Pudendal nerve
Encyclopedia
The pudendal nerve is a sensory and somatic nerve
in the pelvic region which is a large branch of the sacral plexus (L4-5, S1-4) that innervates the external genitalia of both sexes, as well as sphincters for the bladder
and the rectum
. It originates in Onuf's nucleus
in the sacral
region of the spinal cord
.
; it derives its fibers from the ventral rami of the second, third, and fourth sacral nerves (S2, S3, S4).
It passes between the piriformis and coccygeus muscles and leaves the pelvis through the lower part of the greater sciatic foramen
.
It crosses the spine of the ischium, and reenters the pelvis
through the lesser sciatic foramen
.
It accompanies the internal pudendal vessels upward and forward along the lateral wall of the ischiorectal fossa
, being contained in a sheath of the obturator fascia termed the pudendal canal
.
The pudendal nerve gives off the inferior rectal nerves. It soon divides into two terminal branches: the perineal nerve
, and the dorsal nerve of the penis
(in males) or the dorsal nerve of the clitoris (in females).
Research shows that variations in pudendal nerve origin are possible. For example, the pudendal nerve may actually originate off of the Sciatic nerve
. Consequently, damage to the sciatic nerve can affect the pudendal nerve as well.
and clitoris
, bulbospongiosus
and ischiocavernosus muscle
s, and areas around the scrotum
, perineum
, and anus
. At sexual climax, the spasm
s in the bulbospongiosus and ischiocavernous results in ejaculation
in the male and most of the feelings of orgasm
in both sexes.
or bicycling can compress or stretch the pudendal nerve, causing temporary loss of function, but permanent injury is rare. Entrapment
of the nerve is very rare but can happen. A pelvic tumor (most notably a large sacrococcygeal teratoma
), or surgery to remove the tumor, can damage this nerve permanently. A pudendal nerve block is a common obstetric procedure to anesthetize the perineum during labor.
in females), pelvic and anorectal pain In rare cases, the nerve may be destroyed with either alcoholic or radiofrequency ablation.
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
in the pelvic region which is a large branch of the sacral plexus (L4-5, S1-4) that innervates the external genitalia of both sexes, as well as sphincters for the bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
and the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
. It originates in Onuf's nucleus
Onuf's nucleus
Onuf’s nucleus is a distinct group of neurons located in the ventral part of the anterior horn of the sacral region of the human spinal cord involved in the maintenance of micturition and defecatory continence, as well as muscular contraction during orgasm. It contains motor neurons, and is the...
in the sacral
Sacral
Sacral may refer to:*sacred*sacrum...
region of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
.
Anatomy
The pudendal nerve originates in the sacral plexusSacral plexus
-External links:*...
; it derives its fibers from the ventral rami of the second, third, and fourth sacral nerves (S2, S3, S4).
It passes between the piriformis and coccygeus muscles and leaves the pelvis through the lower part of the greater sciatic foramen
Greater sciatic foramen
-Boundaries:It is bounded as follows:* anterolaterally by the greater sciatic notch of the illium* posteromedially by the sacrotuberous ligament* inferiorly by the sacrospinous ligament and the ischial spine* superiorly by the anterior sacroilliac ligament...
.
It crosses the spine of the ischium, and reenters the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
through the lesser sciatic foramen
Lesser sciatic foramen
An opening between the pelvis and the posterior thigh, the foramen is formed by the sacrotuberous ligament which runs between the sacrum and the ischial tuberosity and the sacrospinous ligament which runs between the sacrum and the ischial spine.-Boundaries:...
.
It accompanies the internal pudendal vessels upward and forward along the lateral wall of the ischiorectal fossa
Ischiorectal fossa
The ischioanal fossa is somewhat prismatic in shape, with its base directed to the surface of the perineum, and its apex at the line of meeting of the obturator and anal fasciae.-Boundaries:...
, being contained in a sheath of the obturator fascia termed the pudendal canal
Pudendal canal
The pudendal canal is an anatomical structure in the pelvis through which the internal pudendal artery, internal pudendal veins, and the pudendal nerve pass.-Structure:...
.
The pudendal nerve gives off the inferior rectal nerves. It soon divides into two terminal branches: the perineal nerve
Perineal nerve
The perineal nerve is a nerve arising from the pudendal nerve that supplies the perineum.-Structure:The perineal nerve is the inferior and larger of the two terminal branches of the pudendal nerve, is situated below the internal pudendal artery....
, and the dorsal nerve of the penis
Dorsal nerve of the penis
The dorsal nerve of the penis is the deepest division of the pudendal nerve; it accompanies the internal pudendal artery along the ramus of the ischium; it then runs forward along the margin of the inferior ramus of the pubis, between the superior and inferior layers of the fascia of the...
(in males) or the dorsal nerve of the clitoris (in females).
| Branch | Description >- | Inferior anal nerves Inferior anal nerves The Inferior rectal nerves usually branch from the pudendal nerve but occasionally arises directly from the sacral plexus; they cross the ischiorectal fossa along with the inferior hemorrhoidal vessels, toward the anal canal and the lower end of the rectum, and is distributed to the Sphincter ani... |
Greater sciatic foramen Greater sciatic foramen -Boundaries:It is bounded as follows:* anterolaterally by the greater sciatic notch of the illium* posteromedially by the sacrotuberous ligament* inferiorly by the sacrospinous ligament and the ischial spine* superiorly by the anterior sacroilliac ligament... . >- | Perineal nerve Perineal nerve The perineal nerve is a nerve arising from the pudendal nerve that supplies the perineum.-Structure:The perineal nerve is the inferior and larger of the two terminal branches of the pudendal nerve, is situated below the internal pudendal artery.... |
>- | deep perineal pouch Deep perineal pouch The deep perineal pouch is a human anatomical term that refers to the space enclosed in part by the perineum, and located superior to the perineal membrane.-Structure:... >- |Posterior scrotal nerves Posterior scrotal nerves The posterior scrotal branches or ""posterior labial branches"" are two in number, medial and lateral. They are branches of the perineal nerve, which is itself is a branch of the pudendal nerve... /Posterior labial nerves Posterior labial nerves The posterior labial nerves are branches of the pudendal nerve.The counterparts in males are the posterior scrotal nerves.-External links: - "The Female Perineum: Muscles of the Superficial Perineal Pouch" - "Inferior view of female perineum, branches of the internal pudendal artery."... |
Posterior scrotum/Posterior labia |
Research shows that variations in pudendal nerve origin are possible. For example, the pudendal nerve may actually originate off of the Sciatic nerve
Sciatic nerve
The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...
. Consequently, damage to the sciatic nerve can affect the pudendal nerve as well.
Physiology
The pudendal nerve innervates the penisPenis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
and clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...
, bulbospongiosus
Bulbospongiosus muscle
Bulbospongiosus is one of the superficial muscles of the perineum. It has a slightly different origin, insertion and function in males and females. In males, it covers the bulb of the penis...
and ischiocavernosus muscle
Ischiocavernosus muscle
The ischiocavernosus muscle is a muscle just below the surface of the perineum, present in both men and women.-Function:It helps flex the anus, and stabilize the erect penis or tense the vagina during orgasm...
s, and areas around the scrotum
Scrotum
In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...
, perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
, and anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
. At sexual climax, the spasm
Spasm
In medicine a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. It is sometimes accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes...
s in the bulbospongiosus and ischiocavernous results in ejaculation
Ejaculation
Ejaculation is the ejecting of semen from the male reproductory tract, and is usually accompanied by orgasm. It is usually the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases ejaculation occurs because of prostatic disease...
in the male and most of the feelings of orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...
in both sexes.
Pathology
Difficult childbirthChildbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
or bicycling can compress or stretch the pudendal nerve, causing temporary loss of function, but permanent injury is rare. Entrapment
Pudendal nerve entrapment
Pudendal nerve entrapment , also known as Alcock canal syndrome, is an uncommon source of chronic pain, in which the pudendal nerve is entrapped or compressed. Pain is positional and is worsened by sitting...
of the nerve is very rare but can happen. A pelvic tumor (most notably a large sacrococcygeal teratoma
Sacrococcygeal teratoma
Sacrococcygeal teratoma is a teratoma located at the base of the coccyx . It is thought to be a derivative of the primitive streak.-Natural history:...
), or surgery to remove the tumor, can damage this nerve permanently. A pudendal nerve block is a common obstetric procedure to anesthetize the perineum during labor.
Radiology
The pudendal nerve is difficult to visualize on routine CT or MR imaging, however under CT guidance, a needle may be placed adjacent to the pudendal neurovascular bundle. The ischial spine, an easily identifiable structure on CT, is used as the level of injection. A spinal needle is advanced via the gluteal muscles and advanced within several millimeters of the ischial spine. Contrast (X-ray dye) is then injected, highlighting the nerve in the canal, confirming correct needle placement. The nerve may then be injected with cortisone and local anaesthetic to confirm and also treat chronic pain of the external genitalia (known as vulvodyniaVulvodynia
Vulvodynia is a chronic pain syndrome that affects the vulvar area and occurs without an identifiable cause or visible pathology categorized in the ICD-9 group 625—specifically ICD-9 625.7, which is for pain and other disorders of the female genital organs...
in females), pelvic and anorectal pain In rare cases, the nerve may be destroyed with either alcoholic or radiofrequency ablation.