A scanning electron microscopic study of the ferret atrioventricular node

Area of Science:

• Cardiovascular Biology
• Cellular Morphology
• Cardiac Electrophysiology

Background:

• The atrioventricular (AV) node is critical for regulating heart rhythm.
• Understanding the cellular architecture of the AV node is essential for explaining cardiac impulse conduction and delays.

Purpose of the Study:

• To investigate the three-dimensional morphology of ferret AV nodal and transitional zone cells.
• To elucidate the relationship between cell shape, intercellular contacts, and AV nodal function.

Main Methods:

• Scanning electron microscopy (SEM) was employed to visualize the ferret heart's AV node and surrounding transitional zone.
• Detailed examination of cell shape, size, and the nature of cell-to-cell appositions.

Main Results:

• Transitional cells are cylindrical with extensive branching, forming numerous contacts with adjacent cells.
• Superficial AV nodal cells are smaller and fusiform, with contacts primarily via overlapping end processes.
• Deep AV nodal cells are slightly larger than superficial ones and exhibit more intercellular contacts.

Conclusions:

• Cellular morphology and intercellular relationships in the ferret AV node are distinct between cell types.
• These structural characteristics likely play a significant role in mediating atrioventricular impulse propagation and the characteristic AV nodal delay.