Female internal reproductive anatomy

The urethral sponge is a spongy cushion of tissue, found in the lower genital area of women, that sits against both the pubic bone and vaginal wall, and surrounds the urethra.

The urethral sponge is composed of erectile tissue; during arousal, it becomes swollen with blood, compressing the urethra, helping prevent urination during sexual activity (along with the pubococcygeus muscle). Additionally, the urethral sponge contains the Skene's glands, which with continued stimulation, may produce an ejaculate (usually clear in color) and release it through the urethra during sexual activity or orgasm. Once considered to be urinary incontinence, the ejaculate is not urine, although it is sometimes mixed with urine, and is similar to that produced by the prostate in men. This is said to be a female ejaculation.

The urethral sponge encompasses a large number of pleasurable nerve endings, and can, therefore, be stimulated through the front wall of the vagina. Some women enjoy the rear-entry position of sexual intercourse for this reason, because the penis is often angled slightly downward and can stimulate the front wall of the vagina, and in turn, the urethral sponge.

In fact, the urethral sponge is often synonymously called the G-spot (Gräfenberg spot), although some say that the two are separate. Some women experience intense pleasure from stimulation of the urethral sponge and others find the sensation irritating. The urethral sponge also surrounds the clitoral nerve, and since the two are so closely interconnected, stimulation of the clitoris may stimulate the nerve endings of the urethral sponge.