Physiology of Vaginal Lubrication

Vaginal lubrication consists of ultrafiltered blood, and thus is

Reliant on healthy blood flow.

• The vagina contains no glands.

• Blood pressure pushes fluid from the capillaries throughintercellular gap junctions between vaginal epithelial cells.5The resultant vaginal transudate is mainly composed ofwater and very small proteins that combine at the vaginalsurface with dead epithelial cells.

• Sufficient pelvic blood flow depends on the bioavailability of nitric oxide (NO). Gaseous NO is producedin capillary endothelia in response to shear stress or inresponse to sexual arousal through parasympatheticnitrergic nerves.6 Once produced, NO induces vasodilation through a cyclic guanosine monophosphate cascade,which diminishes as phosphodiesterase enzymes breakdown the cascade.

• Therefore, vaginal lubrication production depends on thesynthesis, enzymatic facilitation, and bioavailability of NO(Box 56-1). The enzymatic function of NO synthase isenhanced by steroid hormones, most notably estrogen ina rapid-action nongenomic effect.7

• The presence of NO is not sufficient for its effect. Manybiologic feedback mechanisms suppress the productionof NO, because high production of NO in an inflammatory environment can lead to irreversible free radicalproduction.8 Metabolic conditions of low inflammationsupport the bioavailability of NO in facilitating vaginallubrication.

The vagina's lubrication comes not from glands but from a transudative fluid expressed through vaginalepithelial cells. Transudation requires adequateperfusion and nitric oxide.

TABLE 56-1. Risk Factors for Vaginal Dryness

Reduced estrogen Availability

Postpartum status, breast-feeding Menopausal transitionPremature ovarian failureOophorectomyPelvic radiotherapy

Other Medical Conditions

Untreated hypertension Diabetes (types 1 and 2), metabolicsyndromePituitary disorders

Neuropathies, especially autonomic neuropathy

Dermatoses (psoriasis, lichen sclerosis, Sjogren syndrome)

Prescription

Medications

Antihistamines and decongestants Antidepressants (SSRIs, atypical, TCAs)Antiestrogen therapy forchemoprophylaxis

Antiestrogen therapy for endometriosis or fibroidsChemotherapyDiuretics

Progesterone predominant oral contraceptives

Unwise Behaviors

Dehydration, including alcohol use Use of douches, extremely hotbaths, or strong detergents anddehydrating soapsUse of highly absorptive tamponsUse of male condoms with insufficientexternal lubricant

Lack of sufficient arousal before vaginal penetrationSmoking

SSRIs, selective serotonin antidepressants.

Reuptake inhibitors; TCAs, tricyclic


BOX 56-1. Manipulation of Nitric Oxide Function

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