HEART CHAMBERS AND VALVES

• Heart


  Consists of four chambers: two upper chambers (right and left atria) and two lower chambers (right and left ventricles)
• Septum

  Partition that separates the right and left sides of the heart
• Atria


  • Thin-walled, receive blood returning to the heart and pump blood into the ventricles
• Ventricles


  • Thicker-walled, pump blood out of the heart
• The left ventricle is thicker than the right ventricle because the left side of the heart has a greater workload
• Atrioventricular (AV) valves


  One-way valves located at the entrance into the ventricles
• AV valves


  • Tricuspid valve (three cusps, between right atrium and right ventricle)
  • Bicuspid (mitral) valve (two cusps, between left atrium and left ventricle)
• Chordae tendineae


  • Collagen fibers that anchor the AV valve flaps to papillary muscles within the ventricles
• AV valve function


  1. Open to allow blood flow from atria to ventricles

  2. Snap shut during ventricular contraction to prevent regurgitation

  3. Prevented from blowing open in reverse direction by anchors to papillary muscles
• Semilunar valves


  One-way valves located at the exit of each ventricle at the beginning of the great vessels, each with three cusps that look like half-moons
• Semilunar valves


  • Pulmonic valve (at entrance of pulmonary artery from right ventricle)
  • Aortic valve (at beginning of ascending aorta from left ventricle)
• Semilunar valve function


  1. Open during ventricular contraction

  2. Close from pressure of blood when ventricles relax, preventing backward flow