THE HEART

The Heart

Components of the Cardiovascular System
  • Blood Vessels:
    • Arteries: Carry blood away from the heart.
    • Veins: Carry blood toward the heart.
  • Pulmonary Circuit: Directs blood to the lungs for oxygenation.
  • Systemic Circuit: Distributes oxygenated blood to the organs and tissues of the body, including heart and lung wall tissues.
Location of the Heart
  • Base: Found at the inferior border of the second rib.
  • Apex: Rests on the diaphragm, positioned between the 5th and 6th ribs.
  • The heart tilts slightly to the left and anteriorly.
Pericardial Membranes and Heart Wall
  • Pericardial Membranes:
    • Fibrous Pericardium
    • Serous Pericardium: Divided into parietal and visceral layers.
  • Heart Wall Layers:
    • Myocardium: Thick, muscular middle layer.
    • Endocardium: Inner lining of the heart.
Anatomy of the Heart
  • Major vessels associated with the heart include:
    • Superior vena cava
    • Inferior vena cava
    • Aorta (ascending and descending)
    • Pulmonary trunk
    • Pulmonary veins
Atria and Their Features
  • Right Atrium:
    • Contains auricle, smooth wall (posterior), pectinate muscles, coronary sinus, openings for IVC and SVC.
    • Right AV valve (tricuspid valve)
  • Left Atrium:
    • Contains auricle, mostly smooth with pectinate muscle.
    • Left AV valve (bicuspid or mitral valve)
Ventricles and Their Features
  • Right Ventricle:
    • Contains trabeculae carneae, papillary muscles, chordae tendineae.
  • Left Ventricle:
    • Thicker wall than the right ventricle, responsible for systemic circulation.
Heart Valves
  • Atrioventricular Valves:
    • Tricuspid Valve: Between right atrium and ventricle.
    • Mitral Valve: Between left atrium and ventricle.
  • Semilunar Valves:
    • Pulmonary Valve: Between right ventricle and pulmonary trunk.
    • Aortic Valve: Between left ventricle and aorta.
Coronary Circulation
  • Cardiac Vessels:
    • Coronary Arteries: Supply oxygen-rich blood to the heart muscle.
    • Coronary Veins: Carry deoxygenated blood away from the heart muscle.
Blood Flow Through the Heart
  1. Blood returns from body through SVC/IVC.
  2. Blood enters right atrium and flows to right ventricle through tricuspid valve.
  3. Right ventricle pumps blood to lungs via pulmonary semilunar valve and pulmonary trunk.
  4. Oxygenated blood returns from lungs to left atrium via pulmonary veins.
  5. Blood flows to left ventricle through mitral valve.
  6. Left ventricle pumps blood to body through aortic semilunar valve into aorta.
Heart Sound Mechanics ("Lubb-Dupp")
  • Lubb: Closure of atrioventricular valves during ventricular contraction.
  • Dupp: Closure of semilunar valves during ventricular relaxation.
  • Listening Points:
    • Aortic valve: 2nd intercostal space (right sternal margin).
    • Pulmonary valve: 2nd intercostal space (left sternal margin).
    • Mitral valve: Over heart apex (5th intercostal space).
    • Tricuspid valve: Right sternal margin of 5th intercostal space.
Conductive System of the Heart
  • Components:
    • Sinoatrial Node (SA): Pacemaker of the heart.
    • Atrioventricular Node (AV): Delays impulse for ventricle filling.
    • Bundle of His and Purkinje Fibers: Distribute signals for ventricular contraction.
  • Normal Heart Rate: Approximately 72 beats per minute (bpm).
Fetal Circulation
  • Foramen Ovale: Allows blood to pass from right to left atrium, bypassing the lungs.
  • Ductus Arteriosus: Connection between pulmonary trunk and aorta, also facilitating bypass.
Birth Changes in Circulation
  • Prostaglandin Drop: Triggers physiological changes leading to circulation adaptation.
  • Closure of Foramen Ovale and Ductus Arteriosus: Transitions from fetal to postnatal circulation.
Conditions Affecting Circulation
  • Patent Ductus Arteriosus (PDA): Left to right shunt causes repeated blood flow to pulmonary circuit, leading to ventricular hypertrophy and cyanosis in infants.