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.