Development of the Heart - Anatomy and Physiology 2e

Learning Objectives

• Describe embryological development of heart structures.
• Identify five regions of the fetal heart.
• Relate fetal heart structures to adult counterparts.

Introduction

• The heart is the first functional organ to develop in a human.
• It begins beating and pumping blood around day 21 or 22 after fertilization.
• The heart is crucial for distributing blood and exchanging nutrients, oxygen, and wastes.
• Development begins with a noticeable heart bulge on the embryo's anterior surface.

Embryological Development

• The heart forms from mesoderm, one of the three primary germ layers, 18-19 days post-fertilization.
• Development initiates in the cardiogenic area located near the embryo's head.
• Signals from the endoderm trigger the formation of cardiogenic cords.
• Cardiogenic cords develop into endocardial tubes, which fuse to form a primitive heart tube.

Primitive Heart Tube Regions

1. Truncus Arteriosus
   • Develops into ascending aorta and pulmonary trunk.
2. Bulbus Cordis
   • Forms the right ventricle.
3. Primitive Ventricle
   • Becomes the left ventricle.
4. Primitive Atrium
   • Transforms into anterior portions of both right and left atria, and the auricles.
5. Sinus Venosus
   • Evolves into the posterior right atrium, SA node, and coronary sinus.

Heart Development Process

• The elongation of the heart tube leads to folding into an S shape, forming the basic layout of adult heart chambers and vessels.
• Partitioning of atria and ventricles occurs through the development of septa:
  • Interatrial septum
  • Interventricular septum
  • Atrioventricular septum
• Atrioventricular valves form between weeks 5 and 8.
• Semilunar valves form between weeks 5 and 9.
• Fetal blood shunts remain until birth or shortly after.

Conclusion

• The development of the heart is a complex process involving transformations in structure and function, preparing the fetus for independent life post-birth.