Blood Vessels - 9.3

• Artery is a thick-walled vessel that carries high-pressure blood away from the heart.
• Capillary is a tiny vessel with walls only one cell thick, which takes blood close to the body cells.
• Vein is a thin-walled vessel that takes low-pressure blood back to the heart.
• Arteries- contain thick and strong layer of muscle and elastic tissue.

  Capillaries- very thin, one cell thick.

  Veins- quite thin, contain less muscle and elastic tissue than arteries.
• Arteries- relatively narrow lumen, varies with heartbeat walls can stretch and recoil.

  Capillaries- very narrow lumen, just wide enough for a red blood cell to pass through.

  Veins- wide lumen, contains valves.
• Arteries- strength and elasticity needed to withstand high blood pressure and pulsing of blood as it's pumped thru arteries by heart.

  Capillaries- don't need strong walls as most blood pressure is lost, thin walls and narrow lumen bring blood into close contact w cells.

  Veins- don't need strong walls, most blood pressure lost, wide lumen offers less resistance so blood flow is smoother and slower than in arteries and valves prevent backflow.
• Arteries divide to form capillaries which come together again to form veins.
• Hepatic veins- blood vessels that carry blood away from the liver.
• Hepatic portal vein- brings blood from digestive system so liver can process the food which has been absorbed before it travels to other parts of body.
• Hepatic artery- supplies oxygenated blood to the liver.