Tissue fluid and the lymph systemEdexcel A-Level Biology B: Subtopic test

1. 1
   In a capillary bed, the hydrostatic pressure of the blood is 4.0 kPa at the arteriole end and 1.5 kPa at the venule end. Throughout the capillary, the oncotic pressure of the blood plasma is 3.3 kPa. The hydrostatic pressure and oncotic pressure of the tissue fluid outside the capillary can be ignored.

   (a)

   What is the net pressure forcing fluid out of the capillary at the arteriole end?

   [1 mark]

   • A7.3 kPa
   • B4.0 kPa
   • C3.3 kPa
   • D0.7 kPa

   (b)

   What is the net movement of fluid at the venule end of the capillary?

   [1 mark]

   • AOut of the capillary, with a net pressure of 1.8 kPa
   • BInto the capillary, with a net pressure of 1.8 kPa
   • CThere is no net movement of fluid
   • DInto the capillary, with a net pressure of 4.8 kPa

   (c)

   Explain why the hydrostatic pressure of the blood is lower at the venule end of the capillary than at the arteriole end.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A child with severe protein deficiency has a swollen abdomen and swollen legs. A blood test shows that the concentration of proteins in the child's blood plasma is much lower than normal.

   (a)

   Which change in the child's blood is the most likely cause of the swelling?

   [1 mark]

   • AA lower oncotic pressure of the blood plasma
   • BA higher oncotic pressure of the blood plasma
   • CA lower hydrostatic pressure at the arteriole end
   • DA higher concentration of red blood cells

   (b)

   Which system normally returns tissue fluid that is not reabsorbed by the capillaries to the blood?

   [1 mark]

   • AThe excretory system
   • BThe nervous system
   • CThe lymph system
   • DThe digestive system

   (c)

   Explain how the low concentration of plasma proteins causes the swelling in the child's abdomen and legs.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   During cancer surgery, some of the lymph vessels in a woman's armpit were removed. Six months later her arm on that side is swollen, and the swelling does not go down overnight.

   (a)

   Describe how tissue fluid that is not reabsorbed by the capillaries is returned to the blood.

   [3 marks]

   (b)

   Explain why the removal of some lymph vessels from the woman's armpit has caused her arm to swell.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A shop assistant stands almost still for most of an eight-hour shift. By the end of the shift her ankles are swollen. By the next morning, after she has slept with her legs raised on a pillow, the swelling has gone.

   (a)

   Explain how tissue fluid is formed at the arteriole end of a capillary and how most of it is returned to the blood at the venule end, referring to hydrostatic and oncotic pressures.

   [6 marks]

   (b)

   Suggest why the woman's ankles become swollen after standing for a long time, and why raising her legs reduces the swelling.

   [6 marks]

   Total for question 4: 12 marks

End of questions