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• When most people hear the term cardiovascular system, they immediately think of the heart
• The cardiovascular system delivers oxygen and nutrients to the body tissues and carries away wastes such as carbon dioxide via blood
• The heart pumps blood throughout the body in blood vessels
• Blood flow requires both the pumping action of the heart and changes in blood pressure
• Pericardium


  Sac that encloses the heart, made up of an outer fibrous layer and an inner serous membrane pair
• Fibrous pericardium


  Loosely fitting superficial part of the pericardial sac that helps protect the heart and anchor it to surrounding structures
• Serous pericardium


  Slippery, two-layered inner part of the pericardial sac
• Parietal pericardium


  Lining of the interior of the fibrous pericardium
• Visceral pericardium


  Outermost layer of the heart wall, continuous with the parietal pericardium
• Pericardial cavity


  Space between the parietal and visceral layers of the serous pericardium, containing lubricating serous fluid
• Myocardium


  Thick bundles of cardiac muscle that make up the middle layer of the heart wall and contract to pump blood
• Endocardium


  Thin, glistening lining of the heart chambers, continuous with the linings of the blood vessels
• Atria


  The two superior, receiving chambers of the heart
• Ventricles


  The two inferior, discharging chambers of the heart that pump blood out of the heart
• Interatrial septum


  The wall dividing the atria
• Interventricular septum


  The wall dividing the ventricles
• The right side of the heart functions as the pulmonary circuit pump, receiving oxygen-poor blood from the body and pumping it to the lungs
• The left side of the heart functions as the systemic circuit pump, receiving oxygen-rich blood from the lungs and pumping it to the body
• The left ventricle has thicker walls than the right ventricle because it pumps blood over the much longer systemic pathway through the body
• Atrioventricular (AV) valves


  Valves located between the atria and ventricles that prevent backflow into the atria when the ventricles contract
• Bicuspid (mitral) valve


  The left AV valve with two cusps
• Tricuspid valve


  The right AV valve with three cusps
• Chordae tendineae


  Tiny white cords that anchor the AV valve cusps to the ventricular walls
• Operation of the AV valves

  1. Ventricles contract, forcing blood against AV valve cusps

  2. AV valves close, with chordae tendineae tightening to prevent valve cusps from everting into atria

  3. As ventricles fill, AV valve cusps hang limply into ventricles

  4. Atria contract, forcing additional blood into ventricles

  5. AV valves open as atrial pressure exceeds ventricular pressure

  6. AV valves close as ventricular pressure exceeds atrial pressure
• Semilunar valves


  Valves guarding the bases of the pulmonary trunk and aorta, each with three cusps that fit tightly together when closed
• Operation of the semilunar valves

  1. As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open

  2. As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close
• Heart valves


  • Atrioventricular (AV) valves
  • Semilunar valves
• AV valves


  • If cusps were unanchored, they would blow upward into the atria like an umbrella
  • Prevent backflow into the atria when the ventricles are contracting
• Semilunar valves


  • Guard the bases of the two large arteries leaving the ventricular chambers
  • Each has three cusps that fit tightly together when the valves are closed
  • Forced open when the ventricles are contracting and forcing blood out of the heart
  • Close when the ventricles relax to prevent arterial blood from reentering the heart
• • The AV valves are open during heart relaxation and closed when the ventricles are contracting
  • The semilunar valves are closed during heart relaxation and are forced open when the ventricles contract
• The valves force blood to continually move forward through the heart by opening and closing in response to pressure changes
• Severely deformed valves can seriously hamper cardiac function
• Incompetent valve


  Forces the heart to pump and repump the same blood because the valve does not close properly, so blood backflows
• Valvular stenosis


  The valve cusps become stiff, often because of repeated bacterial infection of the endocardium, forcing the heart to contract more vigorously than normal to create enough pressure to drive blood through the narrowed valve
• The functional blood supply that oxygenates and nourishes the myocardium is provided by the right and left coronary arteries
• The coronary arteries and their major branches are compressed (flow is inhibited, not stopped completely) when the ventricles are contracting and fill when the heart is relaxed
• The myocardium is drained by several cardiac veins, which empty into the coronary sinus, which in turn empties into the right atrium
• Angina pectoris


  Crushing chest pain caused by the myocardium being deprived of oxygen
• Myocardial infarction (MI)


  Commonly called a "heart attack" or a "coronary", caused by oxygen-deprived heart cells dying and forming an infarct
• Cardiac muscle cells can and do contract spontaneously and independently, even if all nervous connections are severed