Blood, Tissue Fluid And Lymph

Question 1

What is oncotic pressure?

Answer 1

The tendency of water to move into the blood by osmosis (around -3.3 kPa).

Question 2

What causes the blood in the capillaries to have a high solute concentration (low water potential)?

Answer 2

The large plasma proteins

Question 3

Why is fluid forced out of the capillaries at the arterial end?

Answer 3

There is a high hydrostatic pressure from the surge of blood from the heart contracting (around 4.6 kPa), higher than the oncotic pressure attracting water in by osmosis.

Question 4

Why does the tissue fluid return to the capillaries at the venous end?

Answer 4

The hydrostatic pressure is now less than the oncotic pressure.

Question 5

What is lymph?

Answer 5

The 10% of tissue fluid which doesn’t return back into the capillaries and instead enters the lymphatic system

Question 6

What is lymph composed of?

Answer 6

It’s similar in composition to plasma and tissue fluid built has less oxygen and fewer nutrients, and contains fatty acids which have been absorbed by the lymph from the villi of the small intestine.

Question 7

What builds up in lymph nodes when necessary?

Answer 7

Lymphocytes (which produce antibodies which are then passed into the blood)

Question 8

What do lymph nodes do?

Answer 8

• Intercept bacteria and other debris from the lymph (then ingested by phagocytes)

• Produce antibodies (from the lymphocytes)

Question 9

What are the functions of the blood?

Answer 9

• Transport of oxygen, carbon dioxide, digested food, nitrogenous waste products, hormones, food molecules, platelets and antibodies

• Maintenance of body temperature

• Acts as a buffer to minimise pH changes