Venous system

• The embryo has three major primitive venous systems that fulfil different function:

  • vitelline system
  • Umbilical system
  • cardinal system
• vitelline system function → drains the gastrointestinal tract and its derivatives
• Umbilical system function → carries oxygenated blood from the placenta to the embryo
• Cardinal system function → drains the head, neck and body wall
• The three systems are initially bilaterally symmetric, leading blood towards the right and left horns of the sinus venosus (the inflow end of the developing heart).
• Trigger of remodeling of the three primitive venous systems to reshape them to yield the adult patterns → the venous blood flow is redirected to the right atrium only