The vagina is a canal from the outside world to a woman’s inner body, with a complex environment that is constantly changing over the course of a woman’s life. The vagina at times inhibits, and other times optimizes, sperm transport during different stages of a woman’s cycle.
It allows sperm to swim inside the woman’s body to meet the egg, while at the same limiting access to sexually transmitted diseases (STDs) that can also be present with semen. It lets blood flow out during our periods. It undergoes chemical changes to help trigger labor and allow for the delivery of a baby. And it helps keep bad bacteria and viruses from invading and establishing disease.
Each woman is protected during all this coming and going by a complex vaginal ecosystem consisting of her own vaginal cells and about 100 million good bacteria that line the vaginal canal. These bacteria come from a woman’s mother during birth and become part of her vaginal ecosystem within 24 hours after she is born.
The good vaginal bacteria (e.g. lactobacillus and related species) produce lactic acid that acidifies the vaginal environment and keeps it at a routinely low pH less than 4.5.
These good bacteria REQUIRE nutrients from a woman’s vaginal cells to survive. These vaginal cells are constantly being exfoliated or shed into the vaginal canal to release the compound glycogen which is broken down by the enzyme amylase (the same type of enzyme as in human saliva). The amylase breaks glycogen down into simple sugars the good bacteria can eat. In exchange for this “free lunch”, the bacteria make lactic acid, which keeps the vaginal ecosystem at a healthy, balanced pH (~4 pH).
How the Vaginal Ecosystem Works
Here’s how the vaginal ecosystem keeps the tightly controlled acidic balance that maintains a healthy vaginal ecosystem:
Fresh vaginal lining cells (called mucosal cells) make Antimicrobial proteins (small natural antibiotics).
Vaginal mucus fibers are secreted by the vaginal lining cells. This mucus lines the vaginal canal, giving the vagina its wet, slippery, appearance, and providing the mucus “armor” coating of the vagina.
Aging vaginal lining cells become flat and thin and are exfoliated (sloughed). These exfoliating vaginal cells produce Glycogen, which is a carbohydrate used by the good bacteria to make lactic acid.
Lactobacillus, “good” bacteria, eat the glycogen made by the vaginal cells for energy, and in turn these bacteria produce Lactic acid molecules in the vaginal canal which keeps the vagina at ~pH 4.
Bad bacteria, yeast, and viruses are stopped from infecting the woman by a combination of:
- being damaged by the low pH lactic acid environment produced by the good bacteria;
- being trapped in the mucus lining of the vaginal canal along with the exfoliating vaginal cells;
- being washed out of the vagina, trapped in the normal, healthy vaginal discharge.
Fresh vaginal cells, mature and turn over daily so it is critical for the mucus “armor” and the good bacteria to be constantly replenished.
Normal vaginal discharge clears the vagina of mucus, exfoliated vaginal cells, and bad bacteria, yeast, and viruses.
Note that douching is bad for a woman’s ecosystem because it washes away too much.
The high volume of fluid washes out not only odor but the mucus armor coating, exfoliating vaginal cells, glycogen for the good bacteria to eat, and the good bacteria themselves.
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