7.4 The structure of the heart

• The heart consists of two separate pumps:

  1. Left pump
  2. Right pump
• The left pump of the heart deals with oxygenated blood from the lungs
• The right pump of the heart deals with deoxygenated blood from the body
• Each pump of the heart has two chambers:

  • Atrium
  • Ventricle
• The Atrium has a thinner wall and is elastic and stretched as it collects blood
• The Ventricle has a much thicker muscular wall because it needs to contract strongly to pump blood some distance, either to the lungs or the rest of the body
• Two separate pumps of the heart is necessary because:

  • Blood has to pass through tiny capillaries in the lungs to present a large surface area for gas exchange
  • There is a large decrease in pressure and so blood flow to the rest of the body would be very slow
  • Mammals' system allows blood to be returned to the heart in order to increase pressure before it is distributed to the rest of the body
  • Essential to prevent the mixture of deoxygenated and oxygenated blood
• The right ventricle has a thinner muscular wall so it can pump blood only to the lungs
• The left ventricle has a thick muscular wall which enables it to contract to create enough pressure to pump blood to the rest of the body
• Both atria contract together and the both ventricles contract together - pumping blood at the same volume
• Between each atrium and ventricle are valves that prevent the backflow of blood into the atria when the ventricles contract:

  • The left atrioventricular valve
  • The right atrioventricular valve
• Each of the four chambers of the heart is connected to large blood vessels that carry blood towards or away from the heart
• Ventricles pump blood away from the heart and into the arteries
• Atria receive blood from the veins
• Pulmonary vessels are vessels connecting the heart to the lungs

  • Aorta
  • Vena cava
  • Pulmonary artery
  • Pulmonary vein
• The Aorta is connected to the left ventricle and carries oxygenated blood to all parts of the body except the lungs
• Vena cava is connected to the right atrium and brings deoxygenated blood back from the tissues of the body, except the lungs
• The Pulmonary artery is connected to the right ventricle and carries deoxygenated blood to the lungs, where its oxygen is replenished and its carbon dioxide is removed
• The Pulmonary vein is connected to the left atrium and brings oxygenated blood back from the lungs to the heart
• The heart is supplied with oxygenated blood by its own blood vessels called coronary arteries
• • The blockage of coronary arteries may lead to myocardial infarction or heart attack
  • This is because an area of the heart muscle is deprived of blood so of oxygen also
  • Muscle cells are unable to do aerobic respiration leading to cell death