Fig.1. External genitals in female.



Massage, irritation, or other types of excitation of the perinea region, of the sexual organs and of the urinary tract, generate sexual sensations.

These sensations are taken to the spinal cord through the pudendal nerve and sacral plexus (fig.2). Besides, the local reflexes responsible at least for part of the feminine orgasm are integrated in the medulla sacra lumbar.

Fig.2. Innervation of female reproductive organs showing autonomic nerves containing sympathetic and parasympathetic efferent and afferent fibers In Blue: Parasympathetic fibers. In Red: Sympathetic fibers.

The clitoris is the main sex organ involved with the local excitation, receives, responds to, and transmitts neural messages of the sexual stimulation. It contains both afferent (those that go to the spinal cord) and efferent (those that come from the spinal cord) neural pathways.

Near the vestibule (the entrance of the vagina) (fig.3), and extending up to the clitoris, there exists an erectible tissue almost identical to the erectible tissue of the penis. This tissue is controlled by the parasympathetic nerves that pass through the erector nerves of the sacral plexus to the external genitals.
it is assumed that androgens determines the reponsiveness to erotic stimuli, that is, they cause growth of the clitoris (2). In the absence of androgenic stimulation, arousability would be low, and stimuli would not act to increase arousal.

Fig.3. Female external genitalia

The sympathetic impulses continue to the Bartholin's glands (fig. 2) bilaterally localized below the labium minus causing the secretion of mucus immediately inside of the vestibulum. This mucus, together with great quantity of mucus produced by the vaginal mucosity is responsible for the adequate lubrication during the sexual intercourse. Local sexual excitation goes to spinal cord through pudendal nerve and sacral plexus (fig.2). After penetrating the spinal cord, the impulses are transmitted to the brain. This lubrication, on the other hand, is necessary to promote a satisfactory and enjoyable sensation of massage during the intercourse, instead of a sensation of irritation that can be produced by a dry vagina.

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Author: Dr. Silvia Helena Cardoso, PhD. Psychobiologist, master and doctor in Sciences by the University of São Paulo and post doctoral fellowship by the University of California, Los Angeles. Invited Professor and Associate Researcher of the Center for Biomedical Informatics, State University of Campinas (Unicamp), Brazil.