Note the numerous epicardial ganglia that distribute on the root of superior vena cava, including the area of the sinoatrial node (SAN). The dotted line indicates the reflection of serious pericardium into epicardium that limits the venous part of heart hilum. The relationship of the distinctive fat pads (FP) (superior vena cava–aortic, right pulmonary veins, and inferior vena cava–left atrial ) with the epicardial ganglionated nerves stained histochemically for acetylcholinesterase seen as dark brown lines in the epicardium. Macrophotographs of Pressure-Inflated Canine Hearts Although surgical removal of the epicardial ganglia located at the junction of the inferior vena cava and inferior wall of the left atrium selectively eliminated the negative dromotropic effects of vagal nerve stimulation, surgical removal of the epicardial ganglia located around the right pulmonary veins attenuated the negative chronotropic response to vagal nerve stimulation without adversely affecting vagal inhibition of atrioventricular conduction ( Figures 2C and 2D) ( 6, 7).ĭownload Figure Download PowerPoint Figure 2 On the basis of physiological experiments, investigators determined that most GPs are embedded around 3 epicardial fat pads ( Figures 2A and 2B). Selective Innervation of the Sinoatrial and the Atrioventricular Nodesįor many years, studies of the hearts of larger mammals (e.g., canine, primate, ovine studies) have mostly focused on determining the location of epicardial ganglia by using histological examination of heart sections, an approach that led to the suggestion of the ganglionated plexuses (GPs) concept consisting of grouping ganglia in different sites ( 6–8). OTrV = orifice of the tributary vein of the right inferior pulmonary vein RSPV = right inferior pulmonary vein TrV = roots of the tributary veins. (E) The boxed area in D, in which the paired adrenergic (green) and cholinergic (red) post-ganglionic axons are clearly visible. The immunohistochemically stained nerve fibers are positive for both the adrenergic (green) and cholinergic (red) neuronal markers. (D) Microphotograph of neural meshwork of nerve fibers between cardiac myocytes of the right inferior pulmonary vein. Note that some neuronal somata are biphenotypic (i.e., they are simultaneously positive for adrenergic and cholinergic neuronal marker). (C) The small boxed area in B is magnified to demonstrate the ganglionic cells stained immunohistochemically for tyrosine hydroxylase (green) and for acetyltransferase (red), which are reliable neuronal markers for adrenergic and cholinergic intrinsic cardiac neurons, respectively. (B) The white frame on A is enlarged to illustrate the ganglionated nerves from which the nerves proceeding toward the walls of right inferior pulmonary vein originate. Note the course of epicardial ganglionated nerves extending from the middle dorsal ganglionated nerve subplexuses (MDsGP) to the root of the right inferior pulmonary vein. The dotted line indicates the reflection of serous pericardium into epicardium (heart hilum limits). (A) Macrophotograph of the posteroinferior surface of left atrium (LA) with the right inferior pulmonary vein (RIPV) stained histochemically for acetylcholinesterase. Nerve Supply of the Human RIPV by the MDsGP Download Figure Download PowerPoint Figure 1
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