Cardiac Embryo 1

• Primordial heart and vascular system appear

  middle of the third week
• Heart starts to function

  beginning of 4th week
• Need for an efficient method of acquiring oxygen and nutrients from the maternal blood and disposing of carbon-di-oxide and waste products
• Establishment of cardiogenic field

  Cardiac progenitor cells from epiblast receive signals from the node to form the heart field. Cells migrate craniolaterally and reside in the splanchnic layer of mesoderm
• Heart lies on the right side of the thorax instead of the left
• Heart loops to the left instead of right
• It may coincide with situs inversus
• DEXTROCARDIA
• SITUS INVERSUS
• Development of the sinus venosus

  Receives venous blood from the right and left sinus horns. Receives blood from Vitelline (omphalo-mesentric) vein, Umbilical vein, Common cardinal vein. Later, the entrance of the sinus shifts to the right. Communication between the sinus and the atrium becomes narrow over time
• Development of right atrium

  Right half of the primitive atrium forms the rough part of the atrium. Body & right horn of sinus venosus form the smooth part of the atrium. Right half of AV canal forms the right AV orifice
• Formation of left atrium

  Left half of the primitive atrium forms the rough part of the atrium. Absorbed pulmonary veins form the smooth part of the atrium. Left half of AV canal forms the left AV orifice
• Formation of interatrial septum

  End of the fourth week, the primordial atrium is divided into right and left atria by the formation and subsequent modification and fusion of two septa: Septum primum, Septum secundum. Three foramina are formed: Ostium primum, Ostium secundum, Foramen ovale. Septum primum grows from the roof of the common atrium towards the endocardial cushion. Opening between the lower rim of the septum primum & the endocardial cushion is the ostium (foramen) primum. Extensions of the endocardial cushion grow along the edge of the septum primum, closing the ostium pri
• End of the fourth week

  The primordial atrium is divided into right and left atria by the formation and subsequent modification and fusion of two septa: Septum primum, Septum secundum
• Three foramina formed

  • Ostium primum
  • Ostium secundum
  • Foramen ovale
• Septum primum growth

  From the roof of the common atrium towards the endocardial cushion
• Opening between the lower rim of the septum primum & the endocardial cushion

  Ostium (foramen) primum
• Extensions of the endocardial cushion growth

  Along the edge of the septum primum, closing the ostium primum
• Cell death before closure is complete

  Produces perforations in the upper portion of the septum primum
• Perforations join to form an opening

  Ostium (foramen) secundum, ensuring free blood flow from the right to the left primitive atrium
• Appearance of septum secundum


  A new crescent-shaped fold called septum secundum appears
• Septum secundum growth

  Doesn’t grow completely and overlap the ostium secundum and converts into foramen ovale
• Pre-natal conditions
• Post-natal conditions
• Patent foramen ovale (PFO) is usually asymptomatic
• 10 – 15% with cardiac ultrasound have Patent foramen ovale (PFO)
• Common congenital heart anomaly is Atrial Septal Defect
• Clinically significant types of Atrial Septal Defect

  • Ostium secundum defect
  • Endocardial cushion defect with ostium primum defect
  • Common atrium
• Development of ventricles

  Right ventricle develops from proximal 1/3rd part of the bulbous cordis, Left ventricle from the primitive ventricle
• Development of outflow tract

  Septum formation in the Truncus arteriosus and Conus cordis
• Formation of aorticopulmonary septum

  Pairs of opposing cushions in the outflow tract fuse and twist around each other to form aorticopulmonary septum
• Development of interventricular septum

  Interventricular septum is divided into muscular and membranous part, develops from three sources: From the floor of the ventricles, the muscular interventricular septum develops upwards towards the endocardial cushion and fuses with it, Membranous interventricular septum – the fusion of endocardial cushion with bulbous septum
• Ventricular septal defect is the most common type of congenital heart defect
• Types of Ventricular Septal Defect

  • Membranous VSD (most common)
  • Muscular type
• Transposition of Great arteries and Persistent Truncus arteriosus are abnormalities in conotruncal regions
• Tetralogy of Fallot is the most common cyanotic congenital heart malformation
• Four classic malformations in Tetralogy of Fallot

  • Pulmonary stenosis
  • Ventricular septal defect
  • Overriding aorta (rightward displacement of the aorta)
  • Right ventricular hypertrophy
• Types of Atresia and Stenosis

  • Tricuspid atresia
  • Aortic valve stenosis
  • Pulmonary valve atresia
  • Pulmonary valve stenosis
• CELLS THAT GIVE RISE TO THE HEART

  •Splanchnic layer of lateral plate mesoderm

  Myoepicardial mantle

  Myocardium, Epicardium & Conducting tissue

  Angioblastic mesenchyme

  Endocardium

  
  

  •Somatic layer of lateral plate mesoderm

  •Parietal layer of Pericardium