Anatomy & Physiology 34B
Chapters 27 & 28: Contraception, Conception, & STDs
I. Overview
A. Methods of Contraception
B. Alternative Methods of Conception
C. Sexually Transmitted Diseases
1. Bacterial STDs
2. Viral STDs
II. Methods of Contraception (any procedure or device intended to
prevent pregnancy)
A. Contraceptive methods work in several ways:
1. Behavioral methods
2. Barrier and spermicidal methods
3. Hormonal methods
4. Surgical sterilization
5. Prevention of implantation
B. Behavioral methods include abstinence, the rhythm method, and
the withdrawal method
1. Abstinence, or abstaining from sexual intercourse, is the ONLY
100% sure method of preventing pregnancy and STDs
2. Rhythm method - depends on abstaining from intercourse
during the days near the expected time of ovulation
a. It is difficult to predict the exact time of ovulation
b. A woman monitors her body for a rise in basal body
temperature &/or increase in cervical mucus viscosity
c. Intercourse must be avoided for at least 48 hrs. before
ovulation and 24 hrs. after ovulation
d. This method has a 25% failure rate
e. Has no effect on STDs
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3. Withdrawal (coitus interruptus) - removal of the penis from
the vagina prior to ejaculation
a. Some sperm may be deposited in the vagina prior to
ejaculation (remember the Cowper’s gland?)
b. Like the rhythm method, this also has a 25% failure rate
c. No effect on STDs
C. Barrier methods are meant to prevent sperm from entering the
vagina or the uterus. These are most effective when used with
spermicides that destroy sperm
1. Latex condoms with spermicide for males, when used correctly,
sheath the penis, trap sperm, and help prevent some STDs.
Failure rate is 5-20%
2. Female condoms are polyurethane sheaths with flexible rings on
each end. These are less effective than male condoms because
they do not fit as tightly.
3. Diaphragms & cervical caps with spermicide cover the
female’s cervix, preventing sperm and pathogens from entering
the uterus.
a. Has a 20% failure rate
b. May prevent some STD infections of the cervix, uterus,
oviducts, & ovaries, but not the vagina and vulva
D. Hormonal methods are designed to prevent gamete release
1. Oral steroid contraceptives (“the pill”) - the most widely used
method in the U.S.A.
a. These pills contain a combination of synthetic estrogen &
progesterone (progestin)
b. They prevent follicle development and ovulation by feedback
inhibition of FSH & LH
c. Women stop taking the pill one week of every 3 weeks so the
endometrium can be shed in menstruation
d. Can increase the risk of heart attack or stroke in smokers or
in women with diabetes, hypertension, or clotting disorders
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e. Has a 5% rate of failure
f. The pill does not prevent STDs
2. Norplant - time release capsules implanted under a woman’s
upper arm skin
a. Releases progestin slowly into the blood stream, preventing
pregnancy for up to 5 years
b. Has caused neurological damage in some women
c. Has a 0.05% failure rate
d. Does not prevent STDs
3. Depo-Provera – progestin injected 2-4 times a year.
a. Provides relatively effective, long-term contraception
b. Can cause headaches, nausea, or weight gain in some women
c. Failure rate is 0.3%
d. Does not prevent STDs
E. Surgical Sterilization prevents conception permanently
1. In a vasectomy, a male’s vas deferens are severed, preventing
sperm from entering the urethra during ejaculation. Has no
effect on STDs
2. In a tubal ligation, a woman’s oviducts are severed, preventing
eggs from entering the uterus. No effect on STDs
F. Devices that prevent implantation include:
1. Intrauterine Device (IUD) - small t-shaped object placed in the
uterus by a Dr., prevents embryo implantation.
a. Can cause bleeding, infection, & uterine perforation in some
women
b. Does not prevent STDs.
2. Morning-after pills (Mefepristone=RU-486) - combination of
estrogen & progesterone taken within 3 days after intercourse
a. Causes the endometrium to be shed along with an embryo, if
present (“abortion pill”)
b. No effect on STDs
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III. Alternative Methods of Conception
A. Artificial Insemination, in which semen from a donor is
introduced into the vagina near the cervix, may be employed when
a male is infertile, or when a single woman wishes to conceive
B. Oocyte donation – fresh oocytes are obtained from one woman,
fertilized, and transplanted into the uterus of another woman. Has
a success rate of 20-50%
C. In Vitro fertilization
1. A woman is given gonadotropins (“fertility drugs”) to induce the
formation of multiple eggs
2. The eggs are surgically removed and placed in a chemical
medium with sperm, where fertilization takes place
3. Fertilized preembryos are placed in the woman’s uterus, and her
blood HCG levels are monitored to determine if implantation
has occurred
4. Has only a 14% success rate and cost about $10,000 per try
D. Gamete Intrafallopian Transfer (GIFT) is often used in women
who have obstructions in the fallopian tubes
1. Eggs are obtained from a woman after a week of ovulationinducing drug treatment
2. Active sperm and eggs are introduced into the woman’s uterine
tube, proximal to any obstruction
3. GIFT is less expensive than In Vitro Fertilization and succeeds
about 40% of the time
E. A Surrogate Mother provides a “uterus for hire” to an infertile
couple. The surrogate may
1. Allow In Vitro preembryos from an infertile couple to be
implanted in her uterus, or
2. May be artificially inseminated by the man’s sperm to conceive
a child for the couple.
F. Embryo Adoption, in which a man’s sperm is used to artificially
inseminate another woman, then the preembryo is removed and
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implanted in his wife’s uterus, may be used when the wife has
malfunctioning ovaries but a normal uterus
IV. Sexually Transmitted Diseases
A. Sexually transmitted diseases (STDs) are contagious diseases
spread by sexual contact.
B. Some major STDs caused by bacteria include:
1. Chlamydia - caused by Chlamydia trachomatis, most common
STD in the USA (3-5 mil. cases @ yr.). Symptoms:
a. In males: watery genital discharge, itching, and/or painful
urination
b. Often no symptoms in women or pelvic inflammatory disease
(PID)
c. Can be cured by antibiotics
2. Gonorrhea (“clap” or “drip”) - caused by Neisseria
gonorrhoeae. Symptoms:
a. Males usually experience a pus genital discharge, painful
urination
b. Women often experience vaginal discharge, abdominal pain,
abnormal uterine bleeding and/or PID; 20% of women are
asymptomatic
c. The bacteria can be transmitted to the fetus during childbirth,
causing blindness
d. Most strains can be cured by antibiotics
3. Pelvic Inflammatory disease (PID) is a bacterial invasion of
the female pelvic organs, usually by Chlamydia or Neisseria.
a. May cause the uterine tubes to become scarred and obstructed,
resulting in sterility
b. May require surgical removal of infected uterine tubes or
other reproductive organs
c. Has increased to about a million cases per year in the USA,
rendering thousands of women infertile
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4. Syphilis – potentially devastating disease caused by Treponema
pallidum. Symptoms occur after an incubation period of 2-6
weeks:
a. Primary stage: ulcer (chancre) appears on the genitals, then
disappears in 4-6 weeks
b. Secondary stage: skin rash, fever, joint pain, and hair loss
develop. These symptoms disappear in 3-12 weeks, but can
come and go for up to 5 yrs.
c. Tertiary stage: bacteria spreads through blood causing
cardiovascular and neurological damage, blindness, insanity,
& eventual death
d. Curable by antibiotics in the early stages
C. Some major STDs caused by viruses include:
1. Genital herpes – most common STD in the USA, with 20-40
mil. infected people; usually caused by herpes simplex virus
type 2, but sometimes type 1. Symptoms:
a. Recurring red blisters on the genitals, painful urination, skin
inflammation
b. Virus travels to the dorsal root ganglia and becomes dormant,
but can reemerge several times a year
c. Herpes can be transmitted to a sexual partner whether or not
lesions are present
d. Linked to miscarriage and birth defects
e. Can be treated by Acyclovir, but NO CURE; once you
contract it, you have it for life
2. Genital warts (condylomas) – one of the most rapidly
increasing STDs (1 mil. new cases a yr.); caused by human
papillomaviruses (HPVs). Symptoms:
a. Small painless warts appear on the genitals
b. Some HPVs are strongly linked to cervical cancer in women
c. Genital warts may be treated with cryosurgery, laser surgery,
and interferon, but there’s NO CURE
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3. Acquired Immune Deficiency Syndrome (AIDS)
a. Caused by Human Immunodeficiency Virus (HIV)
1) HIV is a retrovirus consisting of an outer viral envelope
that encloses a matrix around a protein capsid containing
RNA & reverse transcriptase
2) Reverse transcriptase is an enzyme that makes DNA from
the RNA after the virus enters a host cell via endocytosis
3) The viral DNA incorporates itself into the host cell’s DNA
and causes the cell to produce more HIV
b. HIV is transmitted via blood, semen, vaginal secretions, and
breast milk
c. HIV infects and destroys helper T cells, the cells that activate
other T & B lymphocytes responsible for the immune
response
1) A normal helper T cell count is 600-1,200 cells/L of
blood
2) AIDS patients have less than 200 cells/L of blood
d. The incubation period (time from infection to onset of
symptoms) can range from a few months to 12 yrs.
e. Initial symptoms include episodes of chills and fever as HIV
attacks T cells
f. As the virus destroys more cells, symptoms proceed to night
sweats, fatigue, neurological damage, extreme weight loss,
and lymphadenitis
g. Continued destruction of helper T cells leaves the body more
susceptible to opportunistic infections such as pneumonia,
cancer, and other bacterial and fungal infections
h. Worldwide, about 75% of HIV infections are acquired
through heterosexual (predominantly vaginal) intercourse
i. There is no vaccine or cure available, but people can extend
their lives by receiving treatment as soon as possible