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Diagram of ileocaecal valve and sphincter. The sphincter pupillae, or pupillary sphincter, belonging to the iris in the eye. The orbicularis oculi muscle, a muscle around the eye. The upper oesophageal sphincters; The lower esophageal sphincter, or cardiac sphincter, at the upper portion of the stomach.
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 is the specialised thickened terminal portion of the inner circular layer of smooth muscle of the large intestine. It extends from the pectinate line (anorectal junction) proximally to just proximal to the anal orifice distally (the distal termination is palpable). Its muscle fibres are arranged in a spiral (rather ...
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 ]
A thickening of the muscularis mucosa, [citation needed] which is the smooth muscle tissue found beneath the mucosal layer of the digestive tract. A thickening of the muscularis externa is also noted. [1] There is also a variable amount of lymphatic tissue found at the valve. [3] The ileocecal valve has a papillose structure.
The muscle helps maintain continence of urine along with the internal urethral sphincter which is under control of the autonomic nervous system.The external sphincter muscle prevents urine leakage as the muscle is tonically contracted via somatic fibers that originate in Onuf's nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle.
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. [3] [4] [5] [6]
The pyloric sphincter, surrounding the pyloric orifice is a strong ring of smooth muscle at the end of the pyloric canal which lets food pass from the stomach to the duodenum. It acts as a valve , controlling the outflow of gastric contents into the duodenum [ 6 ] and release of chyme .