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Perineal nerve
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The perineal nerve is a large terminal branch of the pudendal nerve. It usually originates from the pudendal nerve during its course through the pudendal canal or right after the nerve exits the canal. The pudendal nerve runs towards the perineum and terminates by bifurcating into two terminal branches: the superficial perineal nerve (superficial perineal branch) and the deep perineal nerve (deep perineal branch).
It is a common confusion between the terms 'peroneal' and 'perineal'; note that the term 'peroneal' refers to the structures located in the outer side of the calf, while 'perineal' describes the structures located in the area below the pelvic diaphragm.
The perineal nerve is a mixed nerve. Its sensory fibers are delivered via its superficial (sensory branch) while its motor fibers travel via its deep (motor) branch. The main function of this nerve is to provide sensory and motor supply for the structures of the urogenital triangle in both sexes.
This article will discuss the anatomy and function of the perineal nerve.
| Origin | Pudendal nerve |
| Branches | Superficial perineal nerve, deep perineal nerve |
| Sensory supply |
In males: Skin over the perineum, posterior scrotal skin In females: Labia minora, vaginal vestibule, inferior portion of vaginal canal, posterior aspect of the labia majora |
| Motor supply | Muscles of urogenital triangle (bulbospongiosus, ischiocavernosus and superficial transverse perineal muscle), external urethral sphincter, external anal sphincter, levator ani muscle |
Origin and course
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The perineal nerve is the terminal branch of the pudendal nerve. It typically originates in the last portion of the pudendal canal (within the Alcock's canal) or just as the pudendal nerve exits the canal. It runs anteriorly through the perineum, accompanied by the perineal artery. Soon after exiting the pudendal canal, the perineal nerve terminates in a bifurcation.
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Branches and innervation
The perineal nerve gives off two terminal branches. These branches include:
- The superficial perineal nerve
- The deep perineal nerve
Superficial perineal nerve
The superficial branch provides a sensory supply to the majority of the skin that covers the urogenital triangle. Additionally, it innervates the posterior scrotal area in males, and the labia minora, vaginal vestibule, and the posterior aspect of the labia majora and in females.
Deep perineal nerve
The deep perineal nerve is also known as the muscular or motor branch of the perineal nerve. This branch supplies the muscles of the urogenital triangle (bulbospongiosus, ischiocavernosus and superficial transverse perineal muscle), the external urethral sphincter and the anterior parts of the external anal sphincter and levator ani. This way the deep perineal nerve facilitates the act of micturition and sexual function (i.e. erection and ejaculation).
Additionally, this branch carries somatic sensations from all structures in the male and female superficial perineal space, i.e. erectile, muscular or glandular tissues, as well as the lower fifth of the vaginal canal.
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Clinical relations
Perineal nerve injury
In general, injuries of the perineal nerve are not very common. However, when they occur they can have serious consequences. This nerve is most often injured during car or motorcycle accidents, falls on the perineal area, sexual abuse, or other violent traumas. The most common symptoms of perineal nerve injuries are problems with bladder control or sexual problems.
Perineal nerve: want to learn more about it?
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