GROSS AND MICROSCOPIC ANATOMY OF THE HUMAN INTRINSIC CARDIAC NERVOUS-SYSTEM

Background: The extent and locations of intrinsic cardiac ganglia on t he human heart were investigated to facilitate studying their function . Methods: The locations and number of major intrinsic cardiac ganglia were determined in six human hearts by means of microdissection follo wing methylene blue staining. Light and electron microscopic analyses were performed on right atrial and cranial medial ventricular ganglia obtained from 12 other human hearts. Results: Gross anatomy: Collectio ns of ganglia associated with nerves, i.e., ganglionated plexuses, wer e observed consistently in five atrial and five ventricular regions. O ccasional ganglia were located in other atrial and ventricular regions . Atrial ganglionated plexuses were identified on 1) the superior surf ace of the right atrium, 2) the superior surface of the left atrium, 3 ) the posterior surface of the right atrium, 4) the posterior medial s urface of the left atrium (the latter two fuse medially where they ext end anteriorly into the interatrial septum), and 5) the inferior and l ateral aspect of the posterior left atrium. Ventricular ganglionated p lexuses were located in fat 1) surrounding the aortic root, 2) at the origins of the right and left coronary arteries (the latter extending to the origins of the left anterior descending and circumflex coronary arteries), 3) at the origin of the posterior descending coronary arte ry, 4) adjacent to the origin of the right acute marginal coronary art ery, and 5) at the origin of the left obtuse marginal coronary artery. Microscopic anatomy: Ganglia ranged in size from those containing a f ew neurons to large ganglia measuring up to 0.5 x 1 mm. The human hear t is estimated to contain more than 14,000 neurons. Neuronal somata va ried in size and shape. Many axon terminals in intrinsic cardiac gangl ia contained large numbers of small, clear, round vesicles that formed asymmetrical axodendritic synapses, whereas a few axons contained lar ge, dense-cored vesicles. Conclusions: The human intrinsic cardiac ner vous system is distributed more extensively than was considered previo usly, most of its ganglia being located on the posterior surfaces of t he atria and superior aspect of the ventricles. Each ganglion therein contains a variety of neurons that are associated with complex synapto logy. (C) 1997 Wiley-Liss, Inc.