Penile and Foreskin Neurology: Circumcision is quite damaging

Ken McGrath discusses his research into the neural anatomy of the human penis and the physical damages caused by circumcision. He is:

  • A Senior Lecturer in Pathology at the Faculty of Health, Auckland Uni­versity of Technology

  • A member of the New Zealand Institute of Medical Laboratory Scientists.

  • Author of The Frenular Delta: A New Preputial Structure, published in:

    Understanding Circumcision: A Multi‑Disciplinary Approach to a Multi-Dimensional Problem, Proceedings of the Sixth International Symposium on Genital Integrity: Safeguarding Fundamental Human Rights in the 21st Century, held 2000 December 7–9 in Sydney, Australia.

(slightly modified)

My field of study is anatomy; I teach pathology as it happens, but anatomy is my training.

My interest [in the foreskin] is because New Zealand [at one point] had a very high rate of circumcision, and it seemed to be a very anomalous practice to me—personally and collectively. So, I got a bit curious (as most boys do) as to why this was happening, and I began studying it quite early in my life, as it happens. The more I looked into it, the more anomalous and senseless it seemed to be; it didn't seem to have a medical purpose to it.

[To study tissue in detail], we have to use histological methods. Now, histology is a branch of pathology, which looks at tissue in its natural form; [the term] comes from the Greek meaning “web” or “net” or “fabric”. So, you slice tissue up into very thin [slices], put [them] on slides, and look down the microscope to interpret the arch­itecture of the cells (how they're lined up); most people are familiar with the general pictures of how the skin is arranged and so on, and that's how it's done: You have to take your two-dimensional images that you see on the microscope and build up a three-dimensional image of it. Things have progressed, of course, considerably in recent years[.] Using computer technology and confocal microscopes, [we can now] allow the microscopes to do that [work], and build absolutely exquisite three-dimensional pictures of tissues.

Well, the thing that struck me about [foreskin tissue is its] similarity [to] the finger tip—with the high level of innervation (lots of sensory tissue), and the fact that [the foreskin is] far more complicated than just a simple extension of the shaft skin of the penis, which is what most people say it is (“It's [just] a flap extended over the glans [(the penis head)] to protect the glans”). It is not. I would regard [the foreskin] as an organ in its own right because it has at least two major functions:

  • The first function is mechanical; [the foreskin] provides a rolling bearing on the penis which you wouldn't have otherwise. It also provides the "extra" tissue required for changes in size—the penis does get bigger—and if the skin [were] a fixed size, then a good deal of discomfort would result [with] the huge amount of stretching to accommodate the doubling in size that occurs with erection. So, the foreskin provides accommodation.

  • The second major function is its sensory function; it has become very evident to us over the last 15 years or so—[since] John Taylor and his team came out with the findings in [1996]. The realization has come upon us even if people didn't stop to think about what they were feeling themselves (if they were intact)—I certainly didn't; I didn't really sit down to analyze what I was feeling, but the microscope disclosed to us that the foreskin is heavily sensory in its function. I would believe—well, it is my belief—that [the foreskin] has the highest concentration of sensory nerve endings anywhere on the male body.

So, [the foreskin] can't be ignored; [the foreskin] can't be described as “a simple piece of skin.”

Males and females develop from the same embriological tissue. [There are] two possible pathways [along which] that tissue can develop: Males go down one path under the influence of testosterone, and females go down the other without testosterone.

Most embriologists would say that there are distinct analogs between [male and female genitalia]: The labial tissues, for instance, are said to be the analog of the scrotum, and of course the penis itself has its analog in the clitoris. The foreskin has its analog also in the female; there is a female foreskin: The clitoral hood. The difference—and this is one of the great mysteries of anatomy—is that the male has the nerve endings arranged differently [compared to the female]. It is the human male that is extraordinary and unique; we do not even have the same arrangement as other primates—chimpanzee[s] (our nearest cousins, if you will) do not have the same nerve arrangement on the penis that we do; it's the reverse, in fact. So, humans have developed a penis that's utterly unique, and the thing that fascinates me is that it's been done in such a short period of time—about 4.5 to 5 million years of evolution, which is but a blink of an eye. So, there are great mysteries with the human penis.

The specialized sensory tissue that I've been describing is really quite fascinating. The skin of the penis is zipped up (just like an ordinary zip) on the underside [of the penis] as the layers of cells develop in the embryo; we call [that] the raphae—that little line, the seam which goes up. At the top of the penis, it becomes the little bridge—the frenulum, which is Latin meaning “a little bridle”; “frenum” [means] “bridle” (a horse's bridle), and a frenulum is a little bridle [in that] it tethers the foreskin onto the base of the glans on the underside.

Now, for many years, people thought that [this frenulum is] the only real specialization that had occurred—that it [is] a leftover of this process of zipping all the skin up as it [is] developed, but now we've realized that [the foreskin's] amazing concentration of nerve endings is related to that frenulum: From the frenulum, draping away to each side [of the penis], is a band of ridges—folds in the skin, which John Taylor has called the ridged band. There are about 11 or 12 ridges, and they are very similar to the ridges on the fingers (on the finger tip), and they run right around the entire diameter of the penis and rise up into the frenlum and then close in the inner foreskin [as] a delta triangle of skin, which we've called the frenular delta, [which is] below the frenulum [and] which is exquisitely innervated; most men know this as their own “G-spot”, the spot that is the most sensitive area of the penis.

In that area (in the ridged band and in the frenular delta) we have the same specialist nerve endings that we have in the finger tip, only we have probably 10 times as many [in the foreskin] I would believe (the number hasn't been accurately counted yet, but the number of nerve bundles that wire them up is known and it's very impressive). So, the foreskin is undoubtedly the main sensory unit of the penis. When it is removed, you remove at least 50% of the sensory capacity, so the effect is devastating to the sexual capacity of the organ, as has been well known for centuries.

So, [the foreskin is] a fascinating organ from the neurological point of view, and this specialized arrangement is why you cannot regard the foreskin as “just ordinary skin”. It isn't; [the foreskin is] highly specialized, and therefore, because of the two functions that I've mentioned, it is an organ in its own right.

Well, circumcision by its very nature removes 50% of the skin of the penis, because 50% of the skin is involved in the foreskin; it's a substantial piece of skin—the size of an index card, effectively, in the adult. That amount of skin that's removed includes all of the ridged band and most of the frenular delta. The frenulum may or may not be removed; some surgeons believe it's a nuisance and [that it] should be “extirpated”, as they say—“wiped out”. Others would leave it alone, and those [who] leave it alone leave some of the frenular delta behind and therefore some of the "G-spot", but those [who] completely destroy it take away all of the specialized sensory tissue.

Now, [when this] large number of nerve bundles that supply those nerve endings are cut through [during circumcision], you have the standard response of cut axons (or “wires” in the neural system): The sensory neurons [at the spinal cord] have to try [to do] some sort of damage control. If you cut an area of your skin—and you cut through some nerve bundles—then the nerve cells attempt to re-bridge (to go back to where they were originally), and there's a well-known, well-characterized process for that happening: They send out growth cones from the stump [to seek] where they were originally connected; the downstream portion of the nerve from the cut [is] of course disconnected from the cell and therefore its support (it becomes necrotic and is cleaned up by the immune system and taken away). Now, in the case of something like [circumcision] (where you have chopped out a major piece of skin), the target area—in other words, the nerve endings [to which] those wires (the axons) had originally gone—have now been removed, so [the wires] cannot find where their original end point was: The growth cones go out, come up against the scar tissue (which they cannot penetrate), and they then either die back completely or they get into a knot of growth cones, and all that [such a knot] can transmit is pain; they're known as pain neuroma of scar tissue.

Now, circumcision removes 50% of the skin of the penis—unfortunately, the most important part of the skin: The functional end, not the base where it doesn't matter. [Circumcision] removes something greater than 50% of the sensory nerve endings because they're concentrated in the [ridged band] and [frenular] delta, which [are] automatically destroyed [by] circumcision; we're probably safer to think that it's closer to 75% to 80% of the sensory tissue [that] is lost.

Now, the functional effect of [this destructive surgery] is that the sensory drive into the spinal cord and up into the central nervous system is then greatly reduced:

  • So, not only does the man not feel too much sensation, [but also] many circumcised men do not know where their organsm is—they do not have enough pre‑orgasmic sensation to know how the rise of sensation is proceeding, and orgasm in many of these men comes upon them by surprise, more or less.

  • [Normally], the pain and temperature [sensation]—the very simple and protective and rather unpleasant sensation that comes from the glans when it's at rest—is turned off by [the stimulation of the] foreskin because of inhibitory interneurons in the spinal cord. So, in other words, when you have enough cascade of sensation driving into the [spinal] cord [from the foreskin], it sets off inhibitory interneurons which turn off and inhibit the input from the glans, so [that] men don't feel anything in the glans (because they wouldn't want to [feel such sensation during sexual intercourse]).

    What happens then in the circumcised man?

    When orgasm occurs and [his remaining] foreskin sensory drive begins to tail off, there isn't enough of it—less than 50% of it, of course; there isn't enough of it to maintain the inhibition of the glans, and suddenly [he feels] the most unpleasant sensation in the glans and [he wants] instant stop of motion; [he has] either withdrawn from [his] partner, or if [he's] still inserted, [he says]:

    For heaven's sake, stop! Don't move! I can't bear it!

    This is a very common feature in circumcised men, and it must be devastating for their partners to suddenly have this disconnect of what should be the most joyous moment.

    It's always been a difficulty for me to understand exactly what's been going on, but this is how we believe that [this kind of dyspareunia] (pain of intercourse) [comes about], and it's almost invariably confined to circumcised men—it does appear in intact men when the foreskin is not as mobile as it should be.

What about circumcised men who say "I couldn't deal with any more sensation"?

I think when they're saying that, they're talking of the sensation that's coming from the glans, and the glans does not have the neural equipment to send fine‑touch sensation; it only sends free‑nerve‑ending sensation—in fact, it's nearest equivalent is the cornea of the eye. You don't like stroking the cornea of the eye at all! If you have an eyelash get under the eyelid, you know it's there, but you don't know exactly where it is, and it's dreadfully upsetting, and you want to go and get it cleared—that is what the glans produces: You don't know exactly where [the sensation] is, because it's not actually a high‑resolution system, [and] it's very unpleasant, [but as just described], that [is supposed to get] turned off when a man is in the pre‑orgasmic phase. So, we've got a mechanism in normal intact men for taking away this protective sensation when you don't need it (during sexual intercourse). But, in circumcised men, it returns at the wrong moment.

Well, the natural end to this—to avoid nerve damage, and the loss of sensation and a lifetime of erotic pleasure, and the avoidance of this peculiar pain effect, and so on—is not to cut them in the first place. Just leave it alone! Of course, evolution has actually figured the right pathway: Boys are being born every minute and second of the day complete with foreskins, and they're going to continue to be born with foreskins.


  1. Couple of typos in the transcript, but invaluable analysis, nonetheless! Thank you for posting!

    ("bridal" should be "bridle", "bare" -> "bear")

    1. Thanks! I fixed the typos (and hopefully didn't introduce any new ones in the process!).

  2. great elaboration on the the post-orgasmic sensitivity spike in cut men, studying the nervous system myself I found this quite interesting and parallel to my preconceived suspicions.