Blood Vessels - The Transport Network
Arteries are like motorways for your blood - they're built tough with thick, elastic walls because they handle high-pressure blood flowing away from your heart. These elastic fibres are brilliant because they stretch when blood surges through, then spring back to keep the pressure steady.
Veins have a much easier job, carrying blood back to your heart at low pressure. Since there's less force pushing the blood along, veins have special valves to stop blood flowing backwards - think of them as one-way gates.
Capillaries are where the real magic happens. These tiny vessels have walls just one cell thick, making it super easy for oxygen, nutrients, and waste to pass through. They're so narrow they can squeeze between your cells, getting close enough for efficient exchange.
Remember: Arteries = Away from heart (high pressure), Veins = back to heart (low pressure), Capillaries = exchange sites (one cell thick).