Category - Anal
The external anal sphincter (or sphincter ani externus ) is a flat plane of skeletal muscle fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus. Its action is entirely involuntary, and it is in a state of continuous maximal contraction. It helps the sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces. Sympathetic fibers from the superior rectal and hypogastric plexuses stimulate and maintain internal anal sphincter contraction. Its contraction is inhibited by parasympatheticfiber stimulation. The external anal sphincter receives somatic innervation from the inferior anal nerve, a branch of the pudendal nerve (s2-s4). Theres a quick and fun way to remember the innervation of the external anal sphincter! Just use the phrase s2, 3, 4 keep the poo off the floor. Fitzgerald, in pediatric gastrointestinal and liver disease (fourth edition), 2011. The anal sphincter consists of an inner ring of smooth muscle, the internal anal sphincter, the intersphincteric space, and an outer ring of skeletal muscle, the external anal sphincter. The internal sphincter is an involuntary muscle that maintains anal tone. other articles where external anal sphincter is discussed anal canal the external sphincter is a layer of voluntary (striated) muscle encircling the outside wall of the anal canal and anal opening. One can cause it to expand and contract at will, except during the early years of life when it is not yet fully developed. Internal anal sphincter surrounds the upper 23 of the anal canal. It is formed from a thickening of the involuntary circular smooth muscle in the bowel wall. External anal sphincter voluntary muscle that surrounds the lower 23 of the anal canal (and so overlaps with the internal sphincter). anal sphincter electromyography may be clinically useful in the evaluation of patients with urinary, bowel, and sexual dysfunction. It should be considered for all patients with a history and clinical examination suggestive of a central or peripheral sacral neuropathic lesion. The integration and coordination of the musculature of the pelvic floor and the anal sphincters is critical to two important physiological functions defecation and continence. Consequently, disorders affecting the pelvic floor muscles, the anal sphincters, their innervation or their precise coordination will, depending on their nature, result either in obstructed defecation or fecal incontinence. The internal and sphincter receives its parasympathetic nerve supply from the sacral outflow and its sympathetic supply from the thoracicolumbar outflow of the spinal cord. In order to investigate the influence of the tonic discharge of these nerves, eight healthy subjects receiving high spinal anaesthesia (t 6-t 12) and five receiving low spinal anaesthesia (l 5-s 1) were examined.