Clitoris: How many nerve fibers does it really have?
- Researchers sought to quantify the number of nerve fibers that innervate the human clitoris by analyzing samples of clitoral nerve tissue from human volunteers.
- They found that the human clitoris contains 10,281 nerve fibers on average, which exceeds a previous estimate based on a study in cows.
- A better understanding of human clitoral innervation has ramifications for many areas of medical practice, including gender-affirming surgery and repair of the dorsal clitoral nerve after genital mutilation or surgical injury.
The clitoris — a pleasure-producing sexual organ that is located where the labia minora (inner lips) meet and extends along both sides of the vagina — is the female equivalent of the penis.
In fact, the clitoris originates from the same mass of tissue in the embryo that gives rise to the penis.
Although it carries the same importance in sexual functioning, the clitoris has been less widely studied than its male counterpart.
Overturning outdated assumptions
Researchers are aware that the clitoris has a substantial supply of nerves — cordlike structures composed of nerve fibers (or axons) — that conduct signals between the brain and spinal cord and other parts of the body.
However, the number of nerve fibers within the human clitoris has never been officially quantified. The most often-cited claim is that the clitoris has “8,000 nerve endings,” but this figure originates from a bovine study mentioned in a book titled The Clitoris, which appeared in 1976.
To rectify this outdated piece of essential information, a study led by the Oregon Health & Science University (OHSU) examined tissue samples of the dorsal nerve of the clitoris in an effort to quantify the number of nerve fibers innervating the human clitoris.
The dorsal nerve, which consists of two symmetrical, tube-like structures, is the main nerve responsible for clitoral sensation.
The researchers presented the results of this first known count of human clitoral tissue at a scientific conference hosted by the Sexual Medicine Society of North America and the International Society for Sexual Medicine on October 27, 2022. A detailed paper explaining the study will appear in the Journal of Sexual Medicine.
“[T]his [study] highlights the broad scope of knowledge gaps that are present within vulvar health. These fundamental gaps […] ultimately do result in significant consequences for patients,” Dr. Maria Uloko, study co-author and assistant professor of urology at the University of California, San Diego, told Medical News Today.
“There are numerous statistics regarding the difficulty of access to care for common vulvar conditions, [which] lead to significant healthcare cost[s] to patients as well as the healthcare system. We are talking [about] billions of dollars spent on vulvar and urinary conditions alone. And the societal cost of the psychological symptoms associated with just trying to get a diagnosis really can’t be quantified but they are quite high. This research is the start of reassessing what we know about the vulva and filling in those knowledge gaps.”
– Dr. Maria Uloko
The researchers obtained clitoris tissue samples from seven transmasculine volunteers who were undergoing a gender-affirming surgical procedure known as phalloplasty.
During a phalloplasty, surgeons use tissues taken from the person’s clitoris and other body parts to construct a functional penis.
The researchers looked at one half of the dorsal nerve, magnifying it 1,000 times under a microscope, and used image analysis software to count the individual nerve fibers.
In each sample, they found 5,140 nerve fibers on average. Since the dorsal clitoral nerve is symmetrical, they multiplied this number by two, concluding that the average dorsal nerve of the clitoris contains 10,281 nerve fibers, with a possible count ranging from 9,852 to 11,086.
This result is about 20% higher than the conventional estimate of 8,000 nerve fibers.
To put the findings in perspective, study coauthor Dr. Blair Peters, an assistant professor of surgery at the OHSU School of Medicine and a plastic surgeon who specializes in gender-affirming care, notes that:
“Even though the hand is many, many times larger than the clitoris, the median nerve [which runs through the wrist and hand] only contains about 18,000 nerve fibers, or fewer than two times the nerve fibers that are packed into the much-smaller clitoris.”
The researchers believe that establishing the number of fibers in the dorsal clitoral nerve is an important step in the understanding of clitoral innervation and sexual response.
It should also draw attention to the need for more education, research, and funding attributed to studying the clitoris.
“Importantly, there are few options available to people who have suffered nerve damage to the clitoris and researchers should build on this work to be able to better treat these conditions. It should [equally] importantly be seen that this work came from trans people and is for people of all genders,” Dr. Peters told MNT.
One field that will benefit from the results of this study is clitoral reconstruction following female genital mutilation (FGM). There have been several reports of injury to the clitoris and its nerves as a result of FGM.
The researchers hope that their findings will lead to new surgical techniques to repair injured nerves.
Dr. Bahir Edouard Elias, a plastic, esthetic and reconstructive surgeon specializing in the field of surgical reconstruction after FGM, who did not contribute to the current research, told MNT that this “excellent study […] will be of great help” in that area.
Dr. Peters believes that the results of this study will improve sensory outcomes for transgender patients undergoing phalloplasty as the surgeon can better select which nerves to connect during the procedure.
The researchers are also hopeful that their findings could help reduce accidental nerve injuries during elective female genital cosmetic surgery. However, Dr. John G Hunter, professor of clinical surgery at Weill Cornell Medicine and attending plastic surgeon at New York-Presbyterian Hospital, expressed some skepticism in his comments to MNT.
“As [a] surgeon who has performed over 1,000 labiaplasties, with clitoral hood alteration in approximately half, my patients virtually never report negative ‘sexual function’ consequences from the procedure postoperatively,” he said.
“This is supported by published literature. But this is subjective, and follow-up is rarely longer than 4–6 months for labia minora (inner lip) reduction. Gender-reaffirming surgery is entirely different. It also includes much more psychological overtones,” he added.
According to Dr. Hunter, “[m]ore studies are needed, but [it is uncertain] that one will ever be able to correlate gross anatomical findings with functional — especially erotic/ sensory — findings in genital anatomy.”
When asked about the study’s limitations, Dr. Peters noted that the study had a small cohort and only one sample was collected from each participant.
Furthermore, all participants were on testosterone therapy. While hormone therapy should not impact nerve fiber count, the analysis of tissue samples from individuals who are not on exogenous hormones would support the study.
Another limitation, Dr. Peters pointed out, is that “the total number [of nerve fibers] was calculated assuming bilateral symmetric innervation” — that is, that the dorsal nerve is symmetrical.
The researchers also noted that the study focuses on myelinated nerve fibers in the dorsal clitoral nerve. Since unmyelinated nerve fibers and other nerves in the clitoris were not counted, the result of this study likely underestimates the number of nerve fibers in the human clitoris.
In the future, Dr. Peters would like to conduct similar studies on the penis glans (or head), with the hope of shedding more light on the two organs and aiding surgeons in creating a functional clitoris for transgender patients.
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