[The longitudinal muscle of the anal canal]

The longitudinal muscle (LM) represents a strong muscular structure of the anal canal situated between the internal (IAS) and the external anal sphincter (EAS). Terminal fibres of this muscle insert at the submucosa of the anal canal, representing the m. canalis ani. Others cross the subcutaneous part of the EAS to become the m. corrugator ani. Thus, the LM connects the visceral and somatic parts of the anal sphincter complex. Histologically ganglionic cells and as Vater-Pacinian corpuscles can be identified inside the LM. Morphology, topography and histology of the LM suggest that this muscle participates in maintaining anorectal continence. It is mandatory that the exact functions of this muscular structure be to elaborated upon, if we are to understand the mechanism of anorectal continence.