Heart anatomy

• Dr Julie Townsend: 'Senior Lecturer, [e-mail]'
• Heart 1: Anatomy Animal Health and the Veterinary Profession, VETS10022
• Intended Learning Outcomes


  • Explain the topographical location of the heart including species differences
  • Describe the connective tissue skeleton of the heart
  • Outline the conduction system of the heart
  • Describe the external features of the heart
  • Describe the structure of the atria and ventricles
  • Describe the structure of the valves of the heart
  • Describe the coronary circulation to the heart and recognise key species differences
  • Outline the circulatory system in the fetus (i.e. the flow of blood, oxygenation, placenta, foramen ovale, ductus arteriosus, ductus venosus)
  • Describe the changes in the fetal circulation after birth
• Signposting: Introduction to cardiovascular system lecture (week 7)
• Signposting: Opportunity to consolidate knowledge in relevant practicals (weeks 9-11)
• Signposting: You will use this information in the following CBLs: Coughing cavalier week 9, Lethargic cockapoo week 10, The cat with ATE consolidation case week 12
• Mediastinum divisions


  • Middle ventral
  • Middle dorsal
  • Cranial
  • Caudal
• Mediastinum is a central compartment situated between right and left pleural cavities containing the heart, oesophagus, blood vessels, nerves, lymphatics & thymus. Walls are formed by parietal (mediastinal) pleura
• Location of the heart

  • Plate of fibrous connective tissue between atria and ventricles serves as electrical insulation between atria and ventricles
  • Fibrous rings support valves & provide site for muscle attachment
  • Ossa cordis
• Conduction system of heart

  1. Action potentials (APs) originate in the SA node and travel across the atrial wall to the AV node. The SA node is known as the pacemaker of the heart

  2. APs pass through the AV node and along the AV bundle

  3. AV bundle divides into R & L bundle branches; APs reach apex of heart along these

  4. APs carried by purkinje fibres to ventricle walls
• External anatomy – left side

  • Cranial Vena Cava
  • Aorta
  • Caudal Vena Cava
  • Right Auricle
  • Right Ventricle
  • Left Ventricle
  • Apex
  • Right Atrium
  • Pulmonary Veins
• External anatomy – right side

  • Right Atrium: Intervenous tubercle, Fossa ovalis (remains of foramen ovale), Fibrous ring supports valve, Cusps are folds of endocardium, RAV – 3 cusps (tricuspid)
• Anatomical structures of the heart

  • Right Ventricle
  • Left Ventricle
  • Apex
  • Right Atrium
  • Pulmonary Veins
• External anatomy - right side

  • Right Atrium
• Right Atrium


  • Intervenous tubercle
  • Fossa ovalis (remains of foramen ovale)
  • Fibrous ring supports valve
  • Cusps are folds of endocardium
  • RAV - 3 cusps (tricuspid)
  • Chordae tendinae attach to free edges of cusp and papillary muscles
  • Arrangement prevents eversion of cusps back into atrium during systole
• Atrio-ventricular valves


  • Right Ventricle
• Right Ventricle


  • Conus arteriosus - cone-shaped exit leading to pulmonary trunk
  • Trabeculae carnae - muscular ridges on ventricle walls
  • Trabeculae septomarginalis – short cut for APs
  • Blood exits into pulmonary trunk via pulmonary valve – semilunar valve (3 cusps, but not called tricuspid!)
  • Receives Pulmonary veins
  • Auricle with pectinate muscle
  • Fossa ovalis
• Left Atrio-ventricular valve

  • Left Atrium
• Left Atrium


  • Thick walls
  • 2 papillary muscles
  • Trabeculae carnae
  • Aortic Valve
• Left Ventricle


  • Left Coronary Artery
  • Left interventricular / Paraconal branch
  • Circumflex branch
• Coronary arteries - LHS


  • Circumflex branch (of Left Coronary Artery)
  • Right Interventricular / Subsinuosal Branch
  • Right Coronary Artery
• Coronary arteries - RHS

  • Great Cardiac Vein
• Coronary Veins - LHS

  • Great Cardiac Vein
  • Coronary Sinus
  • Middle Cardiac Vein
• Coronary Veins - RHS

  • Great Cardiac Vein
• Fetal structures


  • Ductus venosus
  • Foramen ovale
  • Ductus arteriosus
• In the fetus: Caudal vena cava carries oxygenated blood, Pulmonary circulation and lungs not functioning, Pressure greater in RHS heart than left
• Fetal circulation: Lungs inflate, pulmonary circulation starts working, Placenta lost, umbilical vein regresses, Greater pressure in LHS heart than RHS, Valve of foramen ovale closes → fossa ovalis, Ductus arteriosus closes → ligamentum arteriosum
• After birth: Placenta, Abdominal aorta, Lungs
• Intended Learning Outcomes


  • Explain the topographical location of the heart including species differences
  • Describe the connective tissue skeleton of the heart
  • Outline the conduction system of the heart
  • Describe the external features of the heart
  • Describe the structure of the atria and ventricles
  • Describe the structure of the valves of the heart
  • Describe the coronary circulation to the heart and recognise key species differences
  • Outline the circulatory system in the fetus (i.e. the flow of blood, oxygenation, placenta, foramen ovale, ductus arteriosus, ductus venosus)
  • Describe the changes in the fetal circulation after birth