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Leaving certificate biology
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Unit 1Ecology theory5 Topics|1 Quiz
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Nutrient recycling4 Topics|1 Quiz
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Ecological relationships and population dynamics2 Topics
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Human impact on the ecosystem2 Topics
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Study of a grassland ecosystem3 Topics
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Responses in the Flowering Plant4 Topics|1 Quiz
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Unit 3Sexual reproduction in the flowering plant1 Topic
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The human reproductive system3 Topics
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The menstrual cycle2 Topics
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Pregnancy2 Topics
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The circulatory system4 Topics
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Blood5 Topics
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The heart5 Topics
Lesson 11, Topic 2
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Blood vessels
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Arteries
Arteries carry blood away from the heart.
They carry blood under high pressure causing them to expand as the heart beats (pulse)

Veins
Veins carry blood towards the heart.
They carry blood under low pressure so they require valves to prevent back flow of blood

When muscles contract they squeeze the veins and help to push blood back to the heart

Arteries vs veins

Capillaries
Capillaries are tiny tubes that link arterioles to venules.
Their function is to allow exchange between blood and tissues via tissue fluid.

Capillaries have thin walls just one cell thick and are porous
