Where is the deep perineal nerve located? Understanding its pelvic floor anatomy

The perineal nerve, a branch of the pudendal nerve, is typically found within the pudendal canal before it divides into two terminal branches: the superficial and deep perineal nerves. The deep perineal nerve then proceeds to innervate the muscles of the pelvic floor, particularly in the urogenital triangle.

Quick Summary

The deep perineal nerve is a motor and sensory branch of the pudendal nerve, located in the deep perineal pouch of the pelvic floor, where it supplies key muscles of the urogenital triangle.

Key Points

• Origin: The deep perineal nerve is a terminal branch of the perineal nerve, which is a branch of the pudendal nerve.

• Location: It resides in the deep perineal pouch, located within the urogenital triangle of the pelvic floor.

• Motor Function: Its primary role is motor innervation, controlling key muscles in both the superficial and deep perineal pouches.

• Muscle Innervation: It supplies the external urethral sphincter, deep transverse perineal, ischiocavernosus, and bulbospongiosus muscles.

• Clinical Importance: Injury or compression can lead to incontinence, pelvic floor dysfunction, and sexual issues due to its control over the sphincter and other perineal muscles.

• Distinction from Peroneal Nerve: It is distinct from the deep peroneal (fibular) nerve, which is located in the lower leg and foot.

The human body contains a complex network of nerves, and understanding the location of specific ones like the deep perineal nerve is crucial for grasping how the body's systems, especially the pelvic region, function. This nerve is a vital component of the pudendal nerve system, responsible for motor control and sensation in the perineum.

The Anatomical Placement of the Deep Perineal Nerve

The deep perineal nerve's location is best understood by tracing its origin and course through the pelvic region. As one of two terminal branches of the perineal nerve, its journey begins deep within the pelvis before moving into the perineal area.

Origin and Course from the Pudendal Nerve

• Parent Nerve: The deep perineal nerve is a branch of the perineal nerve, which is, in turn, the larger of the two terminal branches of the pudendal nerve.
• Pudendal Canal: The pudendal nerve and its branches run through a space called the pudendal (or Alcock's) canal, a fibrous sheath formed by the obturator fascia on the medial wall of the ischioanal fossa. The perineal nerve typically branches off the pudendal nerve either within the canal or shortly after it exits.
• Bifurcation: The perineal nerve bifurcates into the deep (muscular) perineal nerve and the superficial (cutaneous) perineal nerve. The deep branch travels anteriorly into the urogenital triangle, alongside the perineal artery.

Location within the Perineum

The perineum is a diamond-shaped region at the outlet of the pelvis, divided into the posterior anal triangle and the anterior urogenital triangle. The deep perineal nerve is located entirely within the urogenital triangle, specifically in the deep perineal pouch. This pouch is situated between the pelvic floor muscles superiorly and the perineal membrane inferiorly.

Functions and Innervation

The deep perineal nerve is primarily a motor nerve with some sensory fibers.

• Motor Innervation: It provides motor supply to muscles in the superficial and deep perineal pouches. These include the external urethral sphincter for urinary control, the deep transverse perineal muscle for pelvic floor support, and the ischiocavernosus and bulbospongiosus muscles which are involved in sexual function. It may also innervate the anterior part of the external anal sphincter.
• Sensory Innervation: It carries sensation from structures in the superficial perineal space, such as erectile tissues, muscles, glands, and the lower vaginal canal.

Deep Perineal vs. Deep Peroneal Nerves: A Crucial Distinction

It is important to distinguish between the deep perineal nerve and the deep peroneal (fibular) nerve, which have similar names but vastly different locations and functions. The deep perineal nerve is in the pelvic floor, branching from the pudendal nerve, and is primarily involved in pelvic floor muscle control and sensation in the perineum. In contrast, the deep peroneal nerve is located in the lower leg and foot, originating from the sciatic nerve via the common peroneal nerve. Its main function is motor control for ankle and toe movement and sensation in the foot. A table comparing these nerves is available in the referenced documents.

Clinical Relevance of the Deep Perineal Nerve

The deep perineal nerve's role in controlling pelvic floor and sphincter muscles makes it clinically significant for micturition and sexual function. Issues with the pudendal nerve, its parent nerve, can lead to various problems.

Potential Nerve Issues

• Pudendal Nerve Entrapment: Compression of the pudendal nerve in Alcock's canal can result in chronic pelvic pain (pudendal neuralgia), affecting the deep perineal nerve and its innervated structures.
• Trauma or Surgery: Injuries during childbirth or pelvic surgery can damage the deep perineal nerve, potentially causing urinary or fecal incontinence and sexual dysfunction.
• Pelvic Floor Dysfunction: Weakness or damage to the nerve contributes to pelvic floor disorders. Understanding and strengthening these muscles is important for pelvic health. For additional information on pelvic anatomy, the resource Physiopedia is a useful reference.

Conclusion

The deep perineal nerve is a vital component of the pelvic floor, situated in the deep perineal pouch of the urogenital triangle. Originating from the pudendal nerve, it is crucial for controlling muscles involved in urinary continence and sexual function. Recognizing its specific location and differentiating it from the deep peroneal nerve is key to understanding the complex anatomy and clinical importance of this region.

Frequently Asked Questions

What is the primary function of the deep perineal nerve?

The primary function is motor innervation of the pelvic floor muscles within the deep perineal pouch. It controls muscles like the external urethral sphincter and those involved in erection and ejaculation.

What happens if the deep perineal nerve is damaged?

Damage to the deep perineal nerve can result in urinary or fecal incontinence due to impaired sphincter control. It can also lead to sexual dysfunction and chronic pelvic pain.

Is the deep perineal nerve the same as the deep peroneal nerve?

No, they are different. The deep perineal nerve is in the pelvis, branching from the pudendal nerve, while the deep peroneal nerve is in the lower leg and foot, branching from the common peroneal nerve.

Which muscles does the deep perineal nerve innervate?

It innervates several muscles, including the external urethral sphincter, deep transverse perineal muscle, ischiocavernosus, and bulbospongiosus.

Where does the deep perineal nerve originate?

It originates from the perineal nerve, which is a branch of the pudendal nerve. The pudendal nerve itself comes from the S2-S4 sacral plexus.

Can pelvic floor physical therapy help with deep perineal nerve issues?

Yes, pelvic floor physical therapy is often used to address weakness or dysfunction in the muscles supplied by the deep perineal nerve, especially in cases of incontinence or pelvic pain.

What is the pudendal canal, and how does it relate to the deep perineal nerve?

The pudendal canal (Alcock's canal) is a fibrous sheath in the pelvis that the pudendal nerve and its branches, including the deep perineal nerve, pass through. It is a common site for nerve compression.