1. Unit 2 Physiology and Health 2. Exchange of materials
Higher Human Biology
Unit 2 Physiology and Health
2. Exchange of materials

2. What do I remember?
The differences in structure of arteries, capillaries and veins
Direction of blood flow from and to the heart
What happens to blood pressure as blood moves away from the heart?
What is the role of vasoconstriction and vasodilation in controlling blood flow?

3. What you need to know What is tissue fluid?
How is tissue fluid different to plasma?
What is the purpose of tissue fluid?
What is the lymphatic system?
What is lymph?
Extra: what happens when the lymphatic system goes wrong?

4. What is tissue fluid? Blood: RBC’s, WBC’s, platelets
dissolved substances e.g.
glucose
amino acids
respiratory gases
plasma proteins
ions
All of the above are contained in plasma
Formation of tissue fluid
Blood from arteriole forced into much smaller capillary
Blood undergoes pressure filtration
Plasma squeezed out through capillary walls = tissue fluid

5. How is tissue fluid different to plasma?
Due to pressure filtration only the small molecules can pass through the capillary walls
Protein is too large to pass through
Protein stays in plasma
Tissue fluid therefore has no protein

6. Useful substances filtered out for use by cells Blood at low pressure
Blood at high pressure
Useful substances filtered out for use by cells
Blood at low pressure
Waste substances return to venule transported for excretion

7. What is the purpose of tissue fluid?
Tissue fluid enables he exchange of substances between blood and cells
Principles of osmosis and diffusion apply
Useful substances are pressure filtered out of the blood in order to diffuse into cells for use
Waste substances inc. Carbon dioxide diffuse out of cells into tissue fluid and returned to blood on venule side where blood pressure is low
Most tissue fluid returns to the blood by osmosis

8. What is the lymphatic system?
Part of the circulatory system
Series of vessels and nodes
Transports lymph (remaining tissue fluid)
Vessels need valves
Lymph transported by movement
Lymph returned to blood stream via ducts under the arms

10. What happens when the lymphatic system goes wrong?
Kwashiorkor
Protein deficiency
Prevents osmotic return of tissue fluid
Elephantiasis
Caused by worm in lymph vessel

11. What do I know? What is tissue fluid?
How is tissue fluid different to plasma?
What is the purpose of tissue fluid?
What is the lymphatic system?
What is lymph?
Extra: what happens when the lymphatic system goes wrong?