Blood Vessels

• pressure in the arteries is high, blood moves from heart to organ. arteries are impermeable , they contain elastic fibres and muscle tissue , contains oxygenated blood (excluding pulmanory artery). lumen is small, they can constrict
• pressure in the veins is low, blood moves to heart. veins are impermeable , they contain few elastic fibres and muscle tissue , contains deoxygenated blood (excluding pulmanory vein). lumen is large, contains valves
• pressure in the capillaries is low, connects arteries and veins. capillaries are permeable (site of gaseous exchange) , tissue is only one cell thick , contains oxygenated and deoxygenated blood . lumen is small