The blood vessels and the blood

• 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 role do capillaries play in the circulatory system?

  They are involved in the exchange of materials at the tissues
• What is the function of veins in the circulatory system?

  To carry blood to the heart
• How do arterioles relate to capillaries?

  Arterioles branch into capillaries
• What is the relationship between capillaries and venules?

  Capillaries branch into venules
• Why are artery walls strong and elastic?

  Because the heart pumps blood out at high pressure
• What is the significance of the thickness of artery walls?

  They are thick compared to the size of the lumen
• What features of arteries allow them to stretch and spring back?

  They contain elastic fibers
• What is the thickness of capillary walls?

  Only one cell thick
• What are capillary beds?

  Networks of capillaries in tissue
• How do capillaries facilitate the exchange of substances?

  They have permeable walls
• What substances do capillaries supply and remove?

  They supply food and oxygen, and take away waste like CO₂
• Why is the thickness of capillary walls important for diffusion?

  It increases the rate of diffusion by decreasing the distance
• How do veins differ from arteries in terms of pressure?

  The blood is at lower pressure in the veins
• What feature do veins have to help blood flow in the right direction?

  They have valves
• What is the lumen size comparison between veins and arteries?

  Veins have a bigger lumen than arteries
• How many miles of blood vessels does the human body contain?

  About 60,000 miles
• Why can capillaries only be seen with a microscope?

  Because they are really tiny
• What are the adaptations of veins for carrying blood back to the heart?

  • Thinner walls compared to arteries
  • Larger lumen to facilitate blood flow
  • Valves to prevent backflow of blood
• How are capillaries adapted to their function?

  • Walls are one cell thick for efficient diffusion
  • Permeable walls allow substances to diffuse in and out
  • Close proximity to cells for effective exchange of oxygen and nutrients
• How does the total cross-sectional area of blood vessels affect blood flow?

  It affects the speed and distribution of blood flow
• What is the role of the heart in the circulatory system?

  To pump blood throughout the body
• What happens to blood pressure as it moves from arteries to veins?

  Blood pressure decreases
• What is the significance of the elastic fibers in arteries?

  They allow arteries to stretch and spring back