While a digital arteriovenous anastomosis (Hoyer-Grosser's organ, Masson's glomus) is a well-known structure, photographic evidence of communication between arterial and venous lumens might not be demonstrated in routine histological or immunohistochemical analysis. Abundant clusters of so-called glomera were found in semi-serial sections of the distal aspect of 14 fingers obtained from 7 donated elderly cadavers. Two to six round or oval clusters were observed in each longitudinal section (over 0.3-0.6 mm in maximum diameter) in subcutaneous tissue 0.5-1.5 mm below the basal layer of the skin, whereas none were often observed in transverse sections. Lumen-to-lumen communication between arteriole and venule at 8 sites in 2 cadavers was identified in these clusters of glomera. The opening in the arteriole was large (50 μm in diameter) at 3 sites in specimens from an 80-year-old man, whereas it was small (10-30 μm) at 5 sites in those from a 91-year-old man. The arterial aspect was tightly surrounded by abundant nerve fibers expressing tyrosine hydroxylase immunoreactivity, whereas the venous part was not. No or little expression of S100 protein immunoreactivity suggested that these nerve fibers were unmyelinated. The morphology at the lumen-to-lumen communication was simple - possibly an end-to-end anastomosis - rather than a sinuous curve of arteriole opening on to a short funnel-shaped venule as seen in the standard textbooks.
Keywords: Digital arteriovenous anastomosis; Hoyer-Grosser’s organ; Immunohistochemistry; Masson’s glomera; Vascular lumen.