urethra and anterior to the rectum (see Fig. 20–5).
The vaginal opening is usually partially covered by a
thin membrane called the hymen, which is ruptured
by the first sexual intercourse or by the use of tampons
during the menstrual period.
The functions of the vagina are to receive sperm
from the penis during sexual intercourse, to provide
the exit for menstrual blood flow, and to become the
birth canal at the end of pregnancy.
The vaginal mucosa after puberty is stratified
squamous epithelium, which is relatively resistant to
pathogens. The normal flora (bacteria) of the vagina
creates an acidic pH that helps inhibit the growth
of pathogens (see Box 20–5: Sexually Transmitted
Diseases).
EXTERNAL GENITALS
The female external genital structures may also be
called the vulva(Fig. 20–7), and include the clitoris,
labia majora and minora, and the Bartholin’s glands
(see Fig. 20–5).
The clitorisis a small mass of erectile tissue ante-
rior to the urethral orifice. The only function of the
clitoris is sensory; it responds to sexual stimulation,
and its vascular sinuses become filled with blood.
The mons pubis is a pad of fat over the pubic sym-
physis, covered with skin and pubic hair. Extending
posteriorly from the mons are the labia majora(lat-
eral) and labia minora(medial), which are paired
folds of skin. The area between the labia minora is
called the vestibule and contains the openings of the
urethra and vagina. The labia cover these openings
and prevent drying of their mucous membranes.
Bartholin’s glands, also called vestibular glands
(see Figs. 20–5 and 20–6), are within the floor of
the vestibule; their ducts open onto the mucosa at the
vaginal orifice. The secretion of these glands keeps the
mucosa moist and lubricates the vagina during sexual
intercourse.466 The Reproductive Systems
BOX20–5 SEXUALLY TRANSMITTED DISEASES
simplex (usually type 2). Painful lesions in the geni-
tal area are the primary symptom. Although the
lesions heal within 5 to 9 days, recurrences are pos-
sible, perhaps triggered by physiological stresses
such as illness. Although herpes is not curable at
present, medications have proved useful in sup-
pressing recurrences. It is estimated that 2 million
new cases of genital herpes occur every year.
Neonatal herpesis infection of a newborn dur-
ing passage through the birth canal. The infant’s
immune system is too immature to control the her-
pes virus, and this infection may be fatal or cause
brain damage. A pregnant woman with a history
of genital herpes may choose to have the baby
delivered by cesarean section to avoid this possible
outcome.
Chlamydial infection—caused by the very
simple bacterium Chlamydia trachomatis. This is one
of the most prevalent STDs in the United States,
with estimates of 4 million new cases yearly.
Infected men may have urethritis or epididymitis.
Women often have no symptoms at first but may
develop PID, which increases the risk of ectopic
pregnancy. Infants born to infected women may
develop conjunctivitis or pneumonia. Chlamydial
infection can be treated successfully with antibiotics
such as erythromycin or azithromycin.Sexually transmitted diseases(STDs) are those
in which the pathogen is acquired during sexual
activity. Most are caused by bacteria or viruses.
Gonorrhea—caused by the bacterium Neisseria
gonorrhoeae. Infected men have urethritis with
painful and frequent urination and pus in the urine.
Women are often asymptomatic, and the bacteria
may spread from the cervix to other reproductive
organs (pelvic inflammatory disease [PID]). The use
of antibiotics in the eyes of all newborns has virtu-
ally eliminated neonatal conjunctivitis acquired
from an infected mother. Gonorrhea can be treated
with antibiotics, but resistant strains of the bacteria
complicate treatment. Despite this, the number of
reported cases of gonorrhea has been decreasing in
recent years.
Syphilis—caused by the bacterium Treponema
pallidum. Although syphilis can be cured with peni-
cillin, it is a disease that may be ignored by the per-
son who has it because the symptoms may seem
minor and often do not last long. If untreated, how-
ever, syphilis may cause severe or even fatal dam-
age to the nervous system and heart. In the last few
years the number of reported cases of syphilis has
been decreasing, and the CDC has hopes of eradi-
cating syphilis in the United States.
Genital herpes—caused by the virus herpes