book (ch9)

• Circulatory system


  A system of blood vessels with a pump and valves to ensure one-way flow of blood
• Valves


  Structures that allow a liquid to flow in one direction only
• Oxygenated blood


  Blood containing a lot of oxygen
• Deoxygenated blood


  Blood containing only a little oxygen
• Double circulatory system


  • Blood passes through the heart twice on one complete circuit of the body
  • Consists of pulmonary system (blood vessels to and from lungs) and systemic system (blood vessels to and from rest of body)
• Single circulatory system


  • Blood passes through the heart only once on one complete circuit of the body
• Double circulatory system


  Provides respiring cells with oxygen more quickly than a single circulatory system
• Atria (singular: atrium)


  The thin-walled chambers at the top of the heart, which receive blood
• Ventricles


  The thick-walled chambers at the base of the heart, which pump out blood
• Septum


  The structure that separates the left and right sides of the heart, keeping oxygenated blood separate from deoxygenated blood
• Pulmonary veins


  The veins that carry oxygenated blood from the lungs to the left atrium of the heart
• Venae cavae (singular: vena cava)


  The large veins that bring deoxygenated blood to the right atrium
• Aorta


  The largest artery in the body, which receives oxygenated blood from the left ventricle and delivers it to the body organs
• Pulmonary artery


  The artery that carries deoxygenated blood from the right ventricle to the lungs
• Atrioventricular valve


  A valve between an atrium and a ventricle in the heart, which allows blood to flow from the atrium to the ventricle but not in the opposite direction
• Semilunar valves


  Valves close to the entrances to the aorta and pulmonary artery, which prevent backflow of blood from the arteries to the ventricles
• Blood flow through the heart


  1. Left atrium

  2. Left ventricle

  3. Aorta

  4. Body

  5. Right atrium

  6. Right ventricle

  7. Pulmonary artery

  8. Lungs

  9. Left atrium
• The left ventricle has an especially thick wall of muscle to enable it to pump blood to the rest of the body
• The blood flowing to the lungs in the pulmonary artery has a much lower pressure than the blood in the aorta
• Arteries carry blood away from the heart
• Veins carry blood towards the heart
• How blood is pushed out of the heart


  The muscles in the walls of the ventricles contract, producing a large force that squeezes inwards on the blood inside the heart and pushes it out
• Septum


  Keeps oxygenated blood and deoxygenated blood separate from one another in the heart
• It is important for oxygenated and deoxygenated blood to be kept separate in the heart so that the blood can be efficiently circulated around the body
• The atria have thinner walls than the ventricles because the atria simply receive blood, while the ventricles pump blood out of the heart and around the body
• Coronary arteries


  Vessels that deliver oxygenated blood to the heart muscle
• Coronary heart disease (CHD)


  Disease caused by blockage of the coronary arteries
• Blockage of the coronary arteries can cause the cardiac muscle to not get any oxygen, leading to the heart stopping beating
• How coronary heart disease is caused


  1. Cholesterol deposits build up inside the walls of arteries

  2. Deposits make the artery wall stiffer and the lumen narrower

  3. Blood clots can form

  4. Blockage of the coronary arteries stops blood flow to cardiac muscle
• Blockage of the coronary arteries is a very common cause of illness and death, especially in developed countries
• Normal ECG


  • Graph with time on x-axis and electrical activity on y-axis
  • Points labelled P, Q, R, S and T represent different stages in one heartbeat
• How the heart beats


  1. Muscles in heart walls contract and relax

  2. Contraction squeezes blood out

  3. Relaxation allows blood to flow in

  4. Atrioventricular valves open and close to control blood flow
• The semilunar valves shut to prevent blood from flowing into the ventricle
• The valves in the veins are forced shut by the pressure of the blood, stopping the blood from flowing back into the veins
• As the walls of the atria contract, they increase the pressure of the blood in the atria, pushing down on the atrioventricular valves and allowing blood to flow through
• When the ventricles contract, the atrioventricular valves are pushed closed again by the pressure of the blood in the ventricles
• Arteries


  Thick-walled vessels that take high-pressure blood away from the heart
• Capillaries


  Tiny vessels with walls only one cell thick, that take blood close to body cells
• Veins


  Thin-walled vessels that take low-pressure blood back to the heart
• Arteries have elastic tissue in their walls which can stretch and recoil with the force of the blood, helping to make the flow smoother