Rectal and Anal Muscles

The rectal muscles, from mucosa to serosa are the muscu-laris mucosae, an inner circular layer followed by an outer longitudinal layer (Figure 4-3.2). The inner muscular layer forms the rectal valves and transitions into the internal anal sphincter (IAS). The outer longitudinal layer extends from the sigmoid colon where it envelops the circumference but is thickest at the taenia coli. This muscle splays and becomes confluent at the rectosigmoid junction descending down the rectum to the anorectal junction. Fibers from this muscle descend into the intersphincteric groove where they splay out and may cross both the IAS and external anal sphincter (EAS) and ultimately insert on the perineal and perianal skin. Some of the fibers above the anorectal junction insert into the perineal body and the coccyx.

Figure 4-3.2. Muscular anatomy of the anus. (Reprinted from Fundamentals of Anorectal Surgery, 2nd ed,DE Beck,SD Wexner,page 7,© 1996, with permission from Elsevier)

the anal canal. The upper third of the rectum is peri-tonealized anteriorly and laterally, the middle third only anteriorly, and the lower third is retroperitoneal. The distal third of the rectum is related anteriorly to the vagina and uterus (prostate and seminal vesicles in men) and forms the rectouterine (or rectovesical) pouch or pouch of Douglas. The anterior peritoneal reflection lies approximately 5 to 8 cm from the perineal skin. The rectum has three folds, two on the left at 7 to 8 cm and 12 and 13 cm, and one on the right at 9 to 11 cm. The middle valve in the rectum corresponds to the level of the anterior peritoneal reflection. There are also three lateral curves. The upper and lower curves are convex to the left, and the middle is convex to the right. The rectum sits in a hollow anterior to the sacrum passing downward and posteriorly and then down and anteriorly to become the anal canal at the level of the pelvic floor. The anorectal ring (palpated as the puborectalis) is at the junction of the IAS and the levators.

Figure 4-3.2. Muscular anatomy of the anus. (Reprinted from Fundamentals of Anorectal Surgery, 2nd ed,DE Beck,SD Wexner,page 7,© 1996, with permission from Elsevier)

The EAS is a cylindrical-shaped voluntary skeletal muscle that lies outside the IAS. Proximally it abuts the puborectalis at the anorectal ring and extends distally beyond the level of the ZAS. The muscle is attached posteriorly to the anococcygeal ligament and the perineal body anteriorly.

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

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