UNSW Embryology

Development of the Cardiovascular System
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Introduction

The heart develops very early from cardiogenic mesoderm that originally lies above the cranial end of the developing neural tube. Enlargement of the cranial neural fold brings this region ventrally to its correct anatomical position. The original paired cardiac tubes fuse, with the "ventricular" primordia initially lying above the "atria". Growth of the cardiac tube flexes it into an "S-shape" tube, rotating the "ventricles" downward and pushing the "atria" upward. This is then followed by septation, a complex process which converts this simple tube into a four chambered heart. A key part of this process is the separation of cardiac outflow (truncus arteriosus) into a separate pulmonary and aortic arch outflow. During embryonic development there is extensive remodelling of the initially r/l symetrical cardiovascular system and a contribution from the neural crest to some vessels. Their are 3 aortic/venous circulatory systems: umbilical, embryonic and vitelline. The umbilical system is is lost at birth, the vitelline contributes to the portal system and the embryonic matures into the cardiovascular system.

At birth there is a complete change with activation of the pulmonary system (lungs) and eventual closure of the channel between r. and l. atria (foramen ovale).

The molecular mechanisms regulating cardiac development are still largely unknown. Development does appear to be an independent mechanism preceding both skeletal and smooth muscle development and using different regulatory mechanisms (not MyoD or myogenin).

Development of the Heart

Hand1 gene (also called Hxt, eHAND, Thing1) encodes a basic helix-loop-helix (bHLH) transcription factor needed for both placenta (trophoblast) and cardiac development (mouse). A knockout study showed abnormal looping and ventricular myocardial differentiation. (Riley etal, 1998)

References

About Notes

  • Lecture notes compiled and written by Dr Mark Hill.
  • Note Links to OMIM Entries are copies of originals for computers without internet access. Computers with internet access can directly access the database.

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Date Last Modified: 11/3/99
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