Inside the right atrium, a muscular ridge separates the smooth-walled posterior portion receiving the venae cavae from the trabeculated anterior portion. It marks the position of the SA node and corresponds externally to the sulcus terminalis. What is this ridge called?

• A Crista terminalis ✓
• B Limbus fossae ovalis
• C Tendon of Todaro
• D Pectinate line

Explanation

The crista terminalis is the C-shaped muscular ridge derived from the junction between the embryonic sinus venosus and primitive right atrium. It separates the smooth sinus venarum from the pectinate muscle region and carries the SA node at its upper end near the SVC opening. The limbus bounds the fossa ovalis on the interatrial septum, and the tendon of Todaro forms one boundary of the triangle of Koch.

Reference: Gray's Anatomy for Students, 4th ed.

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