The Nature of Science Structure and function of the blood vessels
Artery Thick-walled, elastic blood vessels that usually carry oxygen-rich blood away from the heart.
Capillary Smallest blood vessel. Oxygen, nutrients, carbon dioxide and other substances can diffuse easily through the thin walls.
Vein Thin-walled, inelastic blood vessels that usually carry carbon dioxide-rich blood back to the heart. Veins have valves that stop blood from flowing backwards.
Artery Outer wall Thick muscular wall
Arteries Feature
Thick elastic walls
Veins Feature
Valves present
Capillaries Feature
90 Vein
Outer wall Thin muscular wall
Fig. 6 Cross section of an artery, a vein and a capillary. Why this is important
Allows the artery to expand and contract as the blood is pushed through under high pressure.
Why this is important
Thin inelastic walls No expansion and contraction of the veins as blood is pushed through under low pressure.
Pressure is low in the veins so valves are necessary to prevent the blood from flowing backwards.
Why this is important
Walls are only one Substances like gases and nutrients can be exchanged easily between cell thick
