4.6 tissue fluid

Question 1

4.6

How is tissue fluid formed?

Answer 1

• tissue fluid leaves the capillary though pores (at the arieriole end)
• because the hydrostatic pressure is greater than oncotic pressure
• plasma proteims are present in but but not in tissue fluid
• because they are too large to leave capillary

Question 2

What is oncotic pressure?

Answer 2

the pressure exerted by the proteins in the blood plasma that draws water into the blood vessels.

Question 3

1) What happens when hydrostatic pressure is higher than oncotic pressure?
2) What happens when oncotic pressure is higher than hydrostatic pressure?

Answer 3

1) Water moves out capillary into tissue fluid
2) Water moves back into capillary out of surrpunding tissue

Question 4

Explain how tissue fluid is returned to capillaries.
(3)

Answer 4

• there are more proteins in the plasma than in the tissue
• because they (plasma proteins) are too large to fit through pores in capillary
• (plasma proteins generate oncotic pressure)
• so oncotic pressure in the capillary is higher than hydrostatic pressure, causing water to move back in

Question 5

Explain why the production of tissue fluid is vital for cells in the human body.
(2)

Answer 5

• supplies tissues with oxygen/amino acids/glucose
• removes CO2 (waste product)
• allowing for respiration/growth/protein synthethesis
• pH controlled/cells not poisoned by toxic waste buildup

Question 6

Describe what happens to the tissue fluid that is not reabsorbed into the blood capillary.
(2)

Answer 6

• tissue fluid enters the lymphatic system/vessels
• lymph returns to the subclavian veins/blood

Question 7

What is the lymphatic system?

Answer 7

The lymphatic system is separate from the circulatory system. Lymph vessels of the lymphatic system begin in the tissues
lymph passes through the lymphatic system and drains back into the blood at the subclavian vein
lymph contains lymphocytes that produce antibodies which are emptied into the blood along with the lymph.
lymph glands also remove bacteria and other pathogens
hence the lymph glands swell when a person has an infection

Question 8

Lymphatic ducts remove proteins that are secreted by cells.
Explain how a blockage of a lymphatic duct could lead to swelling of body tissue (3)

Answer 8

• proteins would accumulate in the tissue fluid
• this would alter oncotic pressure
• meaning that water would not move back into the capillary