Tissue fluid

Question 1

How is tissue fluid formed?

Answer 1

• Capillaries have small gaps in the walls so that liquid and small molecules can be forced out.
• As blood enters the capillaries from arterioles, the smaller diameter results in a high hydrostatic pressure so water, glucose, amino acids, fatty acids, ions, and oxygen are forced out. This is known as ultrafiltration.

Question 2

What is forced out the capillary to form tissue fluid?

Answer 2

• Water
• Dissolved minerals and ions
• Oxygen
• Small proteins
• Fatty acids
• Glucose

Question 3

What remains in the capillary after tissue fluid is forced out?

Answer 3

• Red blood cells
• Platelets
• Large proteins

Question 4

How is water from tissue fluid reabsorbed?

Answer 4

The larger molecules left in the capillary lower the water potential so at the venule end of the capillary hydrostatic pressure is lowered and water potential is low. So, water re-enters by osmosis

Question 5

How does tissue fluid return into the blood?

Answer 5

Most of the tissue fluid is reabsorbed into the blood plasma because the hydrostatic pressure outside of the venule end of the capillary is higher than the inside and tissue fluid is forced back in.
Osmotic pressure (from proteins in the plasma) pull water back into the capillary

Question 6

What happens to the rest of the tissue fluid after most of it is reabsorbed?

Answer 6

It moves into the lymph vessels and drain back into veins near the heart