Tissue fluid

Question 1

What is tissue fluid?

Answer 1

Fluid that fills space between cells

Has same composition as plasma in blood but has no plasma proteins, RBCs, + other components

Question 2

What happens to plasma in the blood?

Answer 2

Its forced through gaps in capillary walls except for components that are too large

Diffusion takes place between blood + cells through tissue fluid

Question 3

What do the plasma proteins that remain in the capillary do?

Answer 3

Such as albumin, which has osmotic effect, lowers WP of blood compared to surrounding tissue fluid

Question 4

What is oncotic pressure?

Answer 4

Tendency of water to move into blood via osmosis, is about -3.3kPa

Plasma proteins give blood high solute conc, so lower WP

Question 5

What is hydrostatic pressure?

Answer 5

Where blood is still under pressure as it flows through arterioles into capillaries, from surge of blood that occurs every time heart contracts

Higher at arteriole end of capillary bed, lower at venous end

Question 6

What happens at arterial end of the capillary bed?

Answer 6

• Hydrostatic pressure greater than oncotic pressure
• Forces plasma out capillary, forming tissue fluid
• RBCs + large plasma proteins stay in capillary

Question 7

What happens at venous end of capillary bed?

Answer 7

• Hydrostatic pressure falls, oncotic pressure still -3.3kPa
• Oncotic pressure has greater influence
• Tissue fluid goes back into capillary by osmosis
• Blood returns to veins, 90% tissue fluid back in blood vessels