Anatomy and Physiology

• The three layers of the heart wall are the epicardium, myocardium, and endocardium.
• 3 layers of the heart:

  Epicardium - outermost layer
• 3 layers of the heart:

  Myocardium - cardiac muscle cells (striated)
• Skeletal - striated - multi

  Cardiac - striated - uni

  Smooth - not striated - uni
• 3 layers of the heart:

  Endocardium - innermost
• Chambers of the Heart:

  1. Atrium - receives
  2. Ventricle - pumps
• Chambers of the Heart:

  1. Right - deoxygenated
  2. Left - oxygenated
• Chambers of the Heart:

  1. Right atrium - receives deoxygenated
  2. Right ventricle - pumps deoxygenated
  3. Left ventricle - pumps oxygenated
  4. Left atrium - receives oxygenated
• Chambers of the Heart:

  Left Ventricle - biggest chamber of the heart
• Chambers of the Heart

  The right atrium receives deoxygenated blood from the venous circuit, via the superior and inferior vena cava.
• Chambers of the Heart:

  The right ventricle pumps blood to the lungs via the pulmonary artery for oxygenation.
• Chambers of the Heart:

  The left atrium receives oxygenated blood from the lungs via the pulmonary veins.
• Chambers of the Heart:

  The left ventricle ejects blood to the systemic circulation via the aorta
• Pericardia


  These are the protective membranes covering the heart.
• Two layers of the pericardia.

  The outer layer is the parietal pericardium and the inner layer is the visceral pericardium. The space between the pericardia is called pericardial sac. It contains 5 to 20 mls. of fluids to prevent friction between the two layers of pericardia.
• Valves of the Heart:

  Atrioventicular Valve - separates atrium and ventricle.
• Valves of the Heart:

  Semilunar Valve - separates ventricle and major artery.
• Valves of the Heart:

  • The 2 AV (atrioventricular) valves are the tricuspid valve (right side) and mitral valve (left side).
  • The 2 semilunar valves are pulmonic valve (of the pulmonary artery) and aortic valve (of the aorta)
• Valves of the Heart:

  Mitral Valve - biggest valve
• Valves of the Heart:

  Bicuspid Valve - other name for mitral valve.
• Coronary Blood Supply

  Coronary Artery - sends oxygen to the heart.
• Coronary Blood Supply

  2 Branches of the coronary artery:

  • Right coronary artery (RCA).
  • Left coronary artery (LCA).
• Coronary Blood Supply

  RCA supplies right side of the heart (anterior, lateral and

  • right side of the heart (right atrium and right ventricle)
  • SA node
  • AV node.

  LCA divides into circumflex coronary artery and left anterior descending artery.

  • The cca supplies the left atrium, left ventricle (posterior).
  • The lada supplies the left ventricle, anterior aspect.
• Left Anterior Descending Artery when occluded - anterior wall infarct - fatal


  Left Anterior Descending Artery (LADA) is often referred to as the "widowmaker" or "killer artery".
• Coronary Blood Flow

  SVC or IVC - right atrium - tricuspid valve - right ventricle - pulmonary valve - pulmonary artery - lungs - pulmonary vein - left atrium mitral valve - left ventricle - aortic valve - aorta - systemic circulation
• Heart Sounds

  S1 (First Heart Sound)

  • Cause: S1 is produced by the closure of the AV valves.
  • Location: Best heard at the apex of the heart.
  • Timing: Occurs at the beginning of systole (the contraction phase of the heart).
  • Sound: Described as a "lub" sound in the "lub-dub" sequence.
• Heart Sounds

  S2 (Second Heart Sound)

  • Cause: S2 is produced by the closure of the SL Valves.
  • Location: Best heard at the base of the heart.
  • Timing: Occurs at the beginning of diastole (the relaxation phase of the heart)
  • Sound: Described as a "dub" sound in the "lub-dub" sequence.
• Heart Sounds

  S3 (Third Heart Sound)

  • Cause: S3 is caused by the rapid filling of the ventricles during early diastole.
  • Location: Best heard at the apex with the bell of the stethoscope.
  • Timing: Occurs shortly after S2.
  • Sound: Described as a soft, low-pitched "gallop" sound, often termed the "ventricular gallop."
  • Clinical Significance: An S3 sound is normal in < 30 years old, and pregnant women. In older adults, it may indicate heart failure.
• Heart Sounds

  S4 (Fourth Heart Sound)

  • Cause: S4 is caused by the atria contracting forcefully to push blood into a stiff or hypertrophic ventricle during late diastole.
  • Location: Best heard at the apex with the bell of the stethoscope, just before S1.
  • Timing: Occurs right before S1, during the late filling phase of diastole (often referred to as the "atrial kick").
  • Sound: Described as a low-pitched "gallop" sound, often termed the "atrial gallop."
  • Clinical Significance: Hypertension
• Conduction system of the Heart

  The SA (sinoatrial) node is the natural pacemaker of the heart. It triggers 60 to 100 electrical firings per minute.
• Conduction system of the Heart

  The AV (atrioventricular) node triggers 40 to 60 electrical firings per minute.
• Conduction System of the Heart

  The Bundle of His divides into the right and left Bundle of His, and ends as Purkinje fibers. The Bundle of His and Purkinje fibers trigger 20 to 40 electrical firings per minute.
• Conduction System of the Heart

  Bundle of His (AV Bundle): From the AV node, the impulse travels down the Bundle of His, which is located in the interventricular septum. This bundle divides into two branches:

  • Right Bundle Branch: Transmits impulses to the right ventricle.
  • Left Bundle Branch: Transmits impulses to the left ventricle.
• Conduction System of the Heart

  The AV node slows the electrical impulse slightly, allowing the ventricles time to fill with blood from the atria before contracting. This delay is crucial for efficient heart function.
• Conduction System of the Heart

  • SA Node: Located in the right atrium, it initiates electrical impulses that start the heartbeat.
  • AV Node: It delays the impulse slightly to allow the ventricles to fill with blood.
  • Bundle of His: It carries the impulse from the AV node down the interventricular septum.
  • Bundle Branches: The Bundle of His splits into the right and left bundle branches.
  • Purkinje Fibers: These fibers spread throughout the ventricular walls, distributing the impulse to the ventricular muscle cells, leading to ventricular contraction.
• Physiologic Properties of Electrical Cells

  Automaticity - ability to initiate impulse

  Excitability - respond to impulse

  Conductivity - transmit impulse
• Physiologic Properties of Electrical Cells

  Automaticity - initiate

  Excitability - respond

  Conductivity - transmit
• Heart Rate = beats per minute (contraction)

  Stroke Volume = amount of blood ejected per contraction . N: 70 ml

  Cardiac Output = amount of blood ejected per one minute contraction.
• Cardiac Output

  CO = heart rate x stroke volume

  • Normal: 4 to 6 L
• 1. Preload: Stretchability of ventricle at end diastole
  2. Afterload: resistance that heart must overcome to eject contents of left ventricle
  3. Contractility: force of cardiac muscle contraction