BI-1104
Arteries, veins and capillaries
Biology · Secondary 3 · Hard · Arteries, veins and capillaries
In a normal leg vein, valves ensure blood flows only towards the heart. In a varicose vein, some valves are damaged and do not close properly. Which statement best explains why varicose veins become enlarged?
- Blood flows faster through the vein, causing the wall to thicken and bulge outwards.
- Backflow of blood increases pressure, stretching the thin vein wall so it swells and twists.
- The vein wall contains more elastic tissue than arteries, so it contracts and becomes lumpy.
- Valves in the vein close too tightly, trapping less blood and making the vein appear larger.
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