Blood Vessels

Question 1

Describe the structure and function of a vein.

Answer 1

Veins carry blood towards the heart.
They have thinner walls and a wider lumen than arteries, and carry blood at low pressure.
They contain valves to prevent blood flowing backwards.

Question 2

Describe the structure and function of an artery.

Answer 2

Arteries carry blood away from the heart.
They have relatively thick walls to withstand the high pressure.
The lumen is narrow to maintain the high pressure.
The walls contain thick layers of muscle for strength, and elastic fibres to stretch under the pressure.

Question 3

Describe the structure of capillaries.

Answer 3

Capillaries carry blood close to body cells to exchange substances ; such as nutrients and oxygen, and waste like CO2 and urea.
They are permeable so that substances can diffuse across, and are one cell thick so that the diffusion pathway will be shorter.