Chapter 11

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.

###### Fig. 11–1.

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 ...

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