It's A Mixture
Fluid in the vaginal keeps the tissue moist and healthy, and provides lubrication during sex. The vaginal fluid consists of a mixture of secretions from various mucous, oil and sweat glands. During sexual arousal, vaginal secretions increase due to seepage of fluid through the vaginal wall due to increased blood flow into the tissue. The amount and composition of the vaginal fluid changes throughout the menstrual cycle, and in the time leading up to and after menopause due to hormonal influences.
Cervical Mucous Glands
Glands in the cervix -- the opening of the uterus at the top of the vagina -- contribute a substantial amount of mucus to the vaginal fluid. Mucus is a slippery, water-based substance that contains a variety of proteins and other substances. Several hundred cervical mucous glands secrete fluid on a daily basis, but the amount and consistency changes during the menstrual cycle. Cervical mucus production increases roughly 10-fold at the time of ovulation, compared to other times during the menstrual cycle. However, cervical mucus production does not increase with sexual arousal and is not responsible for the increased amount of vaginal fluid that occurs with sexual excitement.
Bartholin and Skene Glands
Paired mucous glands at the entrance to the vagina -- called Bartholin or greater vestibular glands -- secrete a small amount of mucus when a woman is sexually aroused. This mucus lubricates the vaginal opening to make sexual intercourse more comfortable. In the absence of sexual arousal, the Bartholin glands typically do not contribute to the normal vaginal lubrication.
The paired Skene glands, or the lesser vestibular glands, also secrete mucus. The opening of these glands reside in close proximity to the vaginal entrance near the urethra, the structure through which urine passes from the bladder. The Skene glands normally secrete a small amount of mucus that lubricates the urethral opening. During sexual arousal, mucus production from these glands commonly increases and contributes to the natural vaginal lubrication.
The vaginal tissue itself does not contain mucous, sweat or oil glands. But the vagina does have a rich blood supply, and flow to the area greatly increases during sexual arousal. The resulting engorgement of the blood vessels in the vaginal wall leads to increased pressure, which causes liquid from the blood to seep through the vaginal wall. This fluid, called vaginal transudate, begins to accumulate within the vagina very quickly with sexual excitement. This response, sometimes called vaginal "sweating," is primarily responsible for the increased vaginal wetness women typically experience with sexual arousal.
Oil and Sweat Glands
The inner surface of the labia majora, the outer lips of a woman's genitals, contain a large number of sweat and oil glands. The inner lips, or labia minor, also contain many oil glands. Together, the sweat and oil glands of the labia majora and minora help lubricate the vaginal opening. These glands, however, do not significantly contribute to the increased vaginal lubrication that occurs with sexual arousal.
Reviewed and revised by: Tina M. St. John, M.D.