A concept of the anatomy of the anal sphincter mechanism and the physiology of defecation

Abstract

A review of the new concepts of the anatomy of the anal sphincter mechanism and the physiology of defecation is presented. The external sphincter is a triple-loop system; each loop can function as a separate sphincter through voluntary inhibition action and mechanical compression. Stress defecation resulting from internal sphincter damage is described. A new technique for repair of rectal incontinence is presented, which depends on inducing continence not only by mechanical compression, but also by voluntary inhibition. The mechanism of defecation and rectal continence is described and four types of incontinence presented. Also, the mechanism of both the levator dysfunction syndrome and prolapse is demonstrated and a technique of repair is presented. The study defines two types of rectal anomalies; suprahiatal and infrahiatal. The role of the embryonic anorectal sinus, anorectal band, and epithelial debris in the genesis of perirectal suppuration, chronic anal fissure, pruritus ani, and hemorrhoids is described. The communicating veins, identified between the hemorrhoidal and vesical plexuses, offer an explanation for the vague pathologic aspects of recurrent bacteriuria, urethral discharge, cervicitis, and vaginitis, and provide a proper line for their treatment. They also serve to perform a new radiographic technique--anal cystography--and to administer drugs, including chemotherapeutics, in the treatment of pelvic malignancies.

Bowel dysfunction following spinal cord injury

“…Just inside the anus is the external anal sphincter (EAS) complex, described by Sha®k as three counterpoised U-shaped loops (Figure 1). 10 The upper loop, formed mainly by puborectalis, arises from the symphisis pubis, loops around the upper part of the rectal neck and opens ventrally. It is innervated by the inferior haemorrhoidal nerve.…”

“…It is supplied by the inferior haemorrhoidal nerve. 10,11 As each loop has its own separate bilateral nerve supply, each can function as a sphincter independently.…”

Anourethral reflex. Description of a reflex and its clinical significance: preliminary study

“…They function to oppose, inter rupt or terminate the act of evacuation. 6,7 The levator ani muscle is a funnel with a transverse part called the levator plate and a vertical part called the suspensory slingS (Fig 1). It is a vesical and rectal neck dilator, whereas the puborectalis is a neck constric tor.…”

Simplified anal sphincter anatomy

“…Oh et al (1972) reported that the EAS comprised of two compartments, superficial and deep compartments, each of the compartments composed of two layers of sphincter muscles. Shafik (1975) popularized the triple-loop system of the EAS. Regarding the levator ani, it is generally accepted that this muscle is divided into three distinct muscles, the puborectalis, pubococcygeus, and iliococcygeus.…”