa
Pulling fluid into tissues with a force of 0.2kPa
Add this to the capillary inward pull of kPa = -1.5kPa in total

13. NOTE
You may not be expected to take the hydrostatic and oncotic effect of the tissues into account but you should be aware of it

15. Heart

16. Lymph is moved along the vessels in three ways:
Hydrostatic pressure.
Contraction of the body muscles.
Valves maintain one way flow

18. Tasks
Complete the comparison table for blood, tissue fluid and lymph