During vaginal sex, the penis goes into the vaginal opening. This is one of three separate openings in the vulva area, and it’s specifically designed to accommodate penetration. Understanding which opening is which can feel confusing if no one has ever clearly explained the anatomy, so here’s a straightforward breakdown.
Three Openings and Where They Are
From front to back, there are three openings in the female genital and pelvic area:
- The urethral opening is the small hole where urine comes out. It sits near the top, just below the clitoris. In females, the urethra is only about 1.5 inches long, and the opening is far too small for a penis to enter. This is not the right opening.
- The vaginal opening is located just below the urethral opening. This is where a penis goes during vaginal intercourse. It’s also where menstrual blood exits the body and where tampons are inserted.
- The anus is the opening farthest back, closer to the tailbone. Some people engage in anal sex, which involves penetration here, but this is a different act from vaginal sex and requires different precautions.
All three openings are relatively close together, which is why the anatomy can be confusing, especially in the dark or without much experience. The vaginal opening is the middle one, surrounded by the inner folds of skin called the labia minora.
How the Vagina Accommodates Penetration
The vaginal canal is naturally elastic. When a person is not aroused, it’s about two to four inches deep. During arousal, it elongates to between four and eight inches. Two things happen to make this possible: the cervix (the barrier at the top of the canal) lifts upward, creating more room, and the tissue lining the vaginal walls expands like an accordion as blood flow increases to the area.
Small glands on each side of the vaginal opening secrete fluid that lubricates the vagina during arousal. This natural lubrication reduces friction and makes penetration more comfortable. When arousal is insufficient or lubrication is limited, using a store-bought lubricant helps prevent discomfort or irritation.
The Hymen and First-Time Penetration
The hymen is a thin ring of tissue around the vaginal opening. In most people, it doesn’t fully cover the opening. It naturally has a gap large enough for menstrual blood and tampons to pass through. The hymen stretches or wears down gradually over time from everyday activities, tampon use, or sexual activity.
In rare cases, the hymen may be unusually thick, have only a very small perforation, or have a band of tissue across the middle (called a septate hymen). These variations can make first-time penetration difficult or uncomfortable and sometimes need minor medical treatment. But for most people, the hymen does not block the vaginal opening.
What About Anal Sex?
The anus is a separate opening that some people use for sex. Unlike the vagina, the anal canal does not produce significant lubrication on its own. The mucous lining inside secretes a small amount of mucus meant to help with bowel movements, but it’s not enough for comfortable penetration. External lubricant is essential to prevent tearing or injury to the delicate anal tissue.
The anus also has two ring-shaped muscles (sphincters) that keep it tightly closed. One relaxes automatically, and the other is under conscious control. Relaxation and gradual entry matter more here than with vaginal penetration because forcing past tense muscles can cause pain or small tears.
STI Risk Differs by Type of Sex
The type of penetration affects the risk of sexually transmitted infections. CDC data on HIV transmission illustrates this clearly: the risk of HIV transmission per act of receptive anal sex (without protection) is roughly 1 in 72, while receptive vaginal sex carries a risk of about 1 in 1,250. That makes receptive anal sex roughly 17 times riskier for HIV per encounter. The anal lining is thinner and more prone to small tears, which creates easier entry points for infections.
Condoms and other barrier methods significantly reduce these risks for both vaginal and anal sex.
Finding the Right Opening
If you’re having trouble locating the vaginal opening during sex, that’s completely normal, especially early on. A few practical tips: the vaginal opening is lower than many people expect, sitting below the urethral opening and above the anus. Having your partner guide you with their hand can help. Good lighting or exploring with fingers first makes the anatomy easier to identify. Using lubricant on the tip of the penis also makes entry smoother if you’re not perfectly aligned on the first try.
Communication helps more than anything. Asking your partner to help position things isn’t awkward; it’s practical, and most partners appreciate it.