ANATOMY

• location of pericardium


  The pericardium lies within the middle mediastinum, posterior to body of sternum and 2nd–6th costal cartilages and anterior to T5-T8 vertebrae.
• layers of pericardium


  (a) Outer single layered fibrous sac called fibrous pericardium (b) Inner double layered serous sac called serous pericardium.
• -Formed of strong fibrous tissue, below it blends with central tendon of diaphragm.

  -It is cone shaped with blunt apex upwards and base downwards.

  -Its apex lies at the level of sternal angle, fused with the outer tunica adventitia of great blood vessels that pass through it (ascending aorta, pulmonary trunk, superior vena cava).

  -Function: Anchors the heart & keeps the heart in position, minimize friction during movement of heart and prevents over distension of heart.


  Fibrous pericardium

  
• Serous pericardium


  Forms the inner lining to the fibrous pericardium which covers the heart and great vessels
• Serous pericardium


  • Composed of two layers: Parietal and visceral layers
• Parietal layer of serous pericardium


  Lines the inner aspect of fibrous pericardium and is reflected around the roots of great blood vessels to become continuous with the visceral layer
• Visceral layer of serous pericardium (Epicardium)


  Closely applied to the heart (myocardium) and is also called as the epicardium
• Pericardial cavity


  The space between the parietal and visceral layers of serous pericardium
• The pericardial cavity contains a small amount of serous pericardial fluid about 15 -50 ml, which acts as a lubricant to facilitate the movements of heart
• pericardial sinuses


  Pericardial sinuses were formed due to reflection of visceral layer of serous pericardium around great vessels of heart.

  
• -lies between the reflection of serous pericardium around the aorta and reflection around large veins.

  -Located between the aorta and pulmonary trunk anteriorly and superior vena cava posteriorly.

  -Boundaries: Anteriorly: Ascending aorta and pulmonary trunk.

  Posteriorly: Superior vena cava.

  Superiorly: Bifurcation of the pulmonary trunk

  Inferiorly: Upper part of left atrium

  Laterally: Opens into the general pericardial cavity.

  transverse sinus
• Locating transverse sinus

  when the pericardium is opened during surgery, a finger passed behind pulmonary trunk & ascending aorta enters into the transverse sinus

  
• Space


  Lies behind the left atrium
• Space


  • Inverted J-shaped reflection of visceral layer of serous pericardium
  • Encloses six veins (2 vena cavae and 4 pulmonary veins)
  • Allows proper filling of the left atrium
• Boundaries of the space

  • Anteriorly: Left atrium
  • Posteriorly: Parietal pericardium & fibrous pericardium
  • Right lateral: Right pulmonary veins and inferior vena cava
  • Left lateral: Left pulmonary veins
  • Superiorly: Visceral pericardial reflection along right & left superior pulmonary veins
  • Inferiorly: Open space
• Locating oblique sinus


  A hand placed under the apex of the heart & moved superiorly will slip into the oblique sinus.
• arterial supply of pericardium-Fibrous & parietal layer of serous pericardium are supplied by

  -Fibrous & parietal layer of serous pericardium are supplied by

   Pericardial branches of internal thoracic artery.

   Pericardiacophrenic artery.

   Musculophrenic artery.

   Posterior intercostal arteries.

   Branches from descending thoracic aorta.

  
  

  -Visceral layer of serous pericardium is supplied by right and left coronary arteries
• Pericadial veins drain into

   Azygos vein.

   Internal thoracic vein.  Coronary sinus.
• Nerve supply of the pericardium:

  -Fibrous pericardium and the parietal layer of serous pericardium: Pain sensitive. Supplied by phrenic nerves, intercostal nerves.

  -Visceral layer of serous pericardium: Pain insensitive. Innervated by branches of sympathetic trunk and vagus nerves through superficial and deep cardiac plexus.
• Pericarditis


  Inflammation of the pericardium is called pericarditis
• Pericardial effusion: 


  Pericarditis causes excessive accumulation of serous fluid in the pericardial cavity, which is referred as pericardial effusion
• Cardiac tamponade


  -Compression of the heart caused by pericardial effusion.

  -Compression does not allow full expansion of the heart, resulting in reduced ventricular filling which in turn reduces cardiac output.

  -It may occur after trauma (stab or gunshot wounds), cardiac surgery & pericarditis
• Procedure done to relieve cardiac tamponade. A procedure to remove the excessive pericardial fluid from the pericardial cavity by two routes of approach- either by sternal approach or Subxiphoid approach

  Pericardiocentesis
• Histology of cardiac muscle

  
• Compare and contrast skeletal muscle from cardiac muscle

  
• Tunica intima of large artery


  • Thicker than in the muscular arteries
  • Shows endothelium and subendothelial connective tissue
  • Endothelial cells line the lumen
  • Internal elastic lamina is similar to the elastic lamina of the next layer tunica media, hence not seen clearly
• Tunica media of large artery


  • Consists of more amount of concentrically arranged elastic fibres
  • Few amount of smooth muscle cells and collagen fibres
  • External elastic lamina not seen clearly
• Tunica adventitia of large artery


  • Composed of fibroelastic connective tissue with small blood vessels called vaso vasorum and nerve fibres
• •Tunica intima: single layer of endothelial cells and a very thin subendothelial layer of loose connective tissue. Internal elastic lamina prominently seen.

  • Tunica media: intermingled with elastic lamellae. External elastic lamina seen clearly.

  • Tunica adventitia: consists of connective tissue. Lymphatic capillaries, vasa vasorum, and nerves are also found in the adventitia and these structures may penetrate to the outer part of the media.


  Histology of Medium sized artery

  
• Arteriosclerosis


  elastin fibers in the arteries loses the elasticity & the structured arrangement of elastin fibers is lost, as a result, the arterial wall becomes stiff & hard
• Atherosclerosis


  -Type of arteriosclerosis, in which the wall of arteries become narrow due to a buildup of plaque.

  -Degenerative changes are seldom seen in small arteries.
• Acute aortic syndrome


   Aortic dissection

   Penetrating aortic ulcer

   Intramural haematoma.
• Aortic dissection


  Aortic dissections from the initial intimal tear can progress distally, proximally, or in both directions from the point of origin.

  Anterograde dissections propagate towards the iliac arteries and retrograde dissections propagate towards the aortic valve (at the root of the aorta)
• -Tunica intima: Shows endothelium and subendothelial connective tissue.  -Tunica media: Is thin than the adventia, composed of elastic fibres, smooth muscle and collagen fibres. Abundant connective tissue.

  -Tunica adventitia: • Thickest and well developed. • Contains fibroelastic connective tissue and longitudinal bundles of smooth muscle.


  Histology of Large Vein

  
• Heart

  Consists of four chambers - right atrium, right ventricle, left atrium and left ventricle
• Chambers of the heart

  1. Right & left atria separated by interatrial septum

  2. Right & left ventricles separated by interventricular septum
• Atrium


  Communicates with corresponding ventricle through atrioventricular orifice
• Right atrium


  Communicates with the right ventricle through right atrioventricular orifice, which is guarded by tricuspid valve
• Left atrium


  Communicates with the left ventricle through the left atrioventricular orifice, which is guarded by bicuspid valve/mitral valve
• Atria and ventricles


  • Separated on the surface by the atrioventricular groove (also called coronary sulcus)
  • Ventricles separated from each other by interventricular grooves