Primordial heart Primordial tube in transverse Heart loops Posterior view pericardial sac pericardial sinus (T) ventrally of adult heart Primordial arterial and venous Transverse ends are brought together to Pulmonary Aorta SVC pericardial sinus form transverse pericardial Arterial Venous trunk sinus. end end 6 Visceral Pulmonary Veins expand and pericardial pericardium veins IVC reflection is carried out around them to form oblique Parietal Pericardial pericardial sinus. pericardium cavity Area of oblique Lateral views of embryonic heart pericardial sinus Fig1.25 Development of heart and pericardium Fig1.25 Development of heart and pericardium