External Genitalia and Mammary Glands

Structures lying external to the vagina make up the vulva (external genitalia): the labia majora and labia minora (outer and inner folds of skin), the clitoris, and the hymen, a thin ring of tissue that partially closes the vaginal opening. The hymen is commonly torn at first intercourse but can just as easily be stretched or torn by unrelated activities such as cycling or a fall, so it cannot reliably indicate whether a woman has had intercourse. Two small glands support this region: the Bartholin's (greater vestibular) glands, located either side of the vaginal opening, secrete lubricating mucus and are homologous to the male's bulbourethral glands, while the Skene's glands, on the anterior vaginal wall around the lower urethra, secrete a lubricating fluid and are homologous to the prostate gland. The mammary glands are modified sweat glands present in both sexes but functional only in females; a pair sits in the thoracic region, each containing glandular tissue and varying amounts of fat around a central nipple, which is surrounded by a pigmented areola dotted with small sebaceous (areolar) glands that keep the nipple's skin from cracking. Internally, each gland is organised into 2-25 lobes separated by fat and connective tissue; each lobe is built from lobules containing clusters of milk-secreting alveoli, which drain into mammary tubules, then a wider mammary ampulla, and finally a lactiferous duct that widens under the nipple into a milk-storing lactiferous sinus before opening at the nipple's surface through its ow …