Development of Ventricles and Outflow Tracts

Introduction

• Topic: Development of ventricles and outflow tracts in the heart
• Challenges: Difficulty in understanding and learning this topic
• Goal: Simplification for easier understanding

Heart Structures

• Ventricles: Right and left separated by interventricular septum
  • Muscular portion (below)
  • Membranous portion (above)
• Inflowing Part: Rough due to trabeculae carneae and papillary muscles
• Outflowing Part: Smooth, includes:
  • Infundibulum or conus arteriosus (right)
  • Aortic vestibule (left)
• Vessels:
  • Pulmonary trunk (right)
  • Aorta (left)

Heart Tube Development

• Heart Tube Components: Sinus venosus, Primitive Atrium, Primitive Ventricle, Bulbus Cordis, Truncus Arteriosus
• Heart Looping: Atria and sinus venosus move upwards/backwards, others move forwards/downwards

Focus Areas

• Truncus Arteriosus
• Bulbus Cordis:
  • Distal third is Truncus Arteriosus
  • Middle third is Conus Cordis
  • Proximal third contributes to trabeculated part of right ventricle

Development of Outflow Tracts

• Structures Involved:
  • Truncus Arteriosus
  • Conus Cordis
• Spiral Septum: aka Conotruncal or Aorticopulmonary septum
• Formation Process:
  • Truncus Arteriosus develops truncal swellings/ridges with neural crest cell contribution
  • Conus develops ridges that fuse with truncal swellings
  • Formation of spiral septum separates and spirals the aorta and pulmonary trunk

Formation of Ventricles

• Bulbus Cordis: Proximal third forms trabeculated part of right ventricle
• Primitive Ventricle: Forms left ventricle
• Bulboventricular Sulcus: Site of communication between chambers, known as primary interventricular foramen

Separation of Ventricles

• Interventricular Septum:
  • Muscular growth from apex
  • Leaves interventricular foramen to be closed by membranous part
• Membranous Part Formation:
  • Fusion of aorticopulmonary septum with truncal and bulbar ridges
  • Atrioventricular cushion proliferation closes the gap

Semilunar Valves Development

• Neural Crest Cells: Form valvular swellings
• Valve Formation:
  • Swellings at Truncus Arteriosus and Conus Cordis junction
  • Formation of 3 cusps each for aortic and pulmonary valves

Summary

• Right and left ventricles have separate outflow tracts
• Pulmonary trunk and ascending aorta established
• Semilunar valves formed with 3 cusps each

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