From Encyclopedia of Sex and Sexuality
The labia majora are composed of two rounded mounds of tissue. They originate in the mons pubis and terminate in the perineum, forming the lateral boundaries of the vulva. After puberty, hair grows on the skin of the labia majora; on their inner sides they have many sweat glands. The male and female genitalia develop from the same embryonic origin, and the labia majora are homologous to the male scrotum.
The labia minora are smaller folds of hairless skin usually hidden between the labia majora. They surround the vestibule—the entry to the opening—of the vagina. These folds are smooth and pigmented, and at their upper ends meet to form around the clitoris. The labia minora are equivalent to the skin of the penis in males.
The clitoris is the principal organ of female sexual pleasure. It lies beneath the mons pubis at the top of the vaginal vestibule. Similar to a small button or pea in size and shape, it is capable of some enlargement, caused by increased blood supply during sexual excitement or when touched. It is rich with nerve endings and is a very erogenous organ. It is comparable to the penis, developing from the same tissue in the embryo. The urethra is a membranous structure for the passage of urine. It is approximately two inches long. Its opening lies below the clitoris.
The vestibule is the area bordered by the labia minora laterally, the clitoris above, and the fusion of labia minora below. It is the entry into the vaginal canal. In girls and young women prior to sexual intercourse and pregnancy, the junction between the vagina and the vestibule is covered by a membrane called the hymen. There are usually one or several orifices in the hymen that allow menstrual blood or other secretions to flow out of the vagina, but in some cases the hymen is imperforated (has no openings) and menstrual blood accumulates in the vagina. A simple procedure called hymenectomy can resolve the problem. After sexual intercourse the hymen tears and only fragments of it remain on the edges of the vaginal opening. In some cases bleeding may occur when the hymen is torn.
The Batholin glands lie at the lateral aspect of the vulva, beneath the labia. These glands’ secretions, which lubricate the vulva and vagina, especially during sexual activity, appear through two duct openings that lie on the low lateral position of the vaginal opening. After about age thirty the glands undergo involution and shrink. The Batholin glands tend to form cysts and abscesses. While cysts may not be bothersome, abscesses should be surgically treated.