The mammalian heart

• what is the function of the vena cava?

  • transports deoxygenated blood from the body/tissues to the right atrium
• what is the function of the pulmonary artery?

  • transports deoxygenated blood from the right ventricle to the lungs
• what is the function of the pulmonary vein?

  • transports oxygenated blood from the lungs to the left atrium
• what is the function of the aorta?

  • transports oxygenated blood from the left ventricle to the body/tissue
• what is the function of the atria?

  • walls made of cardiac muscle, contracts therefore pumping blood to the ventricles
• what is the function of the ventricles?

  • walls made of cardiac muscle, contracts therefore pumping blood out of the heart into the arteries
• what is the function of the atrioventricular valves?

  • prevent back flow of blood from the ventricles into the atria
• what is the function of the tendinous cords?

  • hold the atrioventricular valves in place, therefore preventing them from turning inside out
• what is the function of the semi-lunar valves?

  • prevent back flow of blood from the arteries into the ventricles
• what is the function of the ventricular septum?

  • separates the left and right side, stopping oxygenated and deoxygenated blood mixing
• what is the function of the coronary artery?

  • supplies the heart muscle with blood and therefore oxygen and other nutrients
• what happens to the pressure of the blood when the muscles in the chamber walls contract?

  pressure increases because volume of chamber decreases
• why is the muscle of the two atria very thin?

  • distance the blood has to travel is very small (atria to ventricle)
  • there is only a small resistance to overcome
  • only a small hydrostatic pressure is needed to overcome resistance
  • only a small force of contraction is needed to generate pressure
  • thinner muscle wall is sufficient to generate small force of contraction
• why is the muscle wall of the right ventricle thicker than the right atria?

  • right ventricle has to pump blood further distance to the lungs than the right atria, which only has to pump to right ventricle
  • a larger resistance to overcome
  • a larger hydrostatic pressure is needed to generate this pressure
  • a larger force of contraction is needed to generate this pressure
  • a thicker muscle wall is required to generate this larger force of contraction
• what is the cause of a myocardial infarction?

  • blockage of coronary artery - become narrow by fatty deposits
  • reduces blood flow to cardiac muscles
  • cardiac muscles don’t receive enough oxygen and glucose and can die (tissue death)
• how does the atrioventricular valve work?

  Valve open:

  • greater pressure in atria than the ventricles
  • blood forces the valve open Valve closed:
  • tendinitis cords stop valve inverting
  • greater pressure in ventricles than atria
  • blood forced into pockets behind valve which closes it
• how does the semilunar valve work?

  Valve open:

  • greater pressure on the heart side of valve
  • blood forces the valve open Valve closed:
  • greater pressure on the artery-side of the valve
  • blood forced into the pockets behind the valve, which closes it
• label the diagram

  A) aortic arch

  B) pulmonary artery

  C) pulmonary veins

  D) left atrium

  E) left ventricle

  F) cardiac vein

  G) superior vena cava

  H) right pulmonary arteries

  I) right atrium

  J) coronary artery

  K) right ventricle

  L) inferior vena cava