The clitoris is a sexual organ located at the front of the vulva, and its primary function is pleasure. What most people recognize as “the clitoris” is actually just a small visible portion called the glans, a pea-sized nub sitting at the junction where the inner labia meet. But the full structure extends well beneath the skin, with internal components that wrap around the vaginal canal and urethra. It is the most nerve-dense organ in the human body.
More Than What You Can See
The visible part of the clitoris, the glans, is covered by a small fold of skin called the clitoral hood. This is the part most people are referring to when they talk about the clitoris. But the glans is comparable to the tip of an iceberg.
Beneath the surface, the clitoris has a shaft (called the body) that extends upward and then splits into two leg-like structures called crura, which reach back along either side of the vaginal opening. Nearby, a pair of structures called the vestibular bulbs sit along the vaginal walls. Together, these internal and external parts form an interconnected cluster of erectile tissue. MRI imaging by Australian urologist Dr. Helen O’Connell confirmed that the bulbs, body, and crura form a consistent tissue complex that partially surrounds both the urethra and the vagina.
The total structure can extend roughly 9 to 11 centimeters when you include the internal portions, though size varies from person to person. The glans alone is typically only a few millimeters to about a centimeter across.
Why It’s So Sensitive
The glans clitoris is extraordinarily sensitive because of the sheer density of nerve fibers packed into such a small area. A 2023 study was the first to directly count the nerve fibers running through the dorsal nerve of the clitoris in human tissue samples. Researchers found approximately 10,280 myelinated nerve fibers innervating the glans, and when unmyelinated fibers and additional nerve pathways are factored in, the true number is considerably higher.
To put that in perspective: the clitoris receives about one-third the total number of nerve fibers that the penis does, but because the clitoris is so much smaller, its innervation density per surface area is roughly six times greater. This concentration is what makes the organ capable of intense sensation. It also explains why direct, firm contact with the glans can feel uncomfortable or even painful for many people, while indirect or lighter stimulation often feels better.
How It Responds to Arousal
The clitoris is made of erectile tissue, the same type of spongy, blood-vessel-rich tissue found in the penis. During sexual arousal, blood flow to the clitoral arteries increases, causing the internal tissue to swell and stiffen. The glans becomes more prominent, the internal structures engorge, and the surrounding labia also fill with blood and become more sensitive.
This process is essentially the same mechanism as a penile erection, which makes sense given that the clitoris and penis develop from the same embryonic tissue. In early fetal development, all embryos have an identical structure called the genital tubercle. Depending on hormonal signals, this tissue differentiates into either a penis or a clitoris. Both organs share analogous components: erectile bodies, a surrounding layer of connective tissue, and a glans at the tip. The skin, erectile tissue, and connective structures all trace back to the same cell layers.
Its Role in Orgasm
The clitoris is the primary source of orgasm for most people with vulvas. Unlike the penis, which serves roles in both reproduction and urination, the clitoris has no known function other than sexual pleasure. It plays no direct role in conception, menstruation, or urination.
This has made it a fascinating puzzle for evolutionary biologists. Several theories attempt to explain why it exists. One prominent idea, sometimes called the byproduct hypothesis, argues that the clitoris exists because it shares a developmental blueprint with the penis. Since orgasm is essential for male reproduction, and both organs develop from the same tissue, females retain the capacity for orgasm as an anatomical side effect of that shared design, much like male mammals retain nipples because females need them.
A competing theory proposes that the clitoris originally played a direct role in reproduction. In many mammal species, ovulation is triggered by the physical act of mating, and the clitoral stimulation involved in copulation appears to be part of that trigger. In rabbits, for instance, researchers demonstrated that interfering with the neurochemical pathway involved in orgasm also disrupted ovulation. The idea is that in ancestral mammals, orgasm and ovulation were linked, but as primates evolved spontaneous ovulation (releasing eggs on a hormonal cycle rather than in response to mating), the clitoris became decoupled from reproduction. Supporting this: in species that still rely on mating-triggered ovulation, the clitoral glans tends to sit inside or very near the vaginal canal, while in species with spontaneous ovulation like humans, it sits farther away.
Other theories suggest orgasm evolved to promote pair bonding between partners, to help with mate selection, or to assist with sperm transport through uterine contractions. The sperm transport idea has largely fallen out of favor, as current evidence suggests orgasm plays no meaningful role in moving sperm through the reproductive tract. The pair bonding and mate selection hypotheses remain actively discussed.
Why It Was Overlooked for So Long
Despite being the most nerve-dense structure in the human body, the clitoris was poorly understood by medical science until surprisingly recently. Most anatomy textbooks through the 20th century either omitted the internal structures entirely or depicted them inaccurately. O’Connell’s MRI-based mapping work in the early 2000s was groundbreaking precisely because it demonstrated, with modern imaging, what the full clitoral complex actually looked like in living tissue. Her research showed the consistent relationship between the crura, the bulbs, and the surrounding structures in a way that previous dissection-based studies had failed to capture.
The 2023 nerve fiber count study was similarly notable for being the first of its kind. Researchers pointed out that the commonly cited figure of 8,000 nerve endings, which had circulated for decades, was never based on a direct count in human tissue. The updated figure of over 10,000 myelinated fibers came from actual histological analysis of donated tissue samples, and even that number is an undercount since it excludes unmyelinated fibers and other nerve pathways.
This gap in scientific knowledge has had practical consequences. Surgical procedures in the pelvic region, from episiotomies to gender-affirming surgeries, benefit from precise nerve maps. The more accurately clinicians understand where the clitoral nerves run and how densely packed they are, the better they can preserve sensation during any procedure involving nearby tissue.