1. 1
   A technician examined cross-sections of three types of blood vessel taken from a mammal: one had a thick muscular wall with a narrow lumen and no valves, another had a thinner wall with a wider lumen and valves, and the third had a wall only one cell thick.

   (a)

   Which vessel had these features?

   [1 mark]

   • AArtery
   • BVein
   • CCapillary
   • DLymph vessel

   (b)

   Which vessel in the technician's samples had a wall only one cell thick?

   [1 mark]

   • AAorta
   • BArtery
   • CVein
   • DCapillary

   (c)

   Explain how the thin, one-cell-thick wall of the vessel identified in part (a) is related to its function.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A researcher measured blood pressure at different points along the circulatory system of an animal and found the highest pressure recorded near the heart in one type of vessel, with pressure dropping steadily as blood travelled further from the heart.

   (a)

   In which vessel was the highest pressure recorded?

   [1 mark]

   • ACapillary
   • BVein
   • CArtery
   • DVenule

   (b)

   Which feature of the vessel with the highest blood pressure allows it to withstand this high pressure without bursting?

   [1 mark]

   • AA very thin, one-cell-thick wall
   • BA thick wall containing muscle and elastic fibres
   • CThe presence of valves along its length
   • DA wide lumen relative to wall thickness

   (c)

   Explain why blood pressure gradually decreases as blood travels further away from the heart through the circulatory system.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A patient with varicose veins had faulty valves in the veins of their legs, causing blood to pool and flow backwards under gravity. Their doctor also examined the arteries supplying the patient's legs and found them functioning normally with no valves present.

   (a)

   Explain why faulty valves in leg veins specifically cause this problem.

   [3 marks]

   (b)

   A patient with varicose veins had faulty valves in the veins of their legs, causing blood to pool and flow backwards under gravity. Explain why the arteries supplying the patient's legs do not need valves to prevent backflow in the same way that the leg veins do, and outline three structural differences between arteries and veins that account for this.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A physiology lecturer prepared microscope slides of an artery, a vein and a capillary bed taken from the same region of an animal's leg, to compare their structures and relate each to its role in the circulatory system.

   (a)

   Describe the structure of arteries, veins and capillaries, and explain how each structure is adapted to the specific function that vessel performs in the circulatory system.

   [6 marks]

   (b)

   Blood samples taken just before and just after passing through a capillary bed in active muscle tissue showed a large fall in oxygen concentration and a large rise in carbon dioxide concentration. Explain, in terms of capillary structure and diffusion gradients, why exchange is so efficient in this capillary bed, and discuss how this exchange would differ if the muscle were resting rather than actively contracting.

   [6 marks]

   Total for question 4: 12 marks

End of questions