During cardiogenesis, the primary heart tube is initially formed by which embryonic structure?

• A Somatic mesoderm of the pericardial cavity
• B Cardiac neural crest cells migrating from rhombomeres 6–8
• C Splanchnic mesoderm of the cardiogenic crescent (first heart field) ✓
• D Secondary heart field derived from pharyngeal mesoderm

Explanation

The primary heart tube is formed by fusion of bilateral endocardial tubes derived from the splanchnic (visceral) mesoderm of the cardiogenic crescent — also called the first heart field. These cells form the left ventricle and parts of the atria. The second heart field (pharyngeal mesoderm) contributes to the right ventricle, outflow tract, and the remainder of the atria, elongating the primary tube. Cardiac neural crest cells contribute to the aortopulmonary septum (outflow septation) but not the primary tube itself.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.