Vagina The vagina is the organ that receives the male sperm during intercourse. It also forms the lower portion of the birth canal, stretching widely during delivery. In addition, it serves as an excretory duct for uterine secretions and menstrual flow. The vagina is a fibromuscular tube capable of great distention. The canal is approximately 9 cm long and extends from the uterus to the outside. The vaginal orifice is partially closed by a thin membrane of tissue called the hymen. The wall of the vagina consists of three layers. The inner mucosal layer does not have mucous glands; the mucous found in the vagina comes from the glands of the cervix. The middle muscular layer consists mainly of smooth muscles fibers. At the lower end of the vagina is a thin band of smooth muscle that helps close the vaginal opening. The outer fibrous layer consists of dense fibrous connective tissue interlaced with elastic fibers. These fibers attach the vagina to the surrounding organs. EXTERNAL ACCESSORY ORGANS Many of the external accessory organs of the female reproductive system are referred to collectively as the vulva. The vulva includes the labia majora, the labia minora, the clitoris, and the vestibular glands (fig. 1-63). The mammary glands are also considered an accessory organ of the female reproductive system. Labia Majora The function of the labia majora is to enclose and protect the other external reproductive organs. The labia majora are composed of two round folds of fat tissue and a thin layer of smooth muscle, covered by skin. On the outer portion of the labia majora, the skin has numerous hairs, sweat glands, and sebaceous glands. The inner portion of skin is thin and hairless. The labia majora extend from the mons pubis anteriorly to the perineum (the region between the vaginal orifice and the anus). The mons pubis is the pad of fatty tissue beneath the skin, which overlies the symphysis pubis. Labia Minora Within the labia majora folds are two smaller folds, called the labia minora. The labia minora extend from the clitoris to either side of the vaginal orifice. Clitoris The clitoris is a small projectile at the anterior end of the vulva between the labia minora. It is richly endowed with sensory nerves that are associated with the feeling of pleasure during sexual stimulation. Vestibule The vestibule is the area enclosed by the labia minora that includes that vaginal and urethral openings. The vestibule contains a pair of vestibular glands, more commonly known as the Bartholin's glands. The Bartholin's glands lay on each side of the vaginal opening. The ducts of these glands secrete fluid that moistens and lubricates the vestibule. Mammary Glands The mammary glands, or breasts, are accessory organs of the female reproductive system. They develop during puberty under the influence of the hormones estrogen and progesterone. The breasts are responsible for the secretion of milk (lactation) for the nourishment of newborn infants. Structurally, the breasts resemble sweat glands. At the center is a nipple containing 15 to 20 depressions into which ducts from the lobes of the gland empty. During pregnancy, placental estrogen and progesterone stimulate further development of the mammary glands 1-62 MONS PUBIS LABIA MAJORA LABIA MINORA HYMEN ANUS CLITORIS URETHRAL ORIFICE VAGINAL ORIFICE OPENING OF VESTIBULAR GLAND HM3f0163 Figure 1-63.—External reproductive organs.