blood vessels

• What are the three main types of blood vessels?

  Arteries, capillaries, and veins
• What is the primary function of arteries?

  To carry blood from the heart
• What is the role of capillaries in the circulatory system?

  To exchange materials with tissues
• What do veins do in the circulatory system?

  They carry blood to the heart
• Why are artery walls strong and elastic?

  Because the heart pumps blood at high pressure
• How do the walls of arteries compare to the size of their lumen?

  The walls are thick compared to the size of the lumen
• What features do arteries have to support their function?

  Thick layers of muscle and elastic fibres
• What do arterioles branch into?

  Capillaries
• How thick are capillary walls?

  Only one cell thick
• What substances do capillaries supply and remove?

  They supply food and oxygen, and remove waste like CO2
• What are networks of capillaries in tissues called?

  Capillary beds
• Why are capillaries described as really tiny?

  Because they are too small to see
• How do the walls of capillaries facilitate diffusion?

  By being permeable and one cell thick
• What do capillaries branch into?

  Venules
• How do venules relate to veins?

  Venules eventually join up to form veins
• Why do veins have thinner walls than arteries?

  Because the blood is at lower pressure in the veins
• What is the lumen size comparison between veins and arteries?

  Veins have a bigger lumen than arteries
• What feature do veins have to assist blood flow?

  Valves to help keep the blood flowing in the right direction
• What type of muscle and fibres do veins contain?

  Smooth muscle and elastic fibres