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The atrioventricular valves of the guinea‐pig. I. A light microscopic study

1973; Wiley; Volume: 138; Issue: 3 Linguagem: Inglês

10.1002/aja.1001380304

1553-0795

Jeffrey P. Ellison, Richard G. Hibbs,

Cardiovascular Function and Risk Factors

Abstract The atrioventricular valves contain dense plexuses of adrenergic nerve fibers, derived from atrial and ventricular sources. Most of the adrenergic terminals are located in the lower third of the cusps. This region, which contains adrenergic terminals and acetylcholinesterase‐positive nerve endings is devoid of muscle fibers and blood vessels. The acetylcholinesterase‐positive endings may be sensory; and norepinephrine released from the adrenergic terminals may influence their performance. In the mitral valve, the atrial adrenergic plexus is separated from the ventricular plexus by a narrow zone that is free of adrenergic nerves. In most other respects the innervation, musculature and vascular supply of the mitral valve is similar to that of the tricuspid valve. Each valve has an intrinsic skeleton. This is made up of collagenous “ribs” that pass up from the chordae tendineae and fan out in the cusps. “Ribs” from adjacent chordae overlap and interweave, forming a complex support system. The musculature of the valves is complex and seems to have several functions. The annular muscle around the valve orifice may act as an atrioventricular sphincter, while offshoots that insert into the collagenous “ribs” of the cusp may assist the papillary muscles in maintaining tension on the cusps. The meshwork of muscle fibers between “ribs” may prevent ballooning of the cusps during systole. We found no consistent association between valvar muscles and nerves. Blood vessels are restricted mainly to the upper muscular part of the cusps, although a few capillary loops descend into the midzone of the cusps.