anal sphincter

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a circular muscle that constricts a passage or closes a natural orifice. When relaxed, a sphincter allows materials to pass through the opening. When contracted, it closes the opening. Four main sphincter muscles along the alimentary canal aid in digestion: the cardiac sphincter, the pyloric sphincter, and two anal sphincters. Other sphincters are found in the iris of the eye, the bile duct (sphincter of Oddi), the urinary tract, and elsewhere.
anal sphincter (sphincter a´ni) either of two sphincters (the internal and external anal sphincters) that open and close to control evacuation of feces from the anus.
cardiac sphincter a sphincter between the esophagus and the stomach, opening at the approach of food that can then be swept into the stomach by rhythmic peristaltic waves.
sphincter of Oddi a sheath of muscle fibers investing the associated bile and pancreatic passages as they traverse the wall of the duodenum.
pyloric sphincter a sphincter at the opening from the stomach into the duodenum; it is usually closed, opening only for a moment when a peristaltic wave passes over it.
urinary sphincter, artificial a fluid-filled system that surrounds the urethra with a silicone cuff that functions as a sphincter; a pump is in the scrotum and a fluid reservoir is in the abdomen. For urination, the pump's release valve is squeezed to allow the fluid to leave the urethral cuff and return to the reservoir; after urination is complete, the pump is squeezed and the fluid returns to the cuff to occlude the urethra.

ex·ter·nal a·nal sphinc·ter

a fusiform ring of striated muscular fibers surrounding the anus, attached posteriorly to the coccyx and anteriorly to the central tendon of the perineum; it is subdivided, often indistinctly, into a subcutaneous part, a superficial part, and a deep part for descriptive purposes.

anal sphincter

either of two sphincters (the internal and external anal sphincters) that open and close to control the evacuation of feces from the anus.

anal sphincter

A hybrid anatomic structure designed to control the anal opening, which is composed of an internal sphincter and an external spincter. Anal sphincter defects can be induced by forceps delivery.

anal sphincter

The double muscular ring surrounding the anal canal which, in conjunction with the thick, well-vascularized lining of the canal, produces a watertight seal except during defaecation.


relating to the anus.

anal abscess
acute, purulent infections in the area of the anus, usually caused by gram-negative organisms. In dogs, these most often arise from the anal sacs.
anal atresia, atresia ani
congenital absence or stenosis of the anus manifested by an absence of feces and a gradual development of abdominal distention. Fistulae may develop between the rectum and urogenital tract. The anomalous development can occur in several forms and may be accompanied by similar atresia at higher levels of the intestine. There is usually normal development of sphincters. A dimple is usually evident at the point at which surgical intervention is required.
anal canal
the short, terminal, retroperitoneal segment of the intestinal tract between the rectum and anus.
anal constriction
a congenital constriction combined with vulvar constriction occurs in Jersey cattle.
anal fibroma
occurs in cattle and excision effected for esthetic reasons.
anal fistula
see perianal fistula.
anal fold
see anal fold.
anal furunculosis
see perianal fistula.
anal membrane
the dorsal part of the cloacal membrane in the embryo; when it eventually breaks down the dorsal passage becomes the rectoanal passage.
anal-perineal laceration
see rectovaginal fistula.
anal prolapse
the protrusion of a small amount of mucosa through the anus.
anal reflex
the pursing of the anal orifice when the perineum is stimulated; indicative of an animal with intact sacral segments of the spinal cord.
anal sac
see anal sacs.
Enlarge picture
Anal sacs in the dog. By permission from McCurnin D, Poffenbarger EM, Small Animal Physical Diagnosis and Clinical Procedures, Saunders, 1991
anal sacculitis
inflammation of the anal sacs.
anal sphincter
the internal anal sphincter is formed from smooth muscle of the anal canal while the external anal sphincter, which is larger and of greater importance in fecal continence, consists of striated muscle.
anal sphincter hypertrophy
occurs in aged dogs and may give rise to difficult and painful defecation.
anal stenosis
scar formation after perianal fistulae, trauma, severe anal sac disease, or treatment for neoplasia may result in a reduced lumen and particularly a loss of the capacity to dilate with passage of feces. Straining, passage of ribbon-like feces and constipation result.
anal ulceration
inflammation and ulceration of the perianal skin which may be associated with anal sac disease. Seen most commonly in German shepherd dogs.
References in periodicals archive ?
Some authorities consider an early referral to physical therapy for pelvic floor exercises helpful in the immediate post-partum for all patients with obstetric anal sphincter injury (SOR: C).
The network warned that the result of this type of coding error could be a substantial underassessment of delivery-associated anal sphincter laceration as a maternal morbidity.
This study has shown that an injection of PermacolTM in patients with passive FI caused by a defect in the internal anal sphincter significantly improved the continence and quality of life.
Primary repair of obstetric anal sphincter rupture using the overlap technique.
obstetric anal sphincter injuries after episiotomy: systematic review and meta-analysis.
Conclusion: Anal sphincter injuries formed after vaginal delivery may be one of the reasons that increase the incidence of postmenopausal fecal incontinence and cause the formation of fecal incontinence symptoms in women.
When an anatomic defect is present in the anal sphincter and conservative treatment has not been successful, surgical correction is preferred.
Anal sphincter tone also is altered by nerve damage resulting from neurologic diseases, such as multiple sclerosis, Parkinson's disease, spinal cord injury, stroke, and diabetic neuropathy (Hayden & Weiss, 2011; Paris, Gourcerol, & Leroi, 2011).
Total anal sphincter saving technique for fistulain-ano: the ligation of intersphinteric fistula tract.
Obstetric anal sphincter injuries (OASIS) after vaginal delivery can affect a woman's physical and mental health, as well as future pregnancies.
Digital rectal palpation was highly painful as the external anal sphincter was inflamed and fibrosed.
It also identified presence or absence of disruption of external anal sphincter which is pivotal in differentiating between an inter and trans sphincteric fistula.