Circulatory system

• What does the circulatory system carry to every cell in the body?


  Food and oxygen
• Besides delivering substances, what is another function of the circulatory system?


  It collects waste products for removal from the body
• What are the main components of the circulatory system?


  The heart, blood vessels, and blood
• What type of circulatory system do humans have?


  A double circulatory system
• What happens in the first circuit of the double circulatory system?


  The right ventricle pumps deoxygenated blood to the lungs
• What occurs in the second circuit of the double circulatory system?


  The left ventricle pumps oxygenated blood to the body organs
• How does blood return to the heart after delivering oxygen to body cells?


  It returns as deoxygenated blood
• What is the primary function of the heart?


  To pump blood around the body
• What are the walls of the heart primarily made of?

  Muscle tissue
• What is the role of valves in the heart?


  To ensure blood flows in the right direction
• How does the heart pump blood through its chambers?


  1. Blood flows into the atria from the vena cava and pulmonary vein.
  2. The atria contract, pushing blood into the ventricles.
  3. The ventricles contract, forcing blood into the pulmonary artery and aorta.
  4. Blood flows to organs through arteries and returns through veins.
  5. The cycle starts over as the atria fill again.
• What arteries supply the heart with oxygenated blood?

  Coronary arteries
• What controls your resting heart rate?

  A group of cells in the right atrium wall that act as a pacemaker
• What do the pacemaker cells produce to control the heartbeat?


  A small electric impulse
• What is an artificial pacemaker used for?


  To control heartbeat if natural pacemaker cells fail
• What are the three types of blood vessels?

  1. Arteries
  2. Capillaries
  3. Veins
• What is the primary function of arteries?


  To carry blood away from the heart
• Why are artery walls strong and elastic?


  Because blood is pumped out at high pressure
• What is the lumen of an artery?


  The hole down the middle of the artery
• Why do capillaries have permeable walls?


  To allow substances to diffuse in and out
• What is the thickness of capillary walls?


  Usually only one cell thick
• What do capillaries supply to body cells?


  Food and oxygen
• What do capillaries take away from body cells?


  Waste products like CO₂
• What happens to capillaries as they join up?


  They form veins
• Why do veins have thinner walls than arteries?


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


  Veins have a bigger lumen than arteries
• What do veins have to help blood flow in the right direction?


  Valves
• How do you calculate the rate of blood flow?


  Rate of blood flow = volume of blood ÷ number of minutes
• If 1464 ml of blood passed through an artery in 4.5 minutes, what is the rate of blood flow?


  $325 \text{ ml/min}$
• If 2.175 litres of blood passed through a vein in 8.7 minutes, what is the rate of blood flow in ml/min?


  $250 \text{ ml/min}$
• What is blood classified as?


  A tissue
• What are the four main components of blood?

  1. Red blood cells
  2. White blood cells
  3. Platelets
  4. Plasma
• What is the primary function of red blood cells?


  To carry oxygen from the lungs to body cells
• What shape do red blood cells have and why?


  They are biconcave discs for a large surface area
• Why do red blood cells not have a nucleus?


  To allow more room to carry oxygen
• What pigment do red blood cells contain?

  Haemoglobin
• What happens to haemoglobin in the lungs?


  It binds to oxygen to become oxyhaemoglobin
• What happens to oxyhaemoglobin in body tissues?


  It splits into haemoglobin and oxygen
• What is the primary function of white blood cells?


  To defend against infection
• What process do some white blood cells use to engulf microorganisms?

  Phagocytosis