Pectinate Muscles Observed in an Anterior Section of the Right Atrium

Description

Anterior sectioning of the right atrium exposes the atrial lumen with the pectinate muscles (musculi pectinati) forming parallel, ridge-like bundles along the anterolateral wall and extending into the right auricle (atrial appendage). Medially, the smooth posterior wall of the atrium contrasts with the trabeculated auricular region, establishing the typical division between sinus venarum and the muscular atrium. The ridges run predominantly in a superoinferior direction as they course from the atrial wall toward the appendage. Clear regional contrast. Clinically, this distribution matters because the pectinate-rich right atrial appendage is a common substrate for macroreentrant circuits in typical atrial flutter, where conduction travels around the tricuspid annulus and isthmus-dependent pathways interact with right atrial anatomy. Electrophysiology mapping and ablation planning depend on recognizing where trabeculated myocardium transitions to smoother atrial wall, since catheter stability, local electrogram fractionation, and lesion formation often differ between these surfaces. Surgeons also use the right atrial appendage and adjacent pectinate field as a familiar landmark during venous cannulation and atriotomy, where avoiding unintended extension into thin-walled regions reduces bleeding risk. Use this illustration in cardiac anatomy teaching for medical and PA courses when explaining right atrial internal landmarks, or in cardiology and electrophysiology texts that discuss right atrial appendage anatomy in relation to atrial flutter circuits and catheter navigation. It also fits perioperative training materials for cardiothoracic and congenital heart surgery teams reviewing atrial entry sites and endocardial surface variation. Anatomical accuracy verified by SciePro's Medical Advisory Board.