Anatomy of the heart

• The heart

  • Located in the thorax between the lungs
  • Protected by ribs and sternum
  • Between ribs 2-5 to the left of the midline
  • Apex at 5th intercostal space in the midclavicular line
• Heart Anatomy

  
• • Left ventricle thicker due to greater pressure
  • Atria and ventricles are electrically separated via bands of fibrous connective tissue (fibrous skeleton of the heart). Encircles pulmonary trunk and aorta where valves are suspended from it.
  • Pectinate muscles = act in the power of contraction in both left and right atria
  • Muscle ridges = trabecular cannae
• The pericardium*Allows heart to pump without friction

  1. Fibrous pericardium (outermost layer):

  • Inelastic
  • made of dense connective tissue
  • Fuses inferiorly with the diaphragm and superiorly with great vessels
  • Prevents overfilling and anchors heart in position

  1. Serous pericardium

  • under fibrous pericardium
  • Composed of two layers with the pericardial cavity in between(pericardial fluid):
  • Parietal layer: lines inner surface of fibrous pericardium
  • Visceral layer (epicardium): adheres to heart surface
• Heart wall

  1. (outer) epicardium = visceral pericardium, fatty with blood vessels
  2. Myocardium: cardiac muscle, biggest layer
  3. Endocardium: lined with simple squamous epithelium
• Heart valves

  • One way to prevent backflow
  • Atrioventricular: tricuspid and bicuspid
  • Opened by blood flowing from atria to ventricles
  • Anchored by chordae tenidae to papillary muscles
  • Contraction of papillary muscles prevents eversion of the valves andbackflow into the atria
  • Semilunar: pulmonary and aortic
  • Guards entrances of aorta and pulmonary trunk
  • Opened by force as ventricles contract
• Coronary circulation

  • Receives 250 ml/min of blood
  • Blood delivered to myocardium during ventricular relaxation
  • Left coronary artery → anterior interventricular, circumflex
  • Right coronary artery → marginal arteries, posterior intraventricular
  • Posterior and anterior intraventricular meet to form an anastomosis
  • Coronary sinus drains the heart
  • The great middle and small cardiac veins drain into the coronary sinus located in the epicardium
  • Anterior cardiac veins drain into the right atrium
• Foetal circulation

  • O2 and nutrients from placenta via umbilical cord
  • Need to bypass non functional lungs and liver via 3 circulatory shortcuts:
  • Foramen ovale: connects the right and left atria, bypassing the right ventricle and pulmonary system
  • Ductus arteriosus: connects pulmonary trunk to arch of aorta, bypassing pulmonary system and left side of the heart
  • Ductus venosus: connects umbilical vein to inferior vena cava, bypassing the liver
• Changes at birth

  
• Changes to adulthood

  • Foramen ovale → fossa ovalis
  • Ductus arteriosus → ligamentum arteriosum
  • Ductus venosus → ligamentum venosum