Internal pudendal artery

The internal pudendal artery is a major branch of the internal iliac artery that supplies blood to the perineum and external genitalia. It plays a vital role in providing oxygenated blood to the muscles and tissues of the pelvic region.

Location

The internal pudendal artery originates from the internal iliac artery in the pelvic region. It exits the pelvis through the greater sciatic foramen, passing between the piriformis muscle and the coccygeus muscle. It then curves around the sacrospinous ligament and re-enters the pelvis through the lesser sciatic foramen. From here, the artery travels through the pudendal canal (Alcock’s canal) alongside the pudendal nerve and supplies the perineum, external genitalia, and anal canal. Along its course, it gives off several important branches, including the inferior rectal artery, perineal artery, and dorsal artery of the penis or clitoris.

Structure and Anatomy

Origin

The internal pudendal artery arises from the anterior division of the internal iliac artery, one of the two terminal branches of the common iliac artery. The internal iliac artery supplies the pelvic organs, and the internal pudendal artery specifically supplies structures in the perineum and external genitalia. The internal pudendal artery is one of several important branches from the internal iliac artery, including the superior and inferior gluteal arteries, obturator artery, and middle rectal artery.

Course

The internal pudendal artery has a complex course as it exits and re-enters the pelvis. It follows this pathway:

• Exits the Pelvis through the Greater Sciatic Foramen: After originating from the internal iliac artery, the internal pudendal artery exits the pelvis through the greater sciatic foramen, which is a large opening located between the ischium and sacrum. The artery passes below the piriformis muscle, alongside the pudendal nerve and the inferior gluteal artery.
• Curves Around the Sacrospinous Ligament: After exiting the pelvis, the internal pudendal artery passes around the sacrospinous ligament, which runs between the ischial spine and the sacrum. This curve allows the artery to re-enter the pelvis and enter the perineal region.
• Re-Enters the Pelvis through the Lesser Sciatic Foramen: The internal pudendal artery re-enters the pelvis through the lesser sciatic foramen, located below the greater sciatic foramen. This foramen is bordered by the sacrospinous ligament (superiorly) and the sacrotuberous ligament (posteriorly).
• Travels through the Pudendal Canal (Alcock’s Canal): Once the artery re-enters the pelvis, it travels through the pudendal canal (Alcock’s canal), which is a fibrous canal formed within the obturator fascia on the lateral wall of the ischioanal fossa. The pudendal canal carries the internal pudendal artery, pudendal vein, and pudendal nerve to the perineum.

Branches

The internal pudendal artery gives rise to several important branches that supply the perineum, external genitalia, and rectal region:

• Inferior Rectal Artery: This artery branches off early as the internal pudendal artery enters the ischioanal fossa. It travels medially toward the anal canal and supplies blood to the lower rectum and anal canal, as well as the external anal sphincter. The inferior rectal artery also anastomoses with the superior and middle rectal arteries.
• Perineal Artery: This branch supplies the perineal muscles and the skin of the perineum. It also gives off posterior scrotal arteries (in males) or posterior labial arteries (in females) that provide blood to the scrotum or labia majora, respectively.
• Arteries to the External Genitalia:
• • In males, the internal pudendal artery gives rise to the artery of the bulb of the penis, the deep artery of the penis, and the dorsal artery of the penis, which are critical for supplying the erectile tissues and skin of the penis.
  • In females, it gives rise to the artery of the bulb of the vestibule, the deep artery of the clitoris, and the dorsal artery of the clitoris, which supply the erectile tissues and skin of the clitoris and vestibule.
• Posterior Scrotal/Labial Arteries: These branches supply the posterior part of the scrotum in males or the labia majora in females. They arise from the perineal artery and provide vascularization to the skin and fascia of these external genital structures.

Termination

The internal pudendal artery terminates by dividing into the dorsal artery of the penis (in males) or the dorsal artery of the clitoris (in females). These terminal branches run along the dorsal aspect of the penis or clitoris, supplying the erectile tissues, corpus cavernosum, and skin of the external genitalia. The dorsal artery of the penis or clitoris is essential for providing blood to these structures during arousal and sexual function.

Anatomical Relations

• Pudendal Nerve: The internal pudendal artery runs alongside the pudendal nerve, which is responsible for motor and sensory innervation of the perineum and external genitalia. Both the artery and nerve travel together through the greater sciatic foramen, pass around the sacrospinous ligament, and enter the pudendal canal together. Their close anatomical relationship is important for coordinating blood supply and nerve signals to the pelvic and perineal structures.
• Piriformis Muscle: As the internal pudendal artery exits the pelvis through the greater sciatic foramen, it passes just inferior to the piriformis muscle, a muscle of the gluteal region that helps rotate the thigh.
• Levator Ani and Coccygeus Muscles: The internal pudendal artery runs close to the levator ani and coccygeus muscles, which are part of the pelvic diaphragm that supports the pelvic organs. These muscles help maintain continence and support the rectum and anal canal.
• Sacrospinous Ligament: The internal pudendal artery curves around the sacrospinous ligament, which extends from the ischial spine to the sacrum. This relationship is important during surgical procedures involving the pelvic region, as the artery must be carefully avoided when manipulating the ligaments.

Surface Anatomy and Palpation

While the internal pudendal artery is located deep within the pelvis and perineum, its branches, such as the dorsal artery of the penis or clitoris, become more superficial and can be identified during clinical examinations. For example, the dorsal artery of the penis can be palpated along the dorsal aspect of the penis, particularly during arousal when the blood supply increases.

Function

Primary Blood Supply to the Perineum

The internal pudendal artery is the primary artery responsible for supplying oxygenated blood to the perineum, which includes the muscles, skin, and connective tissues of the urogenital triangle and anal region. By delivering blood to these vital structures, the internal pudendal artery ensures proper functioning of the perineal muscles, which play roles in sexual activity, continence, and supporting the pelvic organs. The perineal region relies on this artery for maintaining tissue viability and integrity.

Blood Supply to the Anal Canal and Sphincter Muscles

The internal pudendal artery provides critical blood flow to the anal canal and external anal sphincter through its branch, the inferior rectal artery. This artery supplies blood to the anal mucosa, external anal sphincter, and perianal skin, which are necessary for maintaining continence and facilitating proper defecation. The oxygen and nutrients delivered by the artery ensure the health of the anal tissues, especially the sphincter muscles, which require a constant blood supply to function correctly. Adequate vascularization also supports the healing of the anal canal in cases of injury or surgery.

Blood Supply to the External Genitalia (in Males and Females)

The internal pudendal artery provides a direct blood supply to the external genitalia through several key branches, which differ between males and females:

In Males:

• Artery of the Bulb of the Penis: This artery supplies blood to the bulbospongiosus muscle and the bulb of the penis, the proximal part of the corpus spongiosum that surrounds the urethra.
• Deep Artery of the Penis: This artery supplies the corpus cavernosum, the erectile tissue responsible for penile rigidity during erection.
• Dorsal Artery of the Penis: This artery runs along the dorsal surface of the penis, supplying blood to the skin and fascia, and supporting erectile function by delivering oxygenated blood to the tissues involved in sexual arousal.

In Females:

• Artery of the Bulb of the Vestibule: This artery supplies blood to the bulbospongiosus muscle and the bulb of the vestibule, which are involved in female sexual arousal.
• Deep Artery of the Clitoris: This artery provides blood to the corpus cavernosum of the clitoris, contributing to the erectile function of the clitoris.
• Dorsal Artery of the Clitoris: This artery supplies the skin and erectile tissues of the clitoris, supporting its function during sexual arousal.

In both males and females, the blood supplied by the internal pudendal artery is essential for maintaining the health of the erectile tissues, which fill with blood during sexual arousal, allowing for proper erectile function in both the penis and clitoris.

Blood Supply to the Perineal Muscles

The internal pudendal artery supplies blood to the perineal muscles, including the ischiocavernosus, bulbospongiosus, and superficial transverse perineal muscles. These muscles play key roles in supporting the pelvic floor, maintaining continence, and assisting in sexual functions:

• Ischiocavernosus Muscle: This muscle compresses the base of the penis or clitoris, helping to maintain an erection by reducing venous outflow from the erectile tissues.
• Bulbospongiosus Muscle: In males, this muscle aids in the expulsion of semen during ejaculation. In females, it contributes to the constriction of the vaginal orifice and supports the clitoris during arousal.
• Superficial Transverse Perineal Muscle: This muscle helps stabilize the perineal body, which is a central point in the pelvic floor that provides structural support to the pelvic organs.

The internal pudendal artery ensures that these muscles receive the oxygen and nutrients they need to function properly during physical and sexual activity.

Support for Pelvic Floor Function

The internal pudendal artery indirectly supports the pelvic floor by supplying blood to the levator ani muscle and the surrounding perineal structures. The pelvic floor is a muscular sheet that supports the bladder, uterus, and rectum, and its proper function is critical for maintaining continence and supporting the pelvic organs. By providing blood to the perineum and pelvic muscles, the internal pudendal artery plays a key role in pelvic floor health, helping to prevent pelvic organ prolapse and incontinence.

Blood Supply to the Scrotum and Labia Majora

Through its branches, such as the posterior scrotal arteries in males and posterior labial arteries in females, the internal pudendal artery supplies blood to the scrotum and labia majora, respectively. These structures require proper blood flow for maintaining tissue health and performing their functions:

• In Males: The posterior scrotal arteries provide blood to the scrotal skin and underlying tissues, ensuring proper regulation of testicular temperature, which is crucial for spermatogenesis.
• In Females: The posterior labial arteries supply blood to the labia majora, contributing to the vascularization of the external genitalia and supporting their health and function.

Role in Erectile Function

The internal pudendal artery is critical for erectile function in both males and females by supplying blood to the erectile tissues of the penis and clitoris. The deep artery of the penis and dorsal artery of the penis are responsible for filling the corpus cavernosum with blood, which leads to penile erection in males. Similarly, in females, the deep artery of the clitoris and dorsal artery of the clitoris supply the corpus cavernosum of the clitoris, allowing for clitoral erection during sexual arousal. Without adequate blood flow from the internal pudendal artery, erectile dysfunction can occur, resulting in impaired sexual function.

Nutrient and Oxygen Delivery to the Perineal and Genital Tissues

As with all arteries, the internal pudendal artery delivers essential oxygen and nutrients to the tissues it supplies. This oxygenation is crucial for maintaining the health and function of the perineal muscles, skin, and external genitalia. It supports the continuous regeneration of cells and tissues in these areas, ensuring their ability to perform normal functions, such as muscle contraction during continence, erectile function, and the expulsion of waste from the body.

Removal of Metabolic Waste Products

In addition to supplying oxygenated blood, the internal pudendal artery supports the removal of metabolic waste products from the tissues it supplies. During physical activity or sexual function, the perineal muscles and erectile tissues produce metabolic byproducts like carbon dioxide and lactic acid, which must be efficiently removed to prevent fatigue and tissue damage. The blood flow from the internal pudendal artery facilitates the removal of these waste products, ensuring that the tissues remain healthy and capable of performing their functions effectively.

Support for Wound Healing and Tissue Repair

The internal pudendal artery also plays an important role in wound healing and tissue repair. The tissues it supplies, particularly in the perineal and genital regions, are prone to injury during childbirth, sexual activity, or surgery. Adequate blood flow from the internal pudendal artery supports cellular regeneration, collagen production, and healing processes, ensuring that tissues recover properly after injury. This function is crucial for reducing complications such as infection or delayed healing in the perineal region.

Clinical Significance

The internal pudendal artery is critical in supplying blood to the perineum, external genitalia, and anal region, making it essential for functions such as sexual function, continence, and pelvic support. Its role in providing blood to the erectile tissues of the penis and clitoris is crucial for proper erectile function in both males and females. Damage or disruption to this artery, such as during pelvic surgery or trauma, can result in erectile dysfunction, incontinence, or impaired sexual response.

The artery’s involvement in the blood supply to the anal canal and sphincters also makes it essential for maintaining fecal continence. During surgical procedures like hemorrhoidectomy or pudendal nerve blocks, knowledge of the internal pudendal artery’s course is important to avoid excessive bleeding and ensure tissue health. In addition, its role in supporting the perineal muscles and pelvic floor makes it a key vessel in addressing pelvic organ prolapse and recovery from perineal injuries, such as those occurring during childbirth.