Structure and Innervation of the Extrahepatic Biliary System in the Australian Possum, Trichosurus Vulpecula

Abstract

The morphology, microanatomy and innervation of the biliary tree of the Australian possum, Trichosurus vulpecula, was examined. The gross morphology of the gallbladder, hepatic and cystic ducts, and the course of the common bile duct, conforms to those of other species. The sphincter of Oddi has an extraduodenal segment that extends 15mm from the duodenal wall; within this segment the pancreatic and common bile ducts are ensheathed together by sphincter muscle. Their lumens unite to form a common channel within the terminal intraduodenal segment. Nerve cell bodies of the gallbladder were found in an inter-connecting network of ganglia that were located in the serosa, muscularis and mucosa. Nerve fibres innervated the muscle, arterioles and the mucosa. Few ganglia were found along the supra sphincteric portion of the common bile duct. Nerve trunks followed the duct and a dense nerve fibre plexus was found in the mucosa. In the sphincter most ganglia were located in two plexuses, the first between the layers of the external sphincter muscle, which was continuous with the external muscle of the duodenum, and the second was associated with the internal sphincter muscle. Nerve fibres were numerous in the sphincter muscle, and were also found in the subepithelial and periglandular plexuses of both the pancreatic and common bile ducts.

Characterization of the intrinsic and extrinsic innervation of the gall bladder epithelium in the Australian Brush‐tailed possum (Trichosurus vulpecula)

“…In this respect, the innervation of the gall bladder appears to be similar to the innervation of the stomach, where sensory mediation is proposed to be primarily via the action of extrinsic afferent nerves 39,40 . We demonstrate an extensive innervation of the gall bladder by nerves which colocalized SP and CGRP, identified previously as spinal afferent nerves, in this species 33 . The presence of a spinal afferent innervation of the gall bladder has been demonstrated previously in several species including human beings 26,33,41,42 .…”

Distribution of nitric oxide synthase and vasoactive intestinal polypeptide immunoreactivity in the sphincter of Oddi and duodenum of the possum

“…1). These run side by side, surrounded by sphincteric muscle (Padbury et al 1993b). The distal end of the SO consists of the papilla of Vater, located within the duodenal wall and represents the common opening of the CBD and PD into the duodenum.…”

“…The neural plexuses within the SO have been demonstrated to bear a close similarity to those of the intestine (Cai and Gabella 1983;Wells and Mawe 1993). In addition to the myenteric ganglia, a rich ganglionated submucosal plexus has been demonstrated together with a dense innervation of the muscle layers in the possum (Padbury et al 1993b) and in the pig and human SO (Sand et al 1997). The present study also shows a similar overall organisation of nerve plexuses in the possum SO and duodenum to those described elsewhere in the gastrointestinal tract (Furness and Costa 1987;Clerc et al 1998).…”

The distribution and chemical coding of neurons supplying the sphincter of Oddi in mammals

“…Ganglionated plexuses distributed between the muscles of the SO have been described in detail by Padbury et al (1993a) in the Australian brush tailed possum. The authors used anti-neuron specific enolase (NSE) and anti-S100 immunohistochemistry to visualize neurons and anti-desmin antibodies for muscle identification.…”