B2.11 Blood vessels and Blood

• Arteries carry blood ___________ the heart.

  away from
• Capillaries carry blood through the body tissues, allowing oxygen, nutrients, and waste products, to be exchanged between tissues and the blood.
• Veins carry blood ___________ the heart.

  towards
• • Arteries are large and carry blood at a very high pressure.
  • Artery walls have a thick middle layer, containing both muscle and elastic tissue.
  • The muscle tissue provides strength, and allows the arteries to direct blood flow.
  • The elastic tissue allows the arteries to stretch and recoil.
  • Compared to their walls, arteries have a relatively narrow lumen, which keeps the blood pressure high.

  
• • Capillaries are the smallest of the three blood vessels.
  • The role of capillaries is to exchange nutrients and waste products with the tissues.
  • Capillary walls are permeable, meaning substances are able to move through them.
  • Their walls are also only one cell thick which means a short distance for diffusion.
  • Capillaries carry blood at a low pressure and have a lower rate of flow than arteries

  
• What substances are nutrients that are exchanged between the blood in the capillaries and the body tissues?

  • Glucose
  • Amino acids
• What system did we introduce in the last video?

  The circulatory system
• What is the primary function of the heart in the circulatory system?

  It acts as the system's pump
• What are the three types of blood vessels discussed?

  Arteries, capillaries, and veins
• What do arteries do with blood?

  Carry blood away from the heart
• What is the role of capillaries in the circulatory system?

  Exchange nutrients and oxygen with tissues
• What do veins do with blood?

  Carry blood back to the heart
• How is the structure of arteries related to their function?

  They need to withstand high blood pressure
• Why do arteries have thick walls?

  To bear high pressures from pumped blood
• What two types of tissue make up the walls of arteries?

  Muscle tissue and elastic tissue
• What is the lumen of a blood vessel?

  The hole or space in the middle
• How do capillaries facilitate substance exchange?

  They have walls that are one cell thick
• What is the total cross-sectional area of capillaries compared to arteries?

  It is much larger than for arteries
• Why does blood flow more slowly in capillaries?

  Because the pressure is much lower
• What do veins have that prevents blood from flowing backwards?

  Valves
• Why do veins have relatively thin walls?

  Because the blood is at low pressures
• How do you calculate the rate of blood flow?

  Divide blood volume by time
• If 2500 ml of blood passes through the aorta in 8 minutes, what is the flow rate?

  320 ml per minute
• What is the aorta?

  The big artery that leaves the heart
• What is the main purpose of the video?

  To explain blood vessels in the circulatory system
• What are the key functions of arteries, capillaries, and veins?

  • Arteries: Carry blood away from the heart
  • Capillaries: Exchange nutrients and oxygen with tissues
  • Veins: Carry blood back to the heart
• How do the structures of arteries, capillaries, and veins relate to their functions?

  • Arteries: Thick walls for high pressure
  • Capillaries: Thin walls for substance exchange
  • Veins: Thin walls and valves for low pressure
• • The role of veins is to carry blood from the body (or lungs) back to the heart.
  • Veins are a similar size to arteries, but they have relatively thin walls and a relatively wide lumen
  • This is because they carry blood at a much lower pressure.
  • Veins also contain valves to prevent the blood from flowing backwards.

  
• Name some substances that are exchanged between the blood in the capillaries, and the body tissues:

  • Carbon dioxide
  • Glucose
  • Oxygen
  • Urea
• Artery

  You can tell X is an artery because it has a relatively small lumen (the light pink bit in the middle) and thick walls (the darker pink/purple layers).

  
• If you consider all the blood vessels inside of a human body, which type of blood vessel accounts for the majority of the cross-sectional area?

  • Capillaries 
  • Even though individual capillaries have a very small cross-section, there are so many of them that together they have the highest total cross-section. 
• In which order does blood flow through the three types of blood vessels? 

  Heart ➔ arteries ➔ capillaries ➔ veins ➔ heart
• What is the role of red blood cells?

  To carry oxygen from the lungs to the tissues 
• Red blood cells are packed full of a large proteins called haemoglobin, which bind to oxygen. 
• How are red blood cells adapted for their function?

  • They have a biconcave shape to increase their surface area
  • They have no nucleus to fit in more haemoglobin 
• What is the role of white blood cells?

  To defend against pathogens 
• Phagocytosis is the process by which a white blood cell binds to, and then engulfs a pathogen, in order to destroy it. 
• How do antibodies help defend against pathogens? 

  They bind to pathogens and help immune cells destroy them
• Do white blood cells have a nucleus? 

  Yes
• What is the role of platelets?

  To clot the blood when a blood vessel breaks