The objectives of this video are to describe the physiology of female sexual response including arousal and orgasm, to list potential theories for female ejaculation, and to debate the existence of aroginosomes including the G-spot. The female sexual response is extraordinarily complex and relies on the interplay of cortical processing of sexual stimuli and peripheral stimulation of the genitals. Recently, significant attention has been given to female sexual neuroanatomy. The key anatomical structure in female arousal and orgasm is the clitoris. The components of this erectile structure include the glands, the paired corpora or body, and the crura. The structures of the clitoris that are visible externally are the prepuce, glands, and body. The prepuce is also referred to as the clitoral hood and covers the glands and body. The frenulum is just inferior to the glands and is the anterior fusion of the labia minora. The labia majora are fatty folds of skin that are contiguous with the mons pubis cephalad. The glands averages 2 cm long and 3 cm wide and is positioned distal to the body of the clitoris. The body of the clitoris extends anteriorly and superiorly into the fat of the mons pubis and averages 2 cm long and 1-2 cm wide. The body divides posteriorly into the paired crura, which extend posteriorly beyond the ischiopubic rami bilaterally and measure 5-9 cm in length. The crura are covered by the ischiocavernosus muscles. The vestibular bulbs are erectile structures that are closely associated with the clitoris and vagina. They meet in the midline ventral to the urethra and flank the lateral walls of the distal vagina. The vestibular bulbs are covered by the bubble cavernosus muscles. The clitoris is highly innervated by branches of the pudendal nerve. The clitoral branch of the pudendal nerve divides into deep branches to the corpus cavernosum and the dorsal nerve of the clitoris. The skin of the clitoris contains a dense collection of nerve endings and corpuscles. Sensory input is conveyed to the central nervous system via the pudendal, hypogastric, and pelvic splanchnic nerves. The vagus nerve also receives some afferent stimuli from the uterus and cervix, which explains why some patients with lumbosacral spinal cord injuries retain genital sensation. The cell bodies of pudendal sensory neurons reside in the dorsal root ganglia of S2-S4. Their axons travel cephalad in the dorsal columns to the pons. Information is then transmitted to the thalamus and finally to the primary somatosensory cortex. At rest, sympathetic input results in vasoconstriction and decreased blood supply to the genitals. Sexual arousal decreases sympathetic output, which results in vasodilation and increased blood flow to the genitals. Vasocongestion of the genitals begins within three minutes of an arousal stimulus and peaks after about nine minutes. Vasoactive intestinal peptide and nitric oxide are released from nerve endings, leading to increased arterial blood flow and relaxation of vascular smooth muscle. The erectile tissue of the clitoris engorges and the clitoris increases in size 50-300%. The labia increase in size 2-3 fold. The increased blood flow to the vagina results in increased hydrostatic pressure in the local circulation, which leads to formation of the transidative vaginal lubricant. Genital sexual response is not predictive of the subjective experience of female sexual arousal. Vascular changes in the genitals can occur in the absence of subjective arousal. These dynamic 3D MRI images of the vulva demonstrate the changes that occur in the erectile tissue with sexual arousal. The first image is taken during viewing of a neutral video presentation prior to arousal. The second image is taken during arousal while viewing a sexually stimulating video segment and demonstrates a significant increase in size of the right clitoral cruci. Many experts argue that the brain plays the most important role in female sexual function. Images with functional MRI and PET scans have demonstrated activation of numerous cortical and subcortical regions that are involved in visual and emotional processing. The orbital frontal cortex controls appraisal and reward systems. The anterior cingulate area controls emotional initiation and urgency. The anterior temporal areas are part of the paralimbic system. The amygdala is involved in emotional appraisal and assigning positive or negative association with a stimulus. The hypothalamus controls oxytocin release. The caudate nucleus is part of the limbic system and regulates motor control. The insula controls autonomic responses. Interestingly, there is deactivation of areas in the superior and middle temporal gyri that are associated with moral judgment and embarrassment. These areas provide a constant inhibition of sexual arousal that must be released for a successful sexual response. Orgasm has been defined as a variable transient peak sensation of intense pleasure creating an altered state of consciousness, usually accompanied by involuntary rhythmic contractions of the pelvic striated circumvaginal musculature with concomitant uterine and anal contractions and myotonia that resolves the sexually induced vasocongestion, usually with an induction of well-being and contentment. The number of contractions of the pelvic floor muscles correlates with the intensity and duration of the orgasm. During orgasm, peripheral pulse and blood pressure reach twice the resting values. In the absence of continued sexual stimulation, orgasm is followed by the resolution of genital vasocongestion and return of the cardiovascular parameters to the resting state. The term female ejaculation has been applied to a variety of phenomena with different pathophysiologic mechanisms, making research often difficult to interpret. Women may expel a number of different fluids during sexual arousal with volumes ranging from 1 cc to 900 cc. The fluid may originate from the vagina, urinary bladder, Skeen's glands, or from a combination of these sources. The most common fluid is vaginal lubrication. It has been suggested that vaginal fluid may be forcefully expelled from the vagina by contractions of the pelvic floor muscles. This is supported by findings that women with female ejaculation have significantly stronger contractions of the pubococcygeus muscle. Some women expel a small amount of whitish fluid that is believed to originate from the Skeen's glands. This fluid contains prostate-specific antigen, prostatic-specific acid phosphatase, fructose, and glucose, which are characteristic of Skeen's gland secretions. Some experts differentiate this process from squirting or gushing, which refer to the orgasmic transurethral expulsion of a larger quantity of fluid. There is significant debate whether the fluid is urine or diluted chemically altered urine. Studies have found these fluids contain components of Skeen's gland secretions, but other studies have demonstrated that the expelled fluid is actually urine. The current evidence certainly supports that many women experience expulsion of fluid with orgasm, but the source of the fluid is likely variable amongst individuals. The Grafenberg spot, or G-spot, is a controversial topic in anatomy and in female sexual function. In a survey sent to professional women, 84% believe that a highly sensitive area exists in the vagina. In spite of this widespread popular belief, scientific evidence for the existence of a functional G-spot is unclear. Some women describe orgasm achieved from stimulation solely of the G-spot, or a vaginally achieved orgasm, as qualitatively different from orgasm achieved from clitoral stimulation. It is described as being felt deep inside the body and is accompanied by a bearing down sensation. The G-spot is purportedly located on the anterior vaginal wall a few centimeters from the introitus. Histologic examination of this area reveals cavernosal tissue of the clitoral crura, Skeen's glands, muscles, and nerves. Investigators have never located an area on the anterior vaginal wall that is more highly innervated than the surrounding regions. Anatomically, there are no mechanoreceptors in this area that could explain vaginally achieved orgasm. Recent ultrasound studies provide evidence that suggests the G-spot is actually a functional structure composed of the vagina and clitoral body and or crura. Five women who were capable of achieving vaginal orgasms were asked to press their G-spot while transperineal ultrasound was performed. Ultrasound showed that the finger was placed in very close proximity to the clitoral body and that applying pressure with the finger displaced the body and vestibular bulbs. Transperineal ultrasound performed during coitus reveals significant anatomic alterations. The clitoral body and vestibular bulbs are ascending and widened by the penis and the anterior vaginal wall is crushed against the clitoral crura with thrusting. These findings suggest that the G-spot is a functional entity rather than a unique anatomical structure. In conclusion, the female sexual response is a complicated phenomenon that relies on the complex interplay of emotional state, desire, and physical stimuli. Orgasm requires intact pudendal nerve and central nervous system, female ejaculation exists but is a variable occurrence, and the G-spot and vaginal orgasm are likely due to stimulation of the clitoral crura. While an incredible amount of insight has been gained in the past two decades with advances in imaging techniques, many controversies still exist and additional research is needed. For more UN videos visit www.un.org

female sexual response

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