Cardiac

• The cardiovascular system is divided into two parts: the peripheral circulation and the pulmonary circulation
• Base


  The widest part of the heart
• Apex


  The bottom part of the heart
• The apex is shifted so it lies more anteriorly
• Pericardium


  • It is a fibrous sac that encloses the heart
  • It is divided into two parts: the fibrous pericardial sac and the serous pericardium
  • The pericardial sac is a loose tissue so the heart can beat inside it, but it is not elastic so it cannot stretch if the heart becomes abnormally enlarged
• Parietal layer of the serous pericardium


  • It lines the pericardial sac
• Visceral layer of the serous pericardium


  • It lies directly on the surface of the heart
• Pericardial space


  The area between the two pericardial membranes
• Pericardial fluid


  It lubricates the membranes and prevents friction between them during the motions and pulsations of the heart
• Wall of the heart


  • It has three layers: the epicardium, the myocardium, and the endocardium
• Epicardium


  The outermost layer of the heart wall
• Myocardium


  The middle, thick layer of the heart wall, made up of cardiac muscle
• Endocardium


  The innermost layer of the heart wall
• Cardiac muscle


  • It is autorhythmic and does not require external stimuli to contract and relax in a regular rhythm
  • It can continue beating from birth through adolescence, middle age, and old age without taking a break
• When the heart stops beating and is not restarted, the animal dies
• Epicardium


  The outermost layer of the heart
• Chambers of the heart


  • Two atria (upper chambers)
  • Two ventricles (lower chambers)
• Atria


  The upper chambers of the heart
• Ventricles


  The lower chambers of the heart
• Interatrial septum


  The wall separating the left and right atria
• Papillary muscles


  Nipple-like projections on the inside surface of the ventricles
• Chordae tendineae


  Fibrous cords that connect the papillary muscles to the valve cusps
• Atrioventricular (AV) valves


  The valves between the atria and ventricles
• Tricuspid valve


  The AV valve on the right side of the heart, with three cusps
• Bicuspid valve

  The AV valve on the left side of the heart, with two cusps, mitral valve
• Semilunar valves


  The valves that control blood flow out of the ventricles and into the arteries, pulmonary and aortic
• Skeleton of the heart

  • It is located between the atria and ventricles
  • It is made up of dense connective tissue rings
  • It separates the atria and ventricles
  • It anchors the heart valves
  • It provides some electrical insulation between the atria and ventricles
• Coronary arteries


  Arteries that supply blood to the cardiac muscle
• Cardiac nerves


  Nerves that regulate the heart's contractions and relaxations
• Cardiac tamponade is a condition where the pericardial sac is overfilled with fluid, preventing the heart from expanding normally between beats
• Blood flow through the heart

  1. Deoxygenated blood enters right atrium

  2. Flows through tricuspid valve to right ventricle

  3. Pumped through pulmonary valve to pulmonary circulation

  4. Oxygenated blood returns to left atrium

  5. Flows through mitral valve to left ventricle

  6. Pumped through aortic valve to systemic circulation
• The heart has a rhythmic, coordinated contraction to ensure blood flow
• The two sides of the heart pump blood to different areas at the same time
• Cardiac cycle


  1. Ventricles fill with blood

  2. AV valves close, semilunar valves open

  3. Ventricles contract, pumping blood out

  4. Semilunar valves close, AV valves open

  5. Ventricles fill again
• Cardiac valvesThey open and close to control the direction of blood flow
• Closing of cardiac valves produces the 'heartbeat' sounds
• Systole


  The contraction of the cardiac muscle
• Diastole


  The relaxation of the cardiac muscle
• Abnormal heart sounds can indicate valve problems or blood flow issues
• Cardiac output


  The volume of blood pumped out of the left ventricle per minute