Generality
The pudendal nerve is one of the most important nerves originating from the sacral plexus and pudendal plexus.
Belonging to the peripheral nervous system, the pudendal nerve is a mixed nerve, which has the important task of innervating the external genitals of man and woman, the perineum and anus, and of controlling the pelvic floor muscles.
In principle, shortly before the sacrospinous ligament, the pudendal nerve passes between the piriformis and ischiococcygeal muscles, emerges from the pelvis at one point and then returns from another position, takes the so-called pudendal canal and branches off into three branches.
Short review of what a nerve is
To fully understand what a nerve is, it is necessary to start from the concept of neuron .
Neurons represent the functional units of the nervous system . Their task is to generate, exchange and transmit all those (nervous) signals that allow muscle movement, sensory perceptions, reflex responses and so on.
Typically, one neuron consists of three parts:
- The so-called body, where the cell nucleus resides.
- Dendrites, which are equivalent to receiving antennae for nerve signals from other neurons or receptors located in the periphery.
- Axons, which are cellular extensions having the function of spreading the nervous signal. The axon covered with myelin (myelin sheath) is also called nerve fiber.
A bundle of axons forms a nerve .
Nerves can carry information in three ways:
- From the central nervous system (CNS) to the periphery . The nerves with this property are called efferent . The efferent nerves control the movement of the muscles, so I am in charge of the motor sphere.
- From the periphery to the CNS . Nerves with this capacity are called afferent . The afferent nerves signal to the CNS what they detected in the periphery, therefore they cover a sensitive (or sensory) function.
- From the SNC to the periphery and vice versa . Nerves with this double capacity are called mixed . Mixed nerves have a dual function: motor and sensory.
What is Pudendo Nerve?
The pudendal nerve is a mixed nerve, belonging to the peripheral nervous system and known to innervate the external genitals in both men and women, the perineum and the anal region.
The term "even" indicates that the pudendal nerve is present both on the right half of the human body and on the left one.
Anatomy
The pudendal nerve is a derivation of the so-called sacral plexus and the so-called pudendus plexus, which, in order, passes between the piriformis and ischiococcygeal muscles, emerges from the pelvis at one point and then re-enters from another position, takes the so-called channel pudendo and branches out in various branches.
Origin of the Nervo Pudendo: the details
The pudendal nerve results from the union of the nerve roots that derive from the ventral branches of the sacral spinal nerves S2, S3 and S4 ; these nervous structures belong partly to the sacral plexus and partly to the pudendus plexus, which explains why the pudendal nerve appears to be a branch of both.
Located in the posterior part of the pelvis, the sacral plexus and the pudendus plexus are the nerve formations that collect the branches of the ventral branches of the spinal nerves L4 (part), L5, S1, S2, S3 and S4.
Specifically, the sacral plexus comprises: the ventral branches of L4 not belonging to the lumbar plexus, the ventral branches of L5, the ventral branches of S1 and part of the ventral branches of S2 and S3; the pudendus plexus, on the other hand, includes: the ventral branches of S2 and of S3 not belonging to the sacral plexus, and the ventral branches of S4.
The nerve roots that give rise to the pudendal nerve are altogether 3; the exact point where these converge, to give life to the nerve in question, is just before the so-called sacrospinous ligament, the thin ligament of the sacro-iliac joint having the task of opposing the forward inclination of the sacrum.
Curiosity
The ventral branches that give rise to the pudendal nerve belong to a characteristic grouping of neurons in the sacral region of the spinal cord, whose name is Onuf's nucleus (the term "nucleus", in this specific juncture, does not refer to the cell nucleus, but an agglomeration of neurons with a common peculiarity).
Course of Nervo Pudendo: the details
From its origin, the pudendal nerve proceeds downwards, passing between the piriformis and ischiococcygeal muscles, and exits from the pelvis (or pelvis ), exploiting the opening of the so-called large ischial hole.
Its exit from the pelvis is temporary; in fact, after passing through the large ischial hole, the pudendal nerve slightly changes its direction and, in circumventing the aforementioned sacrospinous ligament, re-enters the pelvis, exploiting (this time) the opening of the small ischial hole .
With the return to the pelvis, therefore, it assumes an antero-superior orientation that leads it to accompany, along their path, the internal pudendal artery and the internal pudenda vein and to take, together with the vessels just mentioned, the aforementioned pudendal canal ( or channel of Alcock ).
The pudendal canal is located on the obturator fascia, above the particular ridge present on the ischial tuberosity .
Within the pudendal canal, it branches, giving rise to the so-called pudendal nerve branches .
Brache del Nervo Pudendo: the details
To understand…
The branches of a nerve are its branches and also correspond to nerves.
Inside the pudendal canal, the pudendal nerve gives rise to 3 branches, which, in order of appearance along the path of the nerve in question, are:
- The lower rectal nerve (or lower hemorrhoidal nerve ),
- The perineal nerve e
- The dorsal nerve of the penis (in men) or clitoris (in women).
LOWER RECTAL NERVE
The lower rectal nerve is the first branch of the pudendal nerve.
In making its way to the perineal area and the anal area, this branch of the pudendal nerve forms a sort of arch and passes through the so - called ischio-rectal fossa .
PERINEAL NERVE
The perineal nerve is the branch of the pudendal nerve which represents its direct continuation.
This nervous structure follows a path that leads it, initially, to take the deep perineal sac, remaining immediately below the internal pudendal artery, and, at a later time, to divide into two sub- branches, called the superficial branch of the perineal nerve and deep branch of the perineal nerve .
DORSAL NERVE OF THE PENIS OR CLITORIDE
The dorsal nerve of the penis or clitoris is the branch of the pudendal nerve that runs along the lateral wall of the ischio-rectal fossa, reaches the pubic symphysis and, finally, continues up to the penis, in the man, and up to the clitoris, in the woman .
Report by Nervo Pudendo
In summary, during his journey, the pudendal nerve passes near:
- The piriformis muscle, shortly after the origin and just before leaving the pelvis (through the large ischial hole);
- The sacrospinous ligament, just before re-entering the pelvis (through the small ischial hole);
- The internal pudendal artery and the internal pudendal vein, at the moment when it enters the pudendal canal.
Anatomical variants of Pudendo Nerve
As with many other structures of the human body, anatomical variants also exist for the pudendal nerve, that is slightly different versions of the nerve in question, in terms of anatomy, from what has been reported so far.
The most important variants of the pudendal nerve include:
- The pudendal nerve with origin coupled to the sciatic nerve e
- The pudendal nerve with a contribution of axons originating from the ventral branches of the sacral spinal nerve S5.
Curiosity
In people with the pudendal nerve associated with the sciatic nerve, episodes of inflammation of the sciatic nerve (ie sciatica ) also cause inflammation of the pudendal nerve .
Function
As a mixed nerve, the pudendal nerve covers both motor functions (ie it controls muscles) and sensitive functions (ie it deals with the perceptive cutaneous capacity of some specific areas of the human body).
Motor Functions of the Pudendo Nerve
As far as its motor functions are concerned, the pudendal nerve controls:
- Through the inferior rectal nerve, the external anal sphincter muscle e
- Through the perineal nerve (to be precise the deep branch), the muscles of the perineum and pelvic floor called the bulbospongius muscle, ischiocavernosus muscle and levator ani, and the external urethral sphincter muscle (or external sphincter muscle of the urethra ).
The action of domination on the external anal and external urethral sphincters invests the pudendal nerve of the charge of nerve deputed to the voluntary control of fecal and urinary continence .
Sensitive Functions of Pudendal Nerve
As far as its sensitive functions are concerned, instead, the pudendal nerve controls:
- Through the inferior rectal nerve, the cutaneous sensitivity of the perianal region and the sensitivity in the lower third of the anal canal ;
- Through the perineal nerve (to be precise the superficial branch), the cutaneous sensitivity of the perineum, of the posterior part of the scrotum (in the man) and of the small and large lips (in the woman).
- Through the dorsal nerve of the penis or clitoris, the cutaneous sensitivity of the penis, in men, and of the clitoris, in women.
Did you know that ...
The control of skin sensitivity at the level of the penis or clitoris, exerted by the dorsal nerve of the penis or clitoris, invests this branch of the pudendal nerve with a pivotal role in the mechanism of penis erection, in man, and of erection of the clitoris, in the woman.
diseases
The pudendal nerve can be injured or compressed, which can cause temporary or permanent forms of neuropathy .
With regards to these topics, it is important to note:
- Pudendal nerve injuries are observable conditions especially in people with diabetes or multiple sclerosis.
- The compression of the pudendal nerve at the level of the pudendal canal (in the medical field, the so-called Alcock canal syndrome ) is a rare phenomenon, which however is still of interest, since it mainly affects those who practice cycling at a professional level.
Clinical Use
The pudendal nerve has a role of some relevance also in the clinical-therapeutic field; the pudendal nerve, in fact, serves for the implementation of the so-called pudendal block, a form of anesthesia used during vaginal delivery, episiotomy interventions and other minor vaginal surgery procedures useful to desensitize the skin areas controlled precisely by the pudendal nerve.
In the pudendal block, the injection of the anesthetic - usually lidocaine - takes place in the pudendal nerve tract that passes through the pudendal canal.
