[Ultrastructures of smooth muscles of the choledochus at the choledocho-duodenal junction].
The inner circular muscle (ICM) of the cat duodenum at the choledocho-duodenal junction is thickened, surrounding the choledochus at its proximal portion within the duodenal wall. Such a thickened portion of ICM is considered to be a main part which serves as a sphincter of the choledochus. This portion of the ICM was referred to as 'sphincter of choledochus' in the present study. The sphincter of choledochus and the adjacent ICM were studied by freeze-fracture and conventional thin sectioning methods by electron microscopy in order to clarify the morphological characteristics of smooth muscle cells in the sphincter of choledochus in comparison with ICM. Smooth muscle cells of the sphincter of choledochus were smaller (3-5 microns in diameter) in size, and had less developed dense patches and dense bands. However, they were richly innervated and had numerous gap junctions for electric coupling between cells. These findings indicate that sphincter of choledochus, though its contraction ability may be weaker than the ICM, can exhibit a highly synchronized contraction needed for the sphincter function.
Wakahara
T
T
Department of Surgery I, School of Medicine, Iwate Medical University, Morioka, Japan.
D000818:Animals; D002415:Cats; D003135:Common Bile Duct / Q000648:ultrastructure*; D004386:Duodenum / Q000648:ultrastructure; D005260:Female; D008297:Male; D008855:Microscopy, Electron, Scanning; D009130:Muscle, Smooth / Q000648:ultrastructure