863
CHAPTER TWENTY-TWO
Reproductive System
been made of such varied substances as beeswax, lemon
halves, paper, and opium poppy F
bers.
Chemical Barriers
Chemical barrier
contraceptives include creams, foams, and
jellies that have spermicidal properties. These chemicals
create an environment in the vagina that is unfavorable for
sperm cells (F
g. 22.35
c
).
Chemical barrier contraceptives are easy to use but have
a high failure rate when used alone. They are more effective
when used with a condom or diaphragm.
Rhythm Method
The
rhythm method
(also called timed coitus or natural fam-
ily planning) requires abstinence from sexual intercourse
two days before and one day after ovulation. The rhythm
method results in a relatively high rate of pregnancy because
accurately identifying infertile times to have intercourse is
difF cult. Another disadvantage of the rhythm method is that
it requires adherence to a particular pattern of behavior and
restricts spontaneity in sexual activity.
The ef
ectiveness oF the rhythm method can increase by measuring
and recording the woman’s body temperature when she awakens
each morning For several months. Body temperature typically rises
about 0.6°± immediately Following ovulation. However, this tech-
nique does not work For all women. More helpFul may be an “ovula-
tion predictor kit” that detects the surge in LH preceding ovulation.
PRACTICE
57
Why is coitus interruptus unreliable?
58
Describe the idea behind the rhythm method oF contraception.
59
What Factors make the rhythm method less reliable than some
other methods oF contraception?
Mechanical Barriers
Mechanical barriers
prevent sperm cells from entering the
female reproductive tract during sexual intercourse. The
male condom
is a thin latex or natural membrane sheath
placed over the erect penis before intercourse to prevent
semen from entering the vagina upon ejaculation. A
female
condom
resembles a small plastic bag
(fig. 22.35
a
)
. A
woman inserts it into her vagina prior to intercourse. The
device blocks sperm from reaching the cervix. A condom is
inexpensive, and it may also help protect the user against
contracting sexually transmitted infections and prevent the
user from spreading them. However, some men often feel
that a condom decreases the sensitivity of the penis during
intercourse. Also, its use interrupts the sex act.
Another mechanical barrier is the
diaphragm.
It is a cup-
shaped structure with a fl exible ring forming the rim. The
diaphragm is inserted into the vagina so that it covers the
cervix, preventing entry of sperm cells into the uterus (F g.
22.35
b
). To be effective, a diaphragm must be F tted for size
by a physician, inserted properly, and used in conjunction
with a spermicide applied to the diaphragm surface adjacent
to the cervix and to the rim of the diaphragm. The device
must be left in position for several hours following sexual
intercourse, and can be inserted into the vagina up to six
hours before sexual contact.
Similar to but smaller than the diaphragm is the
cervi-
cal cap,
which adheres to the cervix by suction. A woman
inserts it with her F ngers before intercourse. Cervical caps
have been used for centuries in different cultures and have
FIGURE 22.35
Devices and substances used For birth control
include (
a
) male and Female condoms, (
b
) a diaphragm, (
c
) spermicide
in ²
lm, sponge, suppositories, gel (
d
) oral contraceptive, and (
e
) an IUD.
(a)
(b)
(c)
(d)
(e)
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