Heart LO7

7.) Identify the unique structures of the left ventricle.

L. atrioventricular (mitral, bicupsid) valve

  • Composed of two valve cusps (anterior & posterior) which attach to the fibrous ring surrounding the right AV orifice
    • Cusps are drawn together before L. ventricular contraction, thus preventing the flow of blood from the L. atrium to the L. ventricle to direct the flow of blood through the pulmonary valve
    • Close during systole; open during diastole
  • Chordae tendineae: thin cords that attach to neighboring valve cusps from the papillary muscles
  • Papillary muscles: two muscles that attached to the ventricular wall
    • Anterior & posterior papillary muscles

Trabeculae carneae: numerous in the L. ventricle

  • The heart walls of the L. ventricle are significantly thicker than in the R. ventricle due to the higher arterial pressure associated with systemic circulation

Aortic vestibule: smooth-walled portion of the L. ventricle leading into the aortic orifice

Aortic orifice: at the orifice, there is a transition from ventricle to ascending aorta

Aortic (semilunar) valve

  • Has three, semilunar cusps (posterior, right, and left)
  • Close during diastole; open during systole
  • When blood is pumped through the L. ventricle into the ascending aorta, the cusps project into the trunk
    • When relaxation of the ventricle occurs, the cusps meet (‘snap close’) to prevent blood from returning to the ventricle
    • Aortic sinuses (of Valsalva): dilations of the ascending aorta just superior to the cusps of the aortic valve (there are also sinuses of the pulmonary trunk)
      • The right coronary a. (RCA) and the left coronary a. (LCA) originate in the upper portions of the R. and L. aortic sinuses, respectively