heart and pericardium

• Heart


  • Located in the middle mediastinum within the pericardium
  • About the size of a fist and weighs 250-300 g
• Position of the heart in the thorax

  • Placed obliquely in the middle mediastinum
  • Approximately two-thirds of the heart lies to the left and one-third to the right of the midline
  • The shape of the heart is that of a pyramid that is resting on one of its sides
• External morphology of the heart

  • Apex
  • Base
  • Four borders: Right, inferior, left and superior
  • Two surfaces: Sternocostal (anterior) and diaphragmatic (inferior)
  • Four grooves: Interatrial, atrioventricular, anterior and posterior interventricular
• Apex


  Formed by the left ventricle, directed downwards, forwards & to the left
• Base


  Mainly formed by the left atrium, directed backwards
• Sternocostal surface


  • Atrial part: Right atrium (mainly), Left auricle (small part)
  • Ventricular part: Right ventricle (2/3), Left ventricle (1/3)
  • Separated by anterior interventricular groove containing anterior interventricular artery and great cardiac vein
• Diaphragmatic surface


  • Left ventricle (2/3), Right ventricle (1/3)
  • Separated by posterior interventricular groove containing posterior interventricular artery and middle cardiac vein
  • Separated from the base by atrioventricular (coronary) groove containing anastomosis between right coronary and circumflex arteries, and coronary sinus
• Borders of the heart

  • Right border: Right atrium
  • Inferior border: Mainly right ventricle, completed by apex of left ventricle
  • Left border: Mainly left ventricle, completed by left auricle
  • Superior border: Mainly left atrium, completed by right atrium
• Internal morphology of right atrium

  • Rough anterior part with pectinate muscles
  • Smooth posterior part (sinus venarum) with openings of SVC, IVC and coronary sinus
  • Rough and smooth parts separated by sulcus terminalis and crista terminalis
  • Interatrial septum has oval depression called fossa ovalis surrounded by annulus ovalis
• Openings of the right atrium

  • SVC
  • IVC
  • Coronary sinus
  • Anterior cardiac veins
  • Venae cordis minimi
  • Tricuspid valve
• Left atrium

  • Posterior wall receives the four pulmonary veins
  • Contains lunate fossa corresponding to fossa ovalis in interatrial septa
  • Interior is almost smooth except for the auricle
• Differences between right and left ventricles

  • Right ventricle: Thinner, semilunar outline, three papillary muscles, moderator band
  • Left ventricle: Thicker (3 times), circular outline, two papillary muscles, no moderator band
• Rough inflowing part of ventricles

  • Due to trabeculae carnae
• Smooth outflowing part of ventricles

  • Right ventricle: Infundibulum (conus arteriosus), separated from rough part by supraventricular crest
  • Left ventricle: Vestibule, no crest
• Inlet valves

  • Right ventricle: Tricuspid valve (anterior, posterior and septal cusps)
  • Left ventricle: Mitral valve (anterior and posterior cusps)
• Outlet valves


  • Right ventricle: Pulmonary valve (two anterior and one posterior cusps)
  • Left ventricle: Aortic valve (one anterior and two posterior cusps)
• Components of heart valves

  • Fibrous ring and cusps
  • Cusp has atrial and ventricular surfaces, attached to chordae tendinae
• The interventricular septum is formed of lower muscular and upper membranous parts
• Surface anatomy of the heart

  • Point a: Left 2nd costal cartilage 4 cm from midline
  • Point b: Right 3rd costal cartilage 3 cm from midline
  • Point c: Right 6th costal cartilage 3 cm from midline
  • Point d (apex): Left 5th intercostal space 9 cm from midline
• Surface anatomy of cardiac valves

  • Pulmonary valve: Left 3rd sternocostal junction
  • Aortic valve: Left 3rd intercostal space
  • Mitral valve: Left 4th sternocostal junction
  • Tricuspid valve: Midline of sternum opposite 4th intercostal space
• Auscultatory areas of cardiac valves

  • Pulmonary valve: Left 2nd sternocostal junction
  • Aortic valve: Right 2nd sternocostal junction
  • Mitral valve: Apex of the heart
  • Tricuspid valve: To the left of xiphisternal junction
• Pericardial effusion is usually removed by inserting a needle in the left 5th or 6th intercostal spaces close to the sternum to avoid piercing left lung and pleura
• Layers of pericardium


  • Fibrous pericardium: Strong external single layered fibrous sac
  • Serous pericardium: Internal double-layered sac
• Relations of fibrous pericardium

  • Apex: Surrounds ascending aorta, pulmonary trunk and SVC
  • Base: Fuses with central tendon of diaphragm, pierced by IVC
  • Anterior aspect: Covered by lungs and pleurae except bare area where pericardium contacts thoracic wall
  • Posterior aspect: Related to descending aorta and oesophagus
  • Lateral aspects: Related to phrenic nerves, pericardiophrenic vessels, lungs and pleurae
• Layers of serous pericardium

  • Parietal layer: Lines the fibrous pericardium
  • Visceral layer: Adherent to the heart forming its epicardium
• Blood supply of pericardium

  • Fibrous pericardium and parietal layer: Arterial supply from pericardiacophrenic artery, venous drainage through pericardiacophrenic veins and tributaries of azygos system
  • Visceral layer: Same as heart
• Nerve supply of pericardium

  • Fibrous and parietal layer: From phrenic nerves
  • Visceral layer: Autonomic from cardiac plexuses
• Pericardial sinuses

  • Transverse sinus: Anterior - ascending aorta and pulmonary trunk, Posterior - SVC and two atria
  • Oblique sinus: Anterior - back of left atrium, Posterior - parietal pericardium covering descending aorta and oesophagus, Superior - reflection of visceral to parietal pericardium, Inferior - opened and continuous with pericardial cavity, Right - two right pulmonary veins and IVC, Left - two left pulmonary veins