Male and female external genitalia, arising from identical embryologic anlage, differentiate depending on the presence or absence of testosterone. Lack of the SRY gene (typically found on the Y chromosome) leads to development of ovaries, with subsequent maturation of female sex organs. The labia majora is a cognate of the scrotum and the clitoris and penis are similarly derived. Ambiguous genitalia occur when development and maturation occurs with a mixed genetic substrate or hormonal environment.
The female reproductive system consists of the ovaries on their suspensory ligaments, the Fallopian tubes, the uterine corpus and cervix, the vagina with its muscular wall, the vaginal and introital glands of Cowper and Bartholin, the labia minora and majora, and the clitoris with its covering prepuce.
The ovary cyclically matures one ovum within a follicle under the stimulation of follicle-stimulating hormone (FSH) from the pituitary. The developing follicle produces estrogen, which causes proliferation of the endometrium. When the serum estrogen level reaches a threshold, a luteinizing hormone (LH) surge is triggered from the pituitary, effecting ovulation and formation of the corpus luteum that secretes increased levels of progesterone, inducing transformation of the endometrium from its proliferative to its secretory phase. The released ovum is captured by the fimbriated end of the Fallopian tube down which it travels to the uterine corpus. If fertilized in the tube or uterine cavity, the ovum may implant into the receptive endometrium establishing a pregnancy. If not, implantation does not occur and the corpus luteum involutes. With the cessation of estrogen and progesterone production, the endometrium is sloughed as menstrual bleeding, FSH rises again to stimulate development of another follicle initiating another reproductive cycle. Implantation of a fertilized ovum leads to the development of the placenta, which secretes human chorionic gonadotropin, suppressing pituitary FSH and LH, leading to cessation of ovulation and menstruation.
The symphysis pubis is surmounted anteriorly by a fat pad, the mons pubis (Fig. 11–1). At puberty, the eminence becomes covered with hair that extends onto the skin of the abdomen to form a transverse borderline, the base of an inverted triangle called the female escutcheon. This hair distribution contrasts with that of the male escutcheon, which describes an upright triangle with the apex near the umbilicus.
Anatomy of the Uterus and Adnexa. A. Sagittal section of the female pelvis: Note the angle of the vagina with the vertical axis of the body, and the axis of the uterus perpendicular to the vaginal axis. The lips of the cervix uteri are shown to be in the same plane as the anterior vaginal wall, which is shorter than the posterior wall. The rectovaginal pouch (cul-de-sac of Douglas) lies anterior to the rectal wall; hence, it can be palpated during the rectal examination. The uterine fundus in the usual position is inaccessible to the rectal examining finger, but very close to palpation from the lower abdomen.B. View of the pelvis from above and in front:Note how the round ligament curves anteriorly and the uterine tubes curve posteriorly.C. Posterior view of the uterus and broad Ligaments, Spread Out:Note the suspension of the ovary near the fimbriated end of the uterine tube. The uterine tube forms the upper border of the broad ligament.
The vulva or pudendum is the female external genitalia (Fig. 11–2B). The labia majora are elevated ridges extending inferiorly and posteriorly from the mons pubis nearly to the anus. They contain fat, blood vessels, nerves, and tissue that resemble the dartos tunic in the scrotum. Enclosed within the labia majora are two smaller skin folds, the labia minora, extending from the clitoris to unite in front of the anus by a transverse fold, the fourchette. The clitoris is the erectile homologue of the penis, composed of two small corpora cavernosa and surrounded superiorly by the prepuce and inferiorly by folds of the labia minora, the frenulum. The cleft posterior to the clitoris, between the two labia minora, is called the vestibule. It is pierced by the urethral meatus, approximately 2.5 cm posterior to the clitoris, and the vaginal orifice, immediately posterior to the meatus. The vaginal opening is a median slit, varying inversely with the size of the hymen. The hymen is a thin membrane covering part of the vaginal orifice. Commonly a perforate ring, widest posteriorly, the hymen may be cribriform, fringed, or even imperforate. After rupture, the hymenal remnants heal as irregular folds of mucosa. Two paired glands open onto the vestibular surface: just inferior to the urethra are the openings of the paraurethral (Skene) glands, and at the posterior edge of the vaginal orifice are found the openings of the greater vestibular (Bartholin) glands.
Examination of the Vulva. A. Draping for pelvic examination:The patient assumes the lithotomy position with feet in stirrups projecting from the end of the examining table. A sheet is spread over the patient so the two lower corners are wrapped about the thighs and legs. The middle of the lower edge of the sheet is slackly draped over the lower abdomen.B. Topographic anatomy of the vulva:The recessed vestibule contains a relatively small vaginal orifice, surrounded by one of the usual patterns of unruptured hymen. Bordering the vestibule are the two projecting folds of often deeply pigmented skin, the labia minora. Anteriorly, accessory folds of the labia form the prepuce that encloses the clitoris. Lateral to the labia minora are two parallel ridges of skin and fat that form the labium majus on either side of the labia minora.
The vagina, uterus, and adnexa