Capillaries

• Exchange nutrients + oxygen with tissues.
• really small
• ·      Exchange substances with cells (nutrients + oxygen)
• ·      Take away waste products (CO2)
• Single cell thick + permeable.
• ·      Lumen is tiny.
• Total cross area huge because there is so many
• ·      Lower blood pressure which means it flows slower.
• ·      Because blood flows slowly gas exchange has time to happen.
• ·      Enough time for O2/CO2/nutrient exchange.