872
UNIT SIX
22.7
BIRTH CONTROL (PAGE 862)
Birth control is the voluntary regulation of the number of
children produced and the time they are conceived. This
usually involves some method of contraception.
1. Coitus interruptus
a. Coitus interruptus is withdrawal of the penis from
the vagina before ejaculation.
b. Some semen may be expelled from the penis
before ejaculation.
2. Rhythm method
a. Abstinence from sexual intercourse two days before
and one day after ovulation is the rhythm method.
b. It is difF
cult to predict the time of ovulation.
3. Mechanical barriers
a. Males and females can use condoms.
b. ±emales use diaphragms and cervical caps.
4. Chemical barriers
a. Spermicidal F
lm, sponges, suppositories, foams,
and gels are chemical barriers to conception.
b. These provide an unfavorable environment in the
vagina for sperm survival.
5. Combined hormone contraceptives
a. A fl
exible ring inserted deep into the vagina, a
plastic patch, or pill can deliver estrogen and
progestin to prevent pregnancy.
b. They disrupt the normal pattern of gonadotropin
secretion preventing follicle maturation, ovulation,
and the normal buildup of the uterine lining.
c. When used correctly, combined hormone
contraceptives are almost 100% effective.
d. Some women develop undesirable side effects.
e. A minipill contains only progestin and must be
taken at the same time daily.
6. Injectable contraceptives
a. Intramuscular injection with medroxyprogesterone
acetate every three months prevents pregnancy.
b. High levels of hormone prevent maturation and
release of a secondary oocyte.
c. Very effective if administered promptly at the end
of the three months.
d. Women may experience side effects; in some
women, use is contraindicated.
7. Intrauterine devices
a. An IUD is a solid object inserted in the uterine cavity.
b. It prevents pregnancy by interfering with
implantation.
c. It may be expelled spontaneously or produce
undesirable side effects.
8. Surgical methods
a. These are sterilization procedures.
(1) Vasectomy is performed in males.
(2) Tubal ligation is performed in females.
b. Surgical methods are the most reliable contraception.
22.8
SEXUALLY TRANSMITTED INFECTIONS
(PAGE 867)
1. Sexually transmitted infections or sexually transmitted
diseases are passed during sexual contact and may go
undetected for years.
2. Many of the sexually transmitted diseases share
symptoms.
b. The most important female sex hormones are
estrogens and progesterone.
(1) Estrogens are responsible for the development
and maintenance of most female secondary
sex characteristics.
(2) Progesterone prepares the uterus for
pregnancy.
2. ±emale reproductive cycle
a. The reproductive cycle is characterized by
regularly recurring changes in the uterine lining
culminating in menstrual fl ow.
b. Menarche is the female’s F
rst reproductive cycle.
c. A reproductive cycle is initiated by ±SH, which
stimulates maturation of a follicle.
d. Granulosa cells of a maturing follicle secrete
estrogens, responsible for maintaining the
secondary sex traits and thickening the uterine
lining.
e. Ovulation is triggered when the anterior pituitary
gland releases a relatively large amount of LH.
f. ±ollowing ovulation, the follicular cells and thecal
cells give rise to the corpus luteum.
(1) The corpus luteum secretes estrogens and
progesterone, which cause the uterine lining to
become more vascular and glandular.
(2) If a secondary oocyte is not fertilized, the
corpus luteum begins to degenerate.
(3) As the concentrations of estrogens and
progesterone decline, the uterine lining
disintegrates, causing menstrual fl ow.
g. During this cycle, estrogens and progesterone
inhibit the release of LH and ±SH; as the
concentrations of these hormones decline, the
anterior pituitary secretes ±SH and LH again,
stimulating a new reproductive cycle.
3. Menopause
a. Eventually the ovaries cease responding to ±SH,
and cycling ceases.
b. Menopause is characterized by a low concentration
of estrogens and a continuous secretion of ±SH and
LH.
c. The female reproductive organs regress.
22.6
MAMMARY GLANDS (PAGE 861)
1. Location of the glands
a. The mammary glands are located in the
subcutaneous tissue of the anterior thorax within
the breasts.
b. The breasts extend between the second and sixth
ribs and from sternum to axillae.
2. Structure of the glands
a. The mammary glands are composed of lobes that
contain tubular glands.
b. Dense connective and adipose tissues separate the
lobes.
c. Ducts connect the mammary glands to the nipple.
3. Development of the breasts
a. Breasts of males remain nonfunctional.
b. Estrogens stimulate breast development in females.
(1) Alveolar glands and ducts enlarge.
(2) ±at is deposited around and in the breasts.
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