, the vagina provides a passageway for delivery of
an infant and for menstrual ﬂow. Because it receives the penis
(and semen) during sexual intercourse, it is the
female organ of
Te distensible wall of the vagina consists of three coats: an
, a smooth muscle
marked by transverse ridges or rugae, which
stimulate the penis during intercourse. Te mucosa is a stratiﬁed
squamous epithelium adapted to stand up to friction.
in the mucosa act as antigen-presenting cells and are thought
to provide the route of HIV transmission from an infected male
to the female during sexual intercourse. (Chapter 21 describes
AIDS, the immune deﬁciency disease caused by the HIV virus.)
Te vaginal mucosa has no glands. Instead, it is lubricated
by the cervical mucous glands and the mucosal transudate
that “weeps” from the vaginal walls. Its epithelial cells release
large amounts of glycogen, which resident bacteria metabolize
anaerobically to lactic acid. Consequently, the pH of a woman’s
vagina is normally quite
. Tis acidity helps keep the va-
gina healthy and free of infection, but it is also hostile to sperm.
Although vaginal ﬂuid of adult females is acidic, it tends to be
alkaline in adolescents, predisposing sexually active teenagers
to sexually transmitted infections.
In virgins (those who have never participated in sexual
intercourse), the mucosa near the distal
an incomplete partition called the
. Te hymen is very vascular and may bleed when
it stretches or ruptures during the ﬁrst coitus (sexual inter-
course). However, its durability varies. In some females, it
is ruptured by sports, inserting tampons, or pelvic examina-
tions. Occasionally, it is so tough that it must be breached
surgically if intercourse is to occur.
Te upper end of the vaginal canal loosely surrounds the
cervix of the uterus, producing a vaginal recess called the
. Te posterior part of this recess, the
, is much deeper than the
Figures 27.12 and 27.14). Generally, the lumen of the vagina is
quite small and, except where the cervix holds it open, its pos-
terior and anterior walls touch each other. Te vagina stretches
considerably during copulation and childbirth, but its lateral
distension is limited by the ischial spines and the sacrospinous
Te uterus tilts away from the vagina. For this reason, attempts
by untrained persons to induce an abortion by entering the
uterus with a surgical instrument may puncture the posterior
wall of the vagina. Tis causes hemorrhage and—if the instru-
ment is unsterile—peritonitis.
Check Your Understanding
Why are women more at risk for PID than men?
Oocytes are ovulated into the peritoneal cavity and yet
women do get pregnant. What action of the uterine tubes
helps to direct the oocytes into the woman’s duct system?
Body of clitoris,
Crus of clitoris
Opening of the duct
of the greater
The external genitalia (vulva) of the female.
Superﬁcial structures. The region enclosed by dashed lines is the
Deep structures. The labia majora and associated skin
have been removed to show the underlying erectile bodies. For the
associated superﬁcial muscles, see Figure 10.13 on p. 345.