The clitoris is the primary organ for sexual pleasure in people with vulvas. Its sole known function is to provide sensory stimulation during sexual activity, making it the only organ in the human body dedicated entirely to pleasure. But there’s far more to it than the small, visible nub most people picture. The majority of the clitoris is internal, and its role during arousal involves a complex chain of events that affect surrounding tissue, blood flow, and nerve signaling.
More Than What You Can See
The visible part of the clitoris, called the glans, is a small rounded structure at the top of the vulva, partially covered by a fold of skin called the clitoral hood. On average, the glans is roughly 6 to 7 millimeters long and about 5 millimeters wide, though there’s a wide range of normal variation from person to person.
That external tip, however, is just a fraction of the full organ. Inside the body, the clitoris is shaped like an upside-down wishbone. The top of that wishbone, called the body, extends behind the glans and then branches into two legs known as the crura. These crura are actually the longest parts of the clitoris, and they flank the vaginal canal and urethra on either side. Sitting between the crura and the vaginal wall are two structures called the vestibular bulbs, which play a key role during arousal.
Altogether, the internal clitoris forms something closer to a pyramid-shaped structure with a broad attachment to the pubic bone. Landmark anatomical work by urologist Helen O’Connell, using MRI imaging and cadaver dissections, revealed that the clitoris is far larger and more complex than medical textbooks had traditionally shown. Her research demonstrated that the organ has a consistent, close relationship to both the urethra and the vagina, which helps explain why stimulation of nearby areas can feel pleasurable.
What Happens During Arousal
When sexual stimulation begins, the clitoris undergoes changes similar to what happens in a penis during an erection. The erectile tissue inside the clitoral body and crura relaxes, allowing blood to rush in. This causes the tissue to swell, the internal pressure to rise, and the glans to become more prominent and exposed. The vestibular bulbs engorge with blood too, and can double in size during full arousal. This swelling tightens the tissue around the vaginal opening and increases sensitivity across the surrounding area.
The chemical process behind this is the same one that drives erections in penises: nerve endings and blood vessel walls release a signaling molecule that relaxes smooth muscle in the arteries feeding the clitoris, flooding the tissue with blood. This isn’t a coincidence. During fetal development, the clitoris and penis develop from the same structure, called the genital tubercle. The glans of the clitoris corresponds to the glans of the penis, and the internal erectile bodies are structural equivalents as well. The key difference is that the clitoris has no role in urination or reproduction. It exists purely for sensation.
An Exceptionally Dense Nerve Supply
The clitoris is one of the most nerve-rich structures in the human body. Histological studies have found that its innervation density is 6 to 15 times greater than that of the penis, and research in mice has measured the clitoral glans at 16 times the density of touch-sensing nerve cells compared to the penile glans. The nerves serving the clitoris are paired branches of a larger nerve bundle that runs along the pelvic sidewall, and they’re substantial enough to measure about 2 millimeters in diameter even in infancy.
This concentration of nerve endings is why direct or indirect clitoral stimulation is so central to orgasm. In a study of heterosexual women who had experienced orgasm during partnered sex, 93.4% said their most reliable route to orgasm involved clitoral stimulation, whether alone or combined with vaginal penetration. Only 6.6% identified vaginal penetration alone as their most reliable method. During masturbation, the numbers were even more stark: 99% of women relied on clitoral stimulation, and just 1% used vaginal penetration alone.
Its Role in Orgasm
Orgasm triggered through clitoral stimulation involves rhythmic contractions of the pelvic floor muscles and a surge of hormones, including prolactin and oxytocin. These hormones contribute to the feelings of release and satisfaction that follow orgasm. Interestingly, this hormonal response may hold clues to the clitoris’s evolutionary origins.
Researchers at Yale have proposed that female orgasm originally served a direct reproductive purpose. In many other mammals, the same neuroendocrine reflex (the hormonal surge that accompanies orgasm) triggers ovulation. In these species, ovulation doesn’t happen on a cycle; it’s induced by mating. The theory is that as human ancestors evolved to ovulate spontaneously on a monthly cycle, this reflex was no longer needed for reproduction. Freed from that role, it persisted as the sensation we now experience as orgasm. So while the clitoris doesn’t play a direct role in human reproduction today, it likely descends from a system that once did.
Why “Vaginal” Stimulation Often Involves the Clitoris
Because the internal portions of the clitoris wrap around the vaginal canal, the line between “clitoral” and “vaginal” stimulation is blurrier than most people assume. Pressure on the front wall of the vagina, the area sometimes called the G-spot, applies indirect pressure to the internal clitoral structures and the surrounding nerve-dense tissue. O’Connell’s MRI-based research confirmed that the clitoris, urethra, and vagina form an interconnected midline core. Stimulation of one often affects the others.
This is likely why the vast majority of women find combined stimulation (both vaginal and clitoral) more reliable for orgasm than either alone. It’s not that vaginal and clitoral pleasure are separate systems. They’re different access points to the same underlying network of erectile tissue and nerves.