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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. It terminates distally about 6 mm from the anal orifice. [citation needed]
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 urethral sphincter is a urethral sphincter muscle which constricts the internal urethral orifice. It is located at the junction of the urethra with the urinary bladder and is continuous with the detrusor muscle, [1][2] but anatomically and functionally fully independent from it. [3] It is composed of smooth muscle, so it is under ...
Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus. These are the internal anal sphincter and the external anal sphincter, which are circular muscles that normally maintain constriction of the orifice and which relax as required by normal physiological functioning. The ...
The external urethral sphincter is a striated muscle that allows voluntary control over urination. [4] 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. [5] The internal sphincter is present both in males ...
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. The microscopic precapillary sphincters function to control the blood flow into each capillary in response to local metabolic activity. [1]
The internal urethral orifice is the opening of the urinary bladder into the urethra. [1] Anatomy ... Internal sphincter muscle of urethra; References
The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. [1] It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional segment of the bowel, it functions to regulate release of excrement by two muscular sphincter complexes.