the heart

• right atrium:

  • thin muscular walls as blood under low pressure
  • one way valve (entry of vena cava) to prevent backflow of blood into great veins
• right ventricle

  • lungs are relatively close to the heart
  • ventricular walls: able to build sufficient pressure to move the blood into the lung capillaries from pulmonary artery
  • not as high pressure - lung capillaries burst
• septum:

  • inner divided wall of heart
  • not complete until after birth: mixing of blood in fetus - after birth, gap closes
• semi-lunar valves:

  • 3
  • inside aorta and pulmonary artery
  • prevents backflow of blood into ventricles
• chordae tendinae

  • string-like structures
  • attached to edges of valve cusps : prevents valve flaps from going inside out
• left atrium:

  • thin walled chamber
• left ventricle

  • very thick muscular wall
  • thicker than right ventricle because...
  • has to produce sufficient force to move the blood under pressure to all the extremities
• heart disease:

  • narrow coronary artery - angina
  • blocked coronary artery - myocardial infarct
• pressure in blood in aorta is high
• pressure in tissue fluid is low
• pressure in lymph is low
• pressure in blood in vena cava is low