The Heart

• • Vasodilation - widening of arteries
  • Vasoconstriction - narrowing or arteries
• ARTERIES

  AVC - order of largeness

  • Carry blood away from heart - high pressure
  • Are elastic to maintain blood pressure
  • Rings of muscle to adjust diameter and change blood flow to parts of body
• CAPILLARIES

  • Thin walled
  • Join arteries and veins
  • Allow gas exchange
• VEINS

  • Thin walls - low blood pressure
  • Valves to prevent backflow
  • Lumen
• PATHWAY OF BLOOD

  1. Blood enters right atrium through vena cava
  2. Passes to right ventricle through atrioventricular valve
  3. Blood goes to lungs by pulmonary artery
  4. In lungs, gaseous exchange occurs and blood becomes oxygenated
  5. Blood goes to left atrium by pulmonary vein and goes to left ventricle by atrioventricular valve
  6. Blood leaves ventricle by aorta into body
• CARDIAC CYCLE

  • Repeated contraction and relaxation of heart
  • When heart beats, blood passes through vessels and chambers
  • Both right and left side heart contract and relax at same time
  • Diastole - ventricles relax, heart fills with blood
  • Systole - ventricles contract, blood is ejected and pumped into arteries
  • Cardiac cycle is complete when heart fills with blood and blood is then pumped out