The transverse perinei are paired muscles running from the ischial tuberosities to the central perineal body (perineal body), which is the fibromuscular node where multiple perineal structures converge and attach. The superficial transverse perineus is the thin surface layer; the deep transverse perineus (deep transverse perinei) is more substantial and contributes to the urogenital diaphragm. Obstetric perineal tears through the perineal body disrupt multiple muscles simultaneously.
| Origin | Inner surface of the ischial tuberosity and ischial ramus |
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| Insertion | Central perineal tendon (perineal body) |
| Nerve Supply | Perineal branch of the pudendal nerve (S2, S3, S4) |
| Blood Supply | Perineal artery |
| Actions | Fixes the perineal body as the central tendon of the perineum; Stabilises the perineal body during increases in intra-abdominal pressure; The deep transverse perineus also compresses the urethra (in females) and bulbourethral glands (in males) |
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The perineal body is the central structural hub of the perineum, and the transverse perinei muscles are its primary lateral supports. By pulling the perineal body toward the ischial tuberosities on each side, they maintain the structural integrity of the perineum and resist the downward forces of intra-abdominal pressure.
Obstetric third and fourth degree perineal tears disrupt the transverse perinei, bulbospongiosus, and external anal sphincter at the perineal body. Anatomical repair of each layer including the transverse perinei at primary repair reduces faecal incontinence rates. The perineal body can be assessed by bimanual examination between the posterior vaginal wall and anterior rectal wall.
The perineal body is palpable by pinching the tissue between the vaginal opening and the anus — its fullness and muscular tone indicate perineal body integrity.
Obstetric or traumatic perineal body damage disrupting the transverse perinei and adjacent structures producing perineal descent, faecal and urinary incontinence, and vaginal wall prolapse.
