During vaginal intercourse, the penis enters the vaginal opening, which is located between the urethral opening (where urine exits) and the anus. Understanding the basic layout of this anatomy helps clarify exactly where penetration occurs and how the body accommodates it.
The Three Openings
The area between a woman’s legs, called the vulva, contains two visible openings, with a third (the anus) located further back. From front to back, the order is: the urethral opening, the vaginal opening, and the anus. All three are distinct, and each serves a different function.
The urethral opening is small and sits just below the clitoris. Its only job is to release urine from the bladder. It is not involved in intercourse, and a penis cannot enter it. The vaginal opening sits just below and behind the urethral opening, surrounded by the inner lips (labia minora). This is the opening the penis enters during vaginal sex. Further back, past the perineum (the small stretch of skin between the vaginal opening and the anus), is the anal opening.
What the Vaginal Canal Looks Like Inside
The vagina is a flexible, muscular canal that extends inward from the vaginal opening. When a person is not aroused, the canal is roughly two to four inches long, and its walls rest against each other, so it isn’t a gaping hole. During arousal, the vaginal walls relax, the canal lengthens to roughly four to eight inches, and the body produces natural lubrication. These changes make penetration more comfortable and possible.
At the deepest end of the vaginal canal sits the cervix, a firm, rounded barrier that marks the entrance to the uterus. The cervix is typically three to six inches inside the vaginal canal. It prevents anything (a penis, a tampon, fingers) from passing into the uterus. During pregnancy, the cervix seals tightly shut and forms a mucus plug to protect the developing fetus.
How to Locate the Vaginal Opening
If you or a partner are having trouble finding the vaginal opening, it helps to know what to feel for. The outer lips (labia majora) are the first thing you’ll encounter. Parting them reveals the inner lips (labia minora), which frame both the urethral opening and the vaginal opening. The vaginal opening is the larger of the two and sits lower, closer to the anus. It may feel like a soft indentation or slight opening in the tissue.
Arousal makes the vaginal opening easier to identify because increased blood flow causes the labia and clitoris to swell slightly, and the vaginal opening becomes more relaxed and lubricated. Taking time for foreplay isn’t just about comfort. It physically changes the anatomy in ways that make penetration smoother and easier to navigate.
Anal Penetration Is a Separate Choice
Some people also engage in anal sex, where the penis enters the anus instead of the vagina. This is a different act from vaginal intercourse and involves different anatomy. The anus leads into the anal canal and then the rectum. Unlike the vagina, the anus does not self-lubricate, so external lubrication is necessary to reduce the risk of tissue tears. The anal canal and rectum are lined with nerve endings, which is why some people find anal stimulation pleasurable. In men, the rectum sits next to the prostate gland, which adds another source of sensation during anal penetration.
Anal sex is entirely elective and requires clear communication between partners. Because the tissue in the anal canal is more delicate than vaginal tissue, going slowly and using plenty of lubrication matters significantly.
Why Arousal Matters for Comfortable Penetration
The vagina’s ability to stretch and accommodate a penis depends heavily on arousal. Without it, the vaginal canal is shorter, tighter, and dry, which can make penetration painful or difficult. With adequate arousal, the vaginal walls relax, the canal elongates, and natural lubrication reduces friction. This is a physiological process, not something that can be rushed. If penetration feels difficult or painful, it usually means more time is needed for arousal, or that additional water-based lubricant can help.
After sex, the vulva may look temporarily different. Swelling of the labia and clitoris from increased blood flow and friction is normal and subsides on its own. The vagina returns to its resting size and shape afterward. It does not permanently change from intercourse.