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The sphincter urethrae, or urethral sphincter, controlling the exit of urine from the body. At the anus, there are two anal sphincters which control the exit of feces from the body, the internal anal sphincter and external anal sphincter. The inner sphincter is involuntary and the outer is voluntary.
In males, the internal urethral sphincter has the additional function of preventing the flow of semen into the male bladder during ejaculation. [3] Females do have a more elaborate external sphincter muscle than males as it is made up of three parts: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae.
The internal anal sphincter, IAS, or sphincter ani internus is a ring of smooth muscle that surrounds about 2.5–4.0 cm of the anal canal. It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular muscle fibers of the rectum.
Generally, fissures are due to injury to the mucosa, or because of a poor local blood supply that prevents proper healing, with spasm of the external anal sphincter contributing. [9] The external anal sphincter can be relaxed by the application of glyceryl trinitrate creams, and constipation is managed with laxatives and improving hydration. [9]
The external anal sphincter (or sphincter ani externus) is an oval tube of skeletal muscle fibers. [1] Distally, it is adherent to the skin surrounding the margin of the anus . [ 2 ] It exhibits a resting state of tonical contraction [ 1 ] and also contracts during the bulbospongiosus reflex .
“Pelvic musculature needs to completely relax, which involves the pelvic floor lowering into the toilet bowl and the internal anal sphincter opening up,” so stool comes out uninhibited, he says.
The external urethral sphincter is a striated muscle that allows voluntary control over urination. [5] The internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the sympathetic division of the autonomic nervous system. [6] The internal sphincter is present both in males ...
Only then, once you’re aware, does your internal sphincter relax, and then you consciously relax your external sphincter. “Poop does not just come out without warning,” he says. “The ...