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Third-degree tear: fourchette, perineal skin, vaginal mucosa, muscles, and anal sphincter are torn; third-degree tears may be further subdivided into three subcategories: [6] 3a: partial tear of the external anal sphincter involving less than 50% thickness; 3b: greater than 50% tear of the external anal sphincter; 3c: internal sphincter is torn
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 two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut. The external urethral sphincter originates at the ischiopubic ramus and inserts into the intermeshing muscle fibers from the other side.
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 ...
muscles Deep transverse perineal muscles; External sphincter muscle of male urethra; External sphincter muscle of female urethra; Compressor urethrae muscle in the female is sometimes included [3] Urethrovaginal sphincter in the female is sometimes included [3] other Membranous urethra in the male; proximal portion of urethra in the female
The function of the muscle is fixation of the perineal body (central tendon of perineum), support of the pelvic floor, expulsion of semen in males and last drops of urine in both sexes. [2] The deep transverse perineal muscle lies in the same plane as the urethral sphincter and formerly the two muscles were described together as the constrictor ...
Perineal tears and episiotomy often occur in childbirth with first-time deliveries, but the risk of these injuries can be reduced by preparing the perineum, often through massage. [8] At this point, the following muscles converge and are attached: External anal sphincter; Bulbospongiosus muscle; Superficial transverse perineal muscle
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 ]