Functional Adaptability of the Tunica Media of the Atriopulmonary Junction

Introduction: The histoarchitecture of the tunica media of the Atriopulmonary Junction (APJ) has not been extensively studied and yet the tunica media is the backbone, which provides the structural strength for optimum function. This study therefore strives to unravel the structural components of the tunica media of the APJ. Methods: The study design was a descriptive cross-sectional study. Histological studies were done on tissues from the APJ of 20 hearts using light microscopy. The proportion of elastic fibers in the tunica media of the APJ was determined using the point intercept method by dropping a grid in ImageJ software. Results: The smooth muscle cells were concentric and more prominent in males extending the entire extent of the tunica media compared to females where they were confined to the intimal side of tunica media. The collagen bundles were mainly longitudinal. The elastic fibers showed a diverse pattern of organization and side and sex differences in orientation and quantity. Conclusion: Gender and regional variations in the histology of the tunica media of the pulmonary veins suggest a mechanism for controlling hemodynamic forces at the APJ.