Rule 1: "Primitive" = Rough (Trabeculated) Think of "primitive" as an unpolished, rough stone. Primitive Atrium \bm{\rightarrow} Rough/Spongy part of the Atria Primitive Ventricle \bm{\rightarrow} Rough/Spongy part of the Ventricles Bulbus Cordis \bm{\rightarrow} Smooth outflow tract of ventricles 💡 Think: A light bulb is round and smooth. It forms the smooth exit tube. Rule 2: The Horns (Right goes Right, Left goes Coronary) The "Sinus Venosus" has two horns (Left and Right): Right Horn \bm{\rightarrow} Smooth Right Atrium 💡 Easy: Right Horn stays on the Right side! Left Horn \bm{\rightarrow} Coronary Sinus 💡 Think: Left = Coronary (the vein on the back of the heart). Rule 3: Top Veins vs. Bottom Veins (SVC vs. IVC) SVC (Superior = Top): Made by Cardinal veins (Right common/anterior). 💡 Think: High-ranking church Cardinals sit at the top (Superior). IVC (Inferior = Bottom): Made by Subcardinal and Posterior veins. 💡 Think: Sub means under/below (Inferior). Rule 4: The Center & The Pipes Truncus Arteriosus \bm{\rightarrow} Pulmonary Trunk & Ascending Aorta 💡 Think: Truncus forms the Trunk. Endocardial Cushion \bm{\rightarrow} Valves & Center Walls (Septa) 💡 Think: A cushion sits in the middle of the sofa. It forms the center wall and valves that cushion the doors of the heart. ⚡ Quick Cheat Sheet Make simple penmonic