Embryology of the Heart Development

Cardiogenic Area and Heart Formation

• The cardiogenic area is induced by pharyngeal endoderm underlying the primary heart field.
• Horseshoe-shaped blood islands form from angiogenic clusters, leading to the creation of endothelial-lined heart tubes.
• These tubes are surrounded by myoblasts, integral for heart muscle development.

Dorsal Aortae Development

• Bilateral blood islands near the midline or paranotochordal region contribute to the formation of dorsal aortae.
• The heart derives from angioblastic tissue emerging from the splanchnopleuric mesoderm.

Cardiac Progenitor Cells

• Cardiac progenitor cells appear in the caudal epiblast lateral to the primitive streak during the 16th to 18th days of development.
• These cells migrate cranially through the primitive streak into the splanchnopleuric layer, establishing a horseshoe-shaped primary heart field.

Heart Field Specification

• The primary heart field is formed at the cranial end of the embryonic disc, rostral to the buccopharyngeal membrane.
• Laterality sequencing leads to the organization of cardiac progenitor cells into specific regions: atria, left ventricle, and part of the right ventricle.

Molecular Mechanisms of Laterality

• The accumulation of signaling molecules (serotonin, nodal, and FGF8) distinguishes left-sided cardiac development.
• On the right side, monoamine oxidase (MAO) influences development.
• PITX2 is identified as the master gene determining left-sided structures.

Heart Tube Structure

• Initially, right and left endothelial heart tubes form and subsequently fuse.
• The single heart tube exhibits dilatations:
  • Bulbus cordis
  • Primitive ventricle
  • Primitive atrium (atrium)
  • Sinus venosus

Connections within Heart Tube

• Sinus venosus and atrium are linked by the sinoatrial orifice.
• The atrium communicates with the ventricle via the atrioventricular (AV) canal.

Cardiac Septation

• Definitive heart septations occur between the 5th and 8th weeks of development.
• Development of all heart chambers occurs simultaneously, though can be discussed separately for clarity.

Sinus Venosus and Right Atrium

• The sinus venosus is the caudal-most part of the primitive heart tube, with significant absorption into the right atrium.

This quiz covers the embryological development of the heart, focusing on the formation of cardiogenic areas, blood islands, heart tubes, and the role of splanchnopleuric mesoderm. It also includes details about the formation of dorsal aortae and the underlying primary heart field.