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Monday, July 11, 2011

Female Sexual Function and Dysfunction - Knol

Source Knol: Female Sexual Function and Dysfunction

by Tom F. Lue, Professor and Vice Chair of Urology University of California, San Francisco
Alan Shindel, Assistant Professor of Urology, University of California, Davis, University of California Davis Medical Center
Irwin Goldstein, Director of Sexual Medicine, Alvarado Hospital; Clincial Professor of Surgery, UCSD, San Diego, California

Introduction

In 1893, the physician and sexual medicine specialist Edward Martin stated, “In the case of a woman, performance of the sexual act, at least insofar as her partner is concerned, requires only the presence of a sufficiently long and patulous (open) mucous canal.”[1] While this statement may seem shockingly misogynistic (hating or dismissive of women), when it was written it was fairly progressive to openly address women’s sexuality. Although our understanding of women’s sexual function and dysfunction has not progressed as rapidly as our understanding of men’s sexuality has, we have certainly made progress since Martin’s day.

Female Sexual Function
What are the phases of sexual response in women?

The famed sex researchers William Masters and Virginia Johnson derived a basic scheme for sexual response in men and women consisting of four distinct phases called excitement, plateau, orgasm, and resolution.[2] In the vast majority of men studied by Masters and Johnson these steps occurred in a fairly predictable pattern. In contrast, these researchers found much more variation among women with respect to sexual experience. In some women the sequence of events was similar to what was observed in men (blue line in graphic below). In other women a discrete orgasm phase did not occur (violet line in graphic below) and in some women there were multiple orgasms during a single sexual encounter (yellow line in graphic below). Helen Singer Kaplan, another prominent sex researcher, later elaborated on the Masters and Johnson schema by incorporating the concept of desire, defined as an interest in sexual activity that precedes actual sexual arousal.[3]

The paradigm created by Masters, Johnson, and Kaplan has been accepted for many years as representative of sexual response in both men and women. Recently, a leading expert in women’s sexual health (Rosemary Basson) has advocated a new model of female sexual function that stresses the interdependence of relationship factors and sexual function in women. In this new model, sexuality and sexual function in women follow a circular path in which emotional cues and relationship issues play a fundamental role and intrinsic sexual desire plays a much smaller role.[4]

No one model can adequately encompass the sexual experience for all individuals. In a recent study of 129 women, about 2/3 of respondents endorsed the Masters & Johnson model as most representative of their sexual response, while approximately 1/3 selected the Basson model. Interestingly, women who endorsed the Basson model were more likely to have sexual health concerns, particularly low sexual desire.[5]

What physical changes occur during the sexual response cycle in women?

During sexual arousal in women, numerous changes occur throughout the body. For the purposes of this review, we will focus on genital changes only. The attached diagrams demonstrate the anatomy of the female pelvis with a focus on the genital organs.

Vaginal lubrication

Prior to the 1960s, it was thought that the vaginal lubrication produced during sexual arousal was derived from glandular tissue. However, in a series of elegant experiments Masters and Johnson demonstrated that there were no discrete glands within the vagina and therefore vaginal lubrication could not be derived from glands.[2] It was subsequently discovered that vaginal lubrication is caused by the production of a transudate (a watery fluid with very low protein content) from the blood vessels supplying the vagina. Normally, the walls of blood vessels do not permit fluid to leak through. However, during sexual excitement, increased blood flow to the pelvic region causes pressure to build up in the small blood vessels around the vagina. This process is driven by nerves from the sacral portion of the spinal cord, which is part of the parasympathetic nervous system. This increased pressure forces fluid out of the blood vessels and into the vaginal canal, thus producing a slippery lubricant fluid. This fluid is the lubrication that a woman feels when she gets wet from sexual arousal.[6]

The clitoris is composed of inner-tube like cylinders of spongy tissue called corpora cavernosa. The internal portion (crura) of the clitoris attaches to the pelvic bones. During sexual excitement, blood flow to the corpora cavernosa increases, causing them to swell. Because the veins that drain blood from the clitoris are located to the side of the corpora cavernosa, compression from the swelling corpora will tend to obstruct these veins, causing blood to become trapped inside the clitoris. The overall process leads to engorgement (enlargement) and increased sensitivity of the clitoris.[7]

What about female ejaculation and the G spot?

During sexual climax, some women experience a spurting of fluid from the urethra; this is commonly referred to as female ejaculation. This is an atypical but not abnormal occurrence and should not be interpreted as a problem.

The G spot (or Grafenberg Spot, for the physician who first described it) is an anatomical area that can be a source of great pleasure during sexual stimulation for some women. It is most commonly located on the front wall of the vagina near the base of the bladder although the exact location may vary. The G Spot has been a source of great controversy in the medical community as some investigators contend that there is not enough evidence to prove its existence.[8] Other experts and many women very strongly maintain that the G spot does exist and can play an important role in sexual pleasure.[9]

The existence and importance of the “G spot” for a particular woman’s enjoyment of sex varies from woman to woman, like most aspects of sexuality. Interestingly, women who ejaculate at climax report sensitivity in the expected location of the G spot more frequently than women who do not ejaculate. [9] The G-spot has often been referred to as a “female prostate,” and recent evidence has supported the notion that the “G-spot” may indeed be a gland that surrounds the urethra and produces the fluid ejaculated at orgasm. The physical characteristics of female ejaculate have been not been well studied but there is good evidence that it is similar in some respects to semen, which is ejaculated by men at climax.[10] Further research is needed before definitive statements about the G spot and female ejaculation can be made. For the time being, G spot sensitivity and ejaculation can be considered normal variants of female sexual response.

It is a fairly long article and there is a lot of content on Female Sexual Disorders. There are images explaining anatomy of various organs. Visit source knol for more detailed content.

Source Knol: Female Sexual Function and Dysfunction

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