8.3 Blood, Tissue Fluid and Lymph

Question 1

What are the components of blood?

Answer 1

Plasma 
Red blood cells 
White blood cells
Platelets 
Proteins 
Water 
Dissolved solutes

Question 2

What are the components of tissue fluid?

Answer 2

Water
Dissolved solutes
Very few white blood cells ( only enter tissue fluid if infection )
Very few proteins ( most too big to get through capillary walls )
No red blood cells ( too big )
No platelets ( only present if capillaries damaged )

Question 3

What are the components of lymph?

Answer 3

Water 
Dissolved solutes 
White blood cells 
Proteins ( but only antibodies ) 
No red blood cells 
No platelets

Question 4

What does blood transport?

Answer 4

Oxygen and carbon dioxide 
Digested food from the small intestine 
Nitrogenous waste products 
Hormones
Food molecules from storage compounds 
Platelets to damaged areas 
Cells and antibodies

Question 5

Apart from transport what are the other functions of blood?

Answer 5

Maintenance of steady body temperature

Buffer - minimises pH changes

Question 6

How do changes in pressure cause substances to move into and out of the capillaries?

Answer 6

Arterial end : greater hydrostatic pressure inside capillaries than in tissue fluid which causes net flow of fluid out of capillary to form tissue fluid.

As fluid leaves, hydrostatic pressure reduces in the capillaries so it is much lower at the end of the capillary bed that’s nearest the venules.

At venous end : water potential in capillaries is lower than in tissue fluid due to fluid loss and high oncotic pressure. This causes net flow of fluid back into capillary by osmosis.

Question 7

Define oncotic pressure

Answer 7

The tendency of water to move into the blood by osmosis. This is generated by plasma proteins.

Question 8

Define hydrostatic pressure

Answer 8

When blood is under pressure from the surge of blood that occurs every time the heart contracts

Question 9

How does the drainage system work using lymph?

Answer 9

The smallest lymph vessels are the lymph capillaries

Excess tissue fluid passed into lymph vessels. Once inside, it’s called lymph.

Valves in the lymph vessels stop the lymph going backwards.

Lymph gradually moves towards the main lymph vessels in the thorax. Here it is returned to the blood near the heart.