19.5 Development of the Heart - Anatomy and Physiology 2e | OpenStax

Learning Objectives

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

Key Points

• First Functional Organ: The human heart is the first functional organ to develop, starting to beat and pump blood around day 21 or 22 after fertilization.
• Embryonic Tissue: The heart forms from mesoderm, one of the three primary germ layers, around 18-19 days post-fertilization.
• Cardiogenic Area: Heart development begins in the cardiogenic area near the embryo's head.
• Cardiogenic Cords: Formation begins with the cardiogenic cords, which develop into endocardial tubes, fusing into a single primitive heart tube.

Primitive Heart Tube

• Regions: The primitive heart tube forms five regions:
  • Truncus arteriosus
  • Bulbus cordis
  • Primitive ventricle
  • Primitive atrium
  • Sinus venosus
• Blood Flow: Initially, blood flows from the sinus venosus to the truncus arteriosus.

Development Stages

• Truncus Arteriosus: Divides to form the ascending aorta and pulmonary trunk.
• Bulbus Cordis: Develops into the right ventricle.
• Primitive Ventricle: Forms the left ventricle.
• Primitive Atrium: Becomes anterior portions of both right and left atria, and auricles.
• Sinus Venosus: Develops into the posterior right atrium, SA node, and coronary sinus.

Heart Folding and Chamber Formation

• Folding Process: The heart tube elongates and folds, forming an S-shape, aligning chambers and vessels akin to the adult heart (Days 23-28).
• Septal and Valve Development:
  • Septa (interatrial, interventricular, atrioventricular) complete by the fifth week.
  • Atrioventricular valves form between weeks 5-8.
  • Semilunar valves form between weeks 5-9.

Summary

The heart's development is a complex, early embryological process, involving formation from the mesoderm, initial blood flow patterns, and transformation of primitive structures into the mature heart components. This development is crucial for establishing effective circulation and nutrient exchange for the growing embryo.