The inside of the vagina is called the vaginal canal (also referred to as the vaginal vault). It is an elastic, muscular tube that connects the external opening (called the introitus) to the cervix at its deepest end. The canal itself is lined with a specialized mucous membrane and has several distinct features worth understanding.
Where the Vagina Begins and Ends
The external genitalia, collectively called the vulva, include the labia, clitoris, and a smooth area known as the vulvar vestibule. The vestibule contains the openings to both the urethra and the vagina. The vaginal canal starts at that opening and extends inward to the cervix, which is the lower portion of the uterus.
At the deepest end of the canal, the space around the cervix forms a ring-shaped recess called the fornix. The fornix has an average depth of about 29 mm and width of about 42 mm, though this varies considerably from person to person. The full length of the vaginal canal from the cervix to the opening averages roughly 63 mm (about 2.5 inches) at rest, with a wide natural range of 41 to 95 mm. These dimensions change substantially during arousal and childbirth because the tissue is highly elastic.
The Lining: Mucosa and Rugae
The inner surface of the vaginal canal is covered by a mucosal layer, a type of tissue similar to what lines the inside of your mouth. This mucosa contains specialized cells that release fluids to keep the vaginal walls moist and protected. Unlike the smooth skin on the outside of your body, the vaginal mucosa has a series of textured ridges called rugae. These folds are what allow the canal to stretch and expand, whether during intercourse, a medical exam, or childbirth, then return to its resting size afterward.
Beneath the mucosa sits a layer of connective tissue called the lamina propria, followed by layers of smooth muscle fiber. Together, these layers give the vaginal wall both flexibility and structural support.
Nerve Distribution Inside the Canal
Sensation is not evenly distributed throughout the vaginal canal. The lower third (closest to the opening) has significantly more nerve fibers than the upper third (closest to the cervix). Research measuring nerve density in the front vaginal wall found nearly twice as many small nerve fibers per square millimeter in the lower third compared to the upper third. This is why the entrance and lower canal are far more sensitive to touch, while the deeper portions have comparatively little sensation.
How the Vaginal Canal Cleans Itself
The inside of the vaginal canal maintains its own environment without any need for internal washing. A community of beneficial bacteria, predominantly Lactobacillus species, ferments a sugar called glycogen (naturally shed by vaginal cells) into lactic acid. This keeps the pH between 3.8 and 5.0, which is moderately acidic. That acidity, along with antimicrobial compounds the bacteria produce, prevents harmful organisms from taking hold.
Vaginal discharge is a visible part of this system. It consists of fluid produced by the cervix and vaginal walls, shed epithelial cells from the mucosa, and bacteria. This discharge carries debris out of the canal continuously. The vaginal lining also turns over rapidly, shedding its outermost cells on a regular cycle, which physically removes bacteria clinging to the surface. Cells in the lining produce their own antimicrobial substances, adding another layer of defense. This self-cleaning process typically begins a year or two before puberty and continues until after menopause.
Quick Reference: Key Anatomical Terms
- Vaginal canal (vaginal vault): the full internal tube from the opening to the cervix
- Introitus: the external opening of the vagina
- Fornix: the ring-shaped recess surrounding the cervix at the deepest point of the canal
- Rugae: the ridged folds on the inner vaginal walls that allow stretching
- Vaginal mucosa: the moist mucosal lining covering the inside surface
- Lamina propria: the connective tissue layer beneath the mucosa, rich in blood vessels and nerves
- Vulvar vestibule: the smooth area just outside the vaginal opening, part of the external anatomy (vulva), not the internal canal