1. Formation of the Primitive Heart Tube: Around day 22 of gestation, two endocardial tubes fuse to form a single primitive heart tube. 2. Looping: This tube undergoes rightward looping to form the basic shape of the heart. 3. Septation: The heart tube partitions into four chambers: two atria and two ventricles. 4. Valve Formation: Development of the heart valves ensures unidirectional blood flow.