Download The Reproductive System.

Reproduction
and
Development
spermatogonium
primary
spermatocyte
secondary
spermatocytes
spermatids
Meiosis I
Meiosis II
sperm
Differentiation
(a)
HEAD
nucleus
tail sheath
mitochondria
flagellum
TAIL
(b)
acrosome
MIDPIECE
egg
secondary
oocyte (egg)
oogonium
primary
oocyte
polar body
polar body
polar body
polar body
Meiosis I
Meiosis II
(after fertilization)
(b)
(a)
fimbriae
uterine
tube
ruptured
follicle
fimbriae
corpus luteum
4
ovulated
secondary
oocyte
(egg)
degenerating
corpus
luteum
ovary
ovary
uterus
3
mature
follicle
with
secondary
oocyte
2
developing
follicles
1
new follicle
containing primary
oocyte
progesterone 6
LH
3
9
1
FSH
1
4
estrogen
7
developing
follicle
2
corpus
ovulation luteum
5
menstruation
8
day of menstrual cycle
secondary oocyte (egg)
(a)
corona radiata
zona pellucida
(b)
Stages of development
A. Cleavage
1. Zygote divides without an increase in size
2. A solid round ball of cells called the morula is formed
3. The morula develops a cavity producing a hollow blastula
B. Gastrulation
1. Blastula cells migrate to form three tissue layers
a.
Endoderm, ectoderm, and mesoderm
2. Resulting three-layered embryo is called the gastrula
(a)
(b)
day 3
day 2
day 4
blastocyst
day 1
4 cells 2 cells
zygote
day 7
fertilization
embryo
day 0
blastocyst
implanting
muscle layer
endometrium
ovulated egg
uterine walls
Human prenatal development
A. Implantation of embryo in endometrium
1.
Over half of all embryos fail to implant
2.
hCG (human chorionic gonadotropin), basis
of early pregnancy test
morula stage
cavity
inner cell mass
outer cell layer
blastocyst
(blastula stage)
uterine lining
(endometrium)
embryonic disc
(future embryo)
yolk sac
uterine lining
(endometrium)
amnion
The opening inside the
blastula is the blastocoel.
yolk
The blastopore is
the site at which
gastrulation will
begin.
(a) The blastula just
before gastrulation.
future brain
primitive
gut
(e) Further development. The neural tube differentiates
into brain and spinal cord. A future mouth is produced
when the opening formed by the primitive gut breaks
through at the end of the embryo opposite
the blastopore. The blastopore is the
future anus.
spinal cord
notochord
future
mouth
blastopore
(future anus)
remnant of yolk
Stages of animal development
C. Organogenesis
1. Induction promotes cells to differentiate into
specific organ and tissue types
2. Adult structures develop—programmed cell
death
a. Some cells die unless they receive a chemical
"survival signal"
b. Some cells live unless they receive a chemical
"death signal"
Human prenatal development
B. Early embryonic development
1.
Rapid differentiation and growth during first 2
months
2.
Placenta develops
a) Outer cells of blastula form the chorion, which
penetrates the uterine lining and develops into the
placenta
b) Placenta functions
1) Secretes hormones—estrogen and progesterone
2) Regulates exchange of material between the mother
and the fetus
Age (weeks)
1
2
zygote to formation of embryonic disc
primitive
streak
Zygote cleaves;
blastocyst implants
Two-layered embryo
forms; amniotic cavity
pool of
fetal
chorionic maternal maternal maternal
blood
capillaries villi
arteriole venule
fetal
umbilical
vein
umbilical cord
fetal
umbilical
arteries
fetal
amnion
fetal
chorion
lining of uterus
(endometrium)
uterine
muscle
Human prenatal development
The Placental Barrier
The placenta provides only partial protection
1)
Smoking and pregnancy
2)
Fetal alcohol syndrome
3)
The impact of drugs on fetal development
Age (weeks)
3
4
embryo
2-3 mm
Gastrulation occurs;
notochord and
beginning of neural
tube form
4 mm
Neural tube closes;
heart beats; arm buds,
tail, and gill grooves
Age (weeks)
6
5
embryo
8 mm
Incipient eye parts —
retina (as optic cup) and
lens (as lens pits) — form;
leg buds form; brain
enlarges
13 mm
Webbed fingers and
external ear form;
pigment appears in
retina; tail and gill
grooves
disappearing
gill grooves
5th week
8 mm
arm bud
leg
bud
tail
(a)
umbilical
cord
brain
Age (weeks)
7
8
embryo
18 mm
30 mm
Webbed toes form;
bones begin to harden;
back straightens;
eyelids form
Upper limbs bend at
elbows; genitalia begin
to differentiate; fingers
are distinct
30 mm
8th week
umbilical
cord
placenta
(c)
amniotic sac
Age (weeks)
9
10
fetus
50 mm
61 mm
Toes separate; eyelids
develop; major parts of
brain are present
Chin grows; nostrils
separate; face appears
human; genitals appear
male or female
Human prenatal development
C. Fetal development
1. After two months, the major organs have
formed and the human form appears
2. Gender development in the third month
3. Last 7 months—protected growth and
development period
Age (weeks)
11
12
fetus
73 mm
87 mm
Well-defined neck appears; genitalia are
complete; sucking reflex appears
Age (months)
4
5
fetus
140 mm
190 mm
Blood cells form; all major organs form; head and
body hair appear; movements are felt by mother
Age (months)
6
7
fetus
230 mm
270 mm
Fetus may be viable if born; eyelids open; lungs
and lung circulation develop; may suck thumb;
fat deposited under skin
Age (months)
8
9
fetus
300 mm
350 mm
Fetus usually viable if born; fat deposits increase;
body hair is lost; head hair is well developed; most
senses are well developed; fetus turns head down
in uterus
1
The baby is oriented
head downward,
facing the mother’s
side. The cervix is
beginning to thin
and expand in
diameter (dilate).
2
The cervix is
completely dilated to
10 centimeters
(almost 4 inches
wide), and the baby’s
head has entered the
vagina, or birth canal.
The baby has rotated
to face the mother’s
back.
3
The baby’s head
is emerging.
4
The baby has
rotated to the side
once again as the
shoulders emerge.
Birth Control
Methods of contraception
1. Abstinence—100% effective
2. Permanent contraception
a. Sterilization
1) Vasectomy
2)
Tubal ligation
3. Temporary contraception
a. Preventing ovulation
1) Birth control pills
a) High doses of estrogen/progesterone
prevent ovulation
b) Extended use—Norplant and Depoprovera
b. Preventing sperm and egg union
1) Condoms (male and female)
2) Diaphragm and spermicide
3) Rhythm method (natural family
planning)
c. Preventing implantation of fertilized
eggs
1) Intrauterine device (IUD)
4. Abortion
a. Partial birth abortions
b. Chemically induced abortion—RU-486,
methotrexate
Sexually transmitted diseases
(STDs)

A. STD statistics (United States)
•
•
•
1. One in five infected
2. 12 million new STD infections per year
3. Two-thirds of all infections in people under
25 years old, one-fourth of all infections in
teenagers
Sexually transmitted diseases
B. Bacterial STDs
1. Gonorrhea (Neisseria gonorrheae)
a. Infects 2 million per year (United States)
b. No immunity to repeat infections
c.
Can result in sterility
2. Syphilis (Treponema pallidum)
a. 43,000 cases in 1995 (United States)
b. Untreated can result in organ and CNS destruction
c.
Tuskegee Experiment—1932, Macon County, Ga.
3. Chlamydia (Chlamydia trachomatis)
a. Most prevalent of all STDs—over 5 million per year infected (United
States)
b. Serious reproductive tract complications in women - Sterility and
ectopic pregnancy
c. A "stealth" infection—50% of infected are completely asymptomatic
Sexually transmitted diseases
C. Viral STDs
1. Genital herpes
a.
b.
c.
d.
44 million Americans infected (1 in 5 over 13 years old, United States)
No cure, lasts for life
Transmitted to infants, causes severe disabilities
Increases risk of AIDS
2. Genital warts
a. Human papilloma virus
b. 40 million Americans infected
c. 90% of cervical carcinomas caused by HPV
3. AIDS (acquired immunodeficiency syndrome)
a. 4 million diagnosed AIDS cases in past 15 years (worldwide)
1) 400,000 diagnosed infections (United States), possibly 800,000 infected
Sexual disorders

A. Infertility
•
•
•
1. One in six couples unable to conceive
2. STD infections (PID) main cause of infertility
3. Reproductive technologies
•
•
a. In vitro fertilization—26,000 test tube babies
b. Fertility drugs and multiple births