Heart

• The heart: HOLLOW MUSCULAR ORGAN situated in the mediastinum of the thoracic cavity, enclosed in the pericardium.

  • somewhat PYRAMIDAL IN SHAPE and placed obliquely behind the sternum and adjoining parts of costal cartilages so that 1/3 of the heart is to the right of median plane and 2/3 of the heart is to the left of the median plane.

  • 4 chambers: right atrium and right ventricle, and left atrium and left ventricle.

  • On surface the atria are separated from the ventricles by the atrioventricular groove (aka coronary sulcus) and ventricles from each other by interventricular grooves.
• • The pericardium is a double-layered sac that surrounds and protects the heart.
  • consists of two layers: the outer fibrous pericardium and the inner serous pericardium

  
• Fibrous pericardium

  • forms boundaries of the middle mediastinum .
  • Shape : conical having a base, an apex and four surf

  1)Base: directed downwards and fussed with central tendon of diaphragm.

  2) Apex: directed upwards, fuse with adventitia of big vessels arising from heart .

  3) Post suf: related to oesophagus and descending aorta.

  4) Ant surf: connected to body of sternum by superior and inferior sternopericardial ligaments.

  5) 2 lateral surfaces: related to the corresponding lung, pleura and phrenic nerve

  
• Serous pericardium

  thin, double-layered membrane that forms a closed sac around the heart.

  • Viceral layer (epicardium of heart): covers outer surface of heart and roots of the great vessels. Arrange in form of 2 tube. Venous tube encloses superior, inferior vena cava, and pulmonary veins at venous end of heart. Arterial tube encloses aorta and pulmonary trunk at arterial end of heart tube.
  • Parietal layer: lines the inner surface of fibrous pericardium.

  pericardial cavity is found between the visceral and parietal layers and contains thin film of fluid to facilitate movements of the heart.

  
• • Visceral layer of serous pericardium is pain insensitive
  • Autonomic innervation by cardiac plexus, sympathetic and parasympathetic (vagus n)
  • develops from splanchnipleuric mesoderm
• • Fibrous pericardium + parietal layer of serous pericardium are pain sensitive
  • Pain is referred as supraclavicular region of shoulder of lateral to neck area
  • Somatic innervation ( phrenic nerve)
  • Somatopleuritic mesoderm
• • The fibrous pericardium and the parietal layer of serous pericardium: supplied by sensory fibers from the phrenic nerve

  The visceral layer of serous pericardium: is supplied by autonomic fibers (parasympathetic through the vagus and sympathetic fibers from the cardiac plexuses)
• The serous pericardium, includes certain anatomical features known as pericardial sinuses.

  • These sinuses are recesses /spaces within the pericardial cavity created by the folding of the serous pericardium around the great vessels.
  • The two main pericardial sinuses are the transverse pericardial sinus and the oblique pericardial sinus.
• Transverse sinus

  • This sinus is located posterior to the ascending aorta and the pulmonary trunk, and anterior to the superior vena cava and the atria.
  • It is a short passage that runs transversely across the heart.
  • The transverse pericardial sinus is formed by the reflection of the serous pericardium around the great arteries (aorta and pulmonary trunk) and veins (superior vena cava, left atrium).

  
• Oblique sinus

  • is a cul-de-sac located posterior to the heart.
  • It lies behind the left atrium and is bordered by the pulmonary veins and inferior vena cava
  • The oblique pericardial sinus is formed by the reflection of the serous pericardium around the pulmonary veins and inferior vena cava.

  It is a blind-ended pocket that extends upwards behind the left atrium

  
• Heart: definition, location

  • The heart is a cone-shaped, muscular organ about the size of a closed fist, weighing approximately 250-350 grams
  • located in thoracic cavity within the mediastinum, between the lungs, slightly left of the midline. Its orientation is such that the base points towards the right shoulder and the apex points towards the left hip.

  
• Surfaces of the Heart

  Heart has a base, apex and 3 surfaces:

  Base: faces posteriorly towards the vertebral column.

  • Anterior (Sternocostal) Surface: Lies directly behind the sternum and costal cartilages
  • Inferior (Diaphragmatic) Surface: Rests on the diaphragm
  • Right Pulmonary Surface: faces right lung
  • Left pulmonary surface: faces left lung

  
• External Landmarks and Sulci heart

  1. Coronary Sulcus (Atrioventricular ):Encircles heart at junction of atria and ventricles. Contains right and left coronary artery coronary sinus, and cardiac veins. Marks the separation between atria and ventricles
  2. Interatrial sulci (ant + post): on post aspect. Not well defined
  3. Anterior Inter-ventricular sulci:Runs along the anterior surface of heart. Contains anterior interventricular artery and great cardiac vein.
  4. Posterior interventricular sulci: Runs along posterior surface of heart. Contains posterior interventricular artery and the middle cardiac vein

  
• Apex and base of heart

  • Apex: formed entirely by left ventricle. Located in adults at left 5th intercostal space approximately 9cm midsternal line. In children in left 4th intercostal space.
  • Base (aka posterior surface): former by 2/3 of left atrium + 1/3 of right atrium. Most fixed part of heart. Where the great vessels (aorta, pulmonary veins, superior and inferior vena cava) enter and leave the heart.
• Topography and relations of heart

  • Anteriorly: Related to the sternum, costal cartilages, and anterior ends of the ribs.
  • Posteriorly: Related to the esophagus, descending aorta, and thoracic vertebrae.
  • Laterally: Related to the lungs and pleura.
  • Inferiorly: Related to the diaphragm.

  
• Borders of heart

  • Right Border: formed by right atrium
  • Left border: formed by left auricle and left ventricle
  • Superior border: The right and left atria and the great vessels
  • Inferior border:formed by right ventricle and a small part of the left ventricle. Rests on diaphragm