Angioarchitecture of gallbladder in pig: LM and SEM study on vascular microcorrosion casts.

The study focused on the description of pig gallbladder angioarchitecture, with particular emphasis on the specifics of the course of blood vessels in individual layers of the gallbladder wall. Furthermore, the vascular systems of the pig gallbladder were analyzed in terms of the adaptation of this organ to changes in its volume during cyclical bile storage and discharge. The gallbladder is supplied by the cystic artery, which in the pig represents a mixed pinnate and bipinnate pattern of branching. The light microscopic and scanning electron microscopic observations of three-dimensional vascular corrosion casts showed the presence of two main complex vascular networks in the wall of the gallbladder, one located in the subserosal and the other in the mucosa. The unique features in the pig, connected with the size of the gallbladder, is the well-developed horizontal venous plexus under folds of the mucosa, which is a voluminous reservoir of fluids absorbed from bile and vascular networks around mucous glands. Superficial blood vessels of the gallbladder run in vascular pairs or triads, where a single artery runs between two veins. The structures of blood flow control, that is, venous valves, were observed only in venules of the subserosal plexus. Spatial arrangement of the vascular network in the pig gallbladder shows functional plasticity during changes in gallbladder volume. The course of superficial blood vessels in the well-filled gallbladder is arcuate, while in the empty gallbladder it is undulated or spiral. In the mucosal and intramural vessels the direction of blood vessels may change from perpendicular to oblique.