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The heart

  • Situated in the middle mediastinum
  • Lies freely within the pericardium
  • Pyramidal in shape
  • Base lies posteriorly
  • Apex is anterioinferior and points to left
  • Three surfaces
    • Strenocostal - formed by right atrium and ventricle and partly by left ventricle and atrium
    • Diaphragmatic - formed by right and left ventricles
    • Base - formed by left atrium, to a lesser extent by the right atrium
  • Connected to the great vessels at the base
  • Atrioventricular groove - separates the right and left atrium from the ventricles
  • Anterior and posterior interventricular grooves join each other
  • Important relations of the heart included
  • Laterally
    • Phrenic nerves. Run adjacent to the pericardium
  • Posteriorly
    • Posterior mediastinal structures
    • Oesophagus- behind the left atrium
    • Descending thoracic aorta on left side
    • Azygos vein on the right side
    • Thoracic duct

Blood supply

Left coronary artery

  • Arises from left posterior aortic sinus
  • Passes behind the pulmonary trunk and then lies under the left auricle
  • Divides into anterior interventricular and circumflex branches

Anterior interventricular artery

  • Also known as left anterior descending artery
  • Continues in the anterior interventricular groove
  • Anastomoses with the posterior interventricular branch of the right coronary artery
  • Gives the diagonal branch

Circumflex artery

  • Winds (circumflexes) around the left heart border
  • Passes in the atrioventricular groove
  • Anastomoses with the right coronary artery Right coronary artery
  • Arises from anterior aortic sinus
  • Passes between the pulmonary trunk and the right atrium
  • Traverses the atrioventricular groove
  • Ends by anastomosing with the branches of circumflex artery
  • Branches include
    • To the sino-atrial node
    • To left atrium
    • Right marginal artery
    • Posterior interventricular artery (also known as posterior descending artery)

 “Dominance” of the coronary circulation

  • Right dominance
    • Posterior interventricular artery arises from the right coronary artery
  • Left dominance
    • Posterior interventricular artery arises from left coronary artery (10%)
  • Codominant
    • Posterior interventricular artery formed by both right and left coronary arteries (10%)

Blood supply to the conducting system of the heart

  • SA node - branch from right coronary artery in 60% of the population
  • AV node - from posterior interventricular artery

Venous drainage

Coronary sinus

  • Receives most of the blood
  • Lies in the posterior part of the atrioventricular groove
  • Opens into the right atrium
  • Is a continuation of the great cardiac vein
  • Tributaries included middle and small cardiac vein

Anterior cardiac vein

  • Open directly into the right atrium Venae cordae minimae
  • Drain directly into the chambers of the heart

Nerve supply of the heart

  • Sympathetic
    • Cervical and upper thoracic portions of the sympathetic chain through the stellate ganglion
    • Afferent fibres running with the sympathetic fibres conduct pain
  • Parasympathetic
    • Vagus nerves
  • The sympathetic and parasympathetic nerves form cardiac plexuses
  • Superficial cardiac plexus lies in front of the right pulmonary artery
  • Deep cardiac plexus lies in front of the tracheal bifurcation

Pericardium

  • Fibro-serous layer enclosing the heart and roots of great vessels
  • Outer fibrous
  • Inner serous is as double layered
  • Has inner visceral layer and outer parietal layer
  • Both layers continuous around the great vessels and the pulmonary veins
  • This leads to the formation of the pericardial sinuses

Pericardial sinuses

  • Two in number - oblique sinus and transverse sinus
  • Lie on the posterior surface of the heart

Author:  Dr Shakeeb Khan

 

 
 

Last updated: 05 January 2008

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