Superficial perineal pouch

The superficial perineal pouch is a potential space in the perineum, located within the urogenital triangle, just below the perineal membrane. This pouch contains muscles, blood vessels, nerves, and erectile tissues that are involved in the function of the external genitalia. It plays an important role in sexual and urinary functions and is anatomically different in males and females due to the reproductive organs.

Location

The superficial perineal pouch is located in the urogenital triangle of the perineum, between the perineal membrane (superiorly) and the Colles’ fascia (inferiorly). The pouch lies just beneath the skin and superficial fascia of the perineum. In males, it contains structures related to the penis, while in females, it includes structures associated with the clitoris and vulva. The boundaries of the pouch are formed by the pubic symphysis anteriorly and the ischial tuberosities laterally, with the posterior limit blending with the perineal body.

Structure and Anatomy

The superficial perineal pouch is an important anatomical space in the urogenital triangle of the perineum. It houses various muscles, erectile tissues, glands, and neurovascular structures. The pouch plays a crucial role in supporting the external genitalia and facilitating sexual and urinary functions. Its contents differ slightly between males and females due to the anatomy of the reproductive organs, but the overall structure of the pouch is consistent.

Boundaries of the Superficial Perineal Pouch

• Inferior Boundary:The inferior boundary of the superficial perineal pouch is formed by the Colles’ fascia (superficial perineal fascia). This fascial layer encloses the contents of the pouch and provides structural support for the external genitalia.
• Superior Boundary:The superior boundary of the superficial perineal pouch is the perineal membrane. This fibrous layer separates the superficial perineal pouch from the deep perineal pouch and supports the muscles and tissues of the perineum.
• Lateral Boundaries:The lateral boundaries are formed by the ischial tuberosities and ischiopubic rami, bony structures that provide support and serve as attachment points for the muscles within the pouch.
• Anterior Boundary:The anterior boundary of the pouch is connected to the pubic symphysis, the joint that unites the two pubic bones of the pelvis.
• Posterior Boundary:The posterior boundary of the superficial perineal pouch blends into the perineal body, a fibromuscular structure located at the midpoint of the perineum between the anus and external genitalia. This structure serves as an important attachment point for several perineal muscles.

Contents of the Superficial Perineal Pouch in Males

In males, the superficial perineal pouch contains structures related to the external genitalia and reproductive system, including muscles, erectile tissue, and neurovascular structures.

Muscles:

• Bulbospongiosus Muscle: This paired muscle surrounds the bulb of the penis and helps expel urine and semen from the urethra. It also contributes to the erection by compressing the base of the penis and helping to empty the urethra of residual fluid.
• Ischiocavernosus Muscle: This muscle covers the crura (roots) of the penis and helps maintain penile erection by compressing the crura, preventing venous return, and directing blood into the erectile tissues of the penis.
• Superficial Transverse Perineal Muscle: This muscle runs transversely across the perineum, attaching to the perineal body. It provides structural support to the perineal body and helps stabilize the position of the perineum.

Erectile Tissues:

• Bulb of the Penis: The bulb is the expanded proximal part of the corpus spongiosum, one of the erectile tissues of the penis. It plays a role in the engorgement of the penis during erection.
• Crura of the Penis: The crura are the proximal parts of the corpora cavernosa, which attach to the ischial rami. These paired erectile tissues form the main body of the penis and are responsible for penile erection.

Neurovascular Structures:

• Dorsal Nerve of the Penis: This nerve provides sensory innervation to the penis and runs through the superficial perineal pouch to the external genitalia.
• Dorsal Arteries and Veins of the Penis: These vessels supply blood to and drain blood from the penis. They run through the pouch and contribute to the vascular supply necessary for erectile function.

Contents of the Superficial Perineal Pouch in Females

In females, the superficial perineal pouch contains structures related to the external genitalia, including muscles, erectile tissues, and glands.

Muscles:

• Bulbospongiosus Muscle: In females, this paired muscle surrounds the bulbs of the vestibule and functions to compress the vestibular glands, aiding in lubrication during sexual arousal. It also plays a role in narrowing the vaginal opening during sexual activity.
• Ischiocavernosus Muscle: Similar to males, this muscle covers the crura of the clitoris and helps maintain clitoral erection by compressing the crura and restricting venous return from the erectile tissues.
• Superficial Transverse Perineal Muscle: This muscle provides structural support to the perineal body and helps stabilize the perineal region during physical activity.

Erectile Tissues:

• Bulbs of the Vestibule: These are paired erectile structures that lie on either side of the vaginal opening. They are homologous to the bulb of the penis in males and become engorged during sexual arousal.
• Crura of the Clitoris: These are paired structures that form the body of the clitoris. They attach to the ischiopubic rami and contribute to clitoral erection during sexual arousal.

Glands:Greater Vestibular (Bartholin’s) Glands: These paired glands are located on either side of the vaginal opening, deep to the bulbospongiosus muscles. They secrete mucus that lubricates the vestibule of the vagina during sexual arousal.

Neurovascular Structures:

• Dorsal Nerve of the Clitoris: This nerve provides sensory innervation to the clitoris, running through the superficial perineal pouch to reach the external genitalia.
• Dorsal Arteries and Veins of the Clitoris: These vessels supply and drain blood from the clitoris, contributing to clitoral engorgement during sexual arousal.

Key Muscles in the Superficial Perineal Pouch

The muscles in the superficial perineal pouch are essential for supporting the external genitalia, facilitating sexual function, and contributing to the stability of the perineal region:

• Bulbospongiosus Muscle:This muscle, present in both males and females, compresses the erectile tissues during sexual arousal and assists in expelling fluids from the urethra (in males) and lubricating the vaginal vestibule (in females). Its rhythmic contractions play a role in orgasm.
• Ischiocavernosus Muscle:The ischiocavernosus muscle compresses the crura of the penis or clitoris, helping to maintain erection by restricting venous return from the erectile tissues. In both males and females, this muscle is crucial for the maintenance of sexual function.
• Superficial Transverse Perineal Muscle:This small, paired muscle helps stabilize the perineal body, providing support for the perineum and contributing to the function of the pelvic floor. It plays a role in maintaining the integrity of the pelvic floor, particularly during increases in intra-abdominal pressure.

Erectile Tissues in the Superficial Perineal Pouch

Erectile tissues in the superficial perineal pouch play an essential role in sexual function. These tissues become engorged with blood during sexual arousal, contributing to erection in males and females:

• Bulb of the Penis (Males) / Bulbs of the Vestibule (Females):The bulb of the penis (in males) and the bulbs of the vestibule (in females) are erectile tissues that engorge with blood during sexual arousal. In males, the bulb of the penis is part of the corpus spongiosum, while in females, the bulbs of the vestibule lie on either side of the vaginal opening.
• Crura of the Penis (Males) / Crura of the Clitoris (Females):The crura form the main erectile tissues of the penis in males and the clitoris in females. These structures attach to the ischiopubic rami and play a critical role in the erection of the external genitalia during sexual arousal.

Neurovascular Supply

The superficial perineal pouch contains essential neurovascular structures that innervate and provide blood flow to the external genitalia:

• Nerves:The dorsal nerve of the penis (in males) or dorsal nerve of the clitoris (in females) runs through the superficial perineal pouch, providing sensory innervation to the external genitalia. These nerves are branches of the pudendal nerve, which is the main nerve supplying the perineum.
• Blood Vessels:The dorsal arteries and veins of the penis or clitoris supply and drain blood from the erectile tissues. These vessels are vital for achieving and maintaining erection during sexual activity.

Function

The superficial perineal pouch plays a critical role in supporting the external genitalia, assisting in sexual function, and maintaining the structural integrity of the perineum. It contains muscles, erectile tissues, and neurovascular structures that contribute to sexual arousal, lubrication, and urinary continence. The functions of the superficial perineal pouch differ slightly between males and females due to anatomical differences, but its overall role in the urogenital system is similar in both genders.

Support of External Genitalia

The superficial perineal pouch provides structural support to the external genitalia in both males and females. The muscles and connective tissues in this pouch stabilize and anchor the erectile tissues and associated structures, ensuring proper positioning during sexual activity.

• In Males:The bulbospongiosus muscle surrounds the bulb of the penis and helps stabilize the penile shaft during erection. The ischiocavernosus muscle compresses the crura of the penis, maintaining the rigidity of the penis during sexual arousal.
• In Females:The bulbospongiosus muscle surrounds the bulbs of the vestibule, supporting the labia and vaginal opening. The ischiocavernosus muscle covers the crura of the clitoris, supporting the clitoral shaft during sexual arousal.

The structural support provided by these muscles ensures that the external genitalia remain positioned correctly during physical activities, including sexual intercourse, preventing displacement or injury.

Facilitation of Sexual Function

The superficial perineal pouch plays a crucial role in sexual function by supporting the erectile tissues and facilitating sexual arousal in both males and females.

• Erection in Males:The ischiocavernosus muscle compresses the crura of the penis, helping to trap blood within the corpora cavernosa (erectile tissues), maintaining penile erection. The bulbospongiosus muscle compresses the bulb of the penis, aiding in the engorgement of the corpus spongiosum, which supports the urethra and contributes to a firm erection.
• Erection in Females:The ischiocavernosus muscle compresses the crura of the clitoris, helping maintain clitoral engorgement by restricting venous return from the erectile tissues. The bulbospongiosus muscle compresses the bulbs of the vestibule, enhancing the engorgement of the vaginal opening during sexual arousal.

These muscles enhance blood flow to the erectile tissues, contributing to sexual pleasure, arousal, and orgasm in both males and females.

Assistance in Ejaculation and Semen Expulsion (Males)

In males, the bulbospongiosus muscle plays an important role in the expulsion of semen during ejaculation. The rhythmic contractions of the bulbospongiosus muscle compress the bulb of the penis and the corpus spongiosum, propelling semen through the urethra and out of the penile opening.

Compression of Urethra:The bulbospongiosus muscle compresses the urethra, aiding in the expulsion of semen and ensuring the complete emptying of the urethra after ejaculation.

This action is essential for the effective transfer of semen during ejaculation and contributes to the proper functioning of the male reproductive system.

Lubrication of the Vaginal Vestibule (Females)

In females, the superficial perineal pouch contains the greater vestibular (Bartholin’s) glands, which are responsible for secreting mucus to lubricate the vaginal vestibule during sexual arousal.

Secretion of Mucus:The Bartholin’s glands secrete mucus that helps to lubricate the vaginal opening, facilitating comfortable sexual intercourse. The secretion is triggered by sexual stimulation and is critical for reducing friction during penetration.

The bulbospongiosus muscle in females also assists in the expulsion of fluid from the Bartholin’s glands, contributing to vaginal lubrication during sexual arousal.

Urinary Continence

The muscles within the superficial perineal pouch, particularly the bulbospongiosus muscle in both males and females, contribute to the control of the external genitalia and urethra, aiding in the maintenance of urinary continence.

Control of Urethra:The bulbospongiosus muscle in males assists in the expulsion of the last drops of urine from the urethra after urination, ensuring complete emptying of the urinary tract. In females, this muscle helps to maintain the position of the external genitalia and may assist in controlling the urinary stream.

By assisting in the expulsion of urine and ensuring the proper functioning of the external genitalia, the muscles in the superficial perineal pouch contribute to the maintenance of urinary continence.

Stabilization of the Perineal Body

The superficial transverse perineal muscle helps stabilize the perineal body, which is a central structure in the perineum. The perineal body serves as a point of attachment for several muscles of the pelvic floor, including those in the superficial and deep perineal pouches.

• Support for Pelvic Floor:The superficial transverse perineal muscle provides structural support to the pelvic floor by stabilizing the perineal body. This helps maintain the integrity of the perineum during physical activities, such as walking, running, and childbirth.
• Prevention of Pelvic Organ Prolapse:By stabilizing the perineal body, the superficial transverse perineal muscle helps prevent the downward displacement or prolapse of pelvic organs, including the bladder, uterus, and rectum.

Coordination with Deep Perineal Pouch

The superficial perineal pouch works in close coordination with the deep perineal pouch to support the urogenital structures and maintain the function of the pelvic floor.

• Erection and Sexual Function:The superficial perineal pouch houses the erectile tissues and muscles that contribute to sexual function, while the deep perineal pouch contains structures that provide neurovascular supply to these tissues. The two pouches work together to ensure proper blood flow, innervation, and support for the external genitalia during sexual activity.
• Urinary Continence:The deep perineal pouch contains muscles that control the urethra, such as the external urethral sphincter, while the muscles in the superficial perineal pouch assist in controlling the flow of urine. Together, these pouches help maintain urinary continence and prevent involuntary leakage.

Clinical Significance

The superficial perineal pouch is important in both sexual and urinary functions, and its involvement in various conditions can lead to significant clinical issues. Trauma, surgery, or infections in this region can affect its contents, leading to complications.

• Trauma and Surgical Injury: Injuries or surgeries in the perineal region can damage the muscles, erectile tissues, or neurovascular structures in the superficial perineal pouch. This can result in sexual dysfunction, such as erectile dysfunction in males or impaired clitoral function in females, and issues with urinary continence.
• Abscesses and Infections: Infections such as perineal abscesses can develop within the superficial perineal pouch, often spreading from neighboring structures. These abscesses may require drainage to prevent further complications.
• Damage During Childbirth (Females): In females, the superficial perineal pouch can be affected during childbirth, particularly if there are tears or episiotomies involving the perineal body. This may lead to pelvic floor dysfunction or sexual difficulties post-delivery.