Ch 3
Sexual Reproduction
in Humans
Recall:
• Human gametes are produced in the gonads.
• The female gonads are the ovaries, the male
gonads are the testes.
Puberty
Hormones
• Substances which act like messengers
in the body.
• They are made in one part of the body
(in tiny amounts) and travel through
the blood stream causing certain cells
to respond in specific ways.
Puberty (cont’d)
Follicle stimulating hormone (FSH)
• Produced by the pituitary gland at the
base of the brain.
• It is released into the blood in tiny
amounts and travels to the gonads.
In Males
In Females
FSH is received by
testes which begin to
make sperm. Sperm
made daily.
FSH is received by
ovaries which start
maturing and releasing
eggs. 1 egg released
per month.
FSH causes testes to FSH causes ovaries to
start producing the
start producing the
hormone testosterone. hormone estrogen.
In Males
In Females
Secondary sexual
characteristics are
directed by testosterone:
- facial hair
- underarm hair grow
- pubic hair grow
- shoulders broaden
- voice changes
Secondary sexual
characteristics are
directed by estrogen:
- fat deposits in
breasts
- fat deposits on hips
- pubic hair grow
- underarm hair grow
Male Reproductive Anatomy
• Designed to produce 350 – 500 million
sperm a day.
• Scrotum – a sac of tissue which holds the
testes. The sac is outside of the body so it’s
cooler which helps meiosis.
• Seminiferous tubules – are tiny tubes inside
the testes where sperm are produced. Sperm
stay and mature in the tubes for 9 to 10
weeks.
• Epididymis – long coiled tubes outside the
testes. Used for sperm storage.
• Vas deferens – tubes which carry the sperm
out of the epididymis when it’s time to
leave the body.
• Seminal vesicles and prostate gland –
produce thick, milky fluid which is rich in
sugars. The fluid is released into the vas
deferens and provides the sperm with a fluid
in which to swim.
• Semen – a mixture of sperm and sugar rich
fluids.
• Urethra – a single tube from the bladder to
the end of the penis. It carries both semen
and urine. Muscles contract to ensure that
the tube is only used for one thing at a time.
Male Reproductive Anatomy
Diagrams p 82-83
Male Reproductive Anatomy Crossword
Female Reproductive Anatomy
• Purpose: to prepare for fertilization
Parts:
• Ovaries – two almond-shaped organs inside
a woman’s main body cavity where eggs are
stored and mature.
• Ovum – another name for egg. Plural is
ova.
Sperm Pathway
• http://www.argosymedical.com/flash/Sperm
/landing.html
• Ovulation – the process where an ovary
releases 1 ovum every 28 days.
• Follicles – fluid filled cavities inside the
ovary which contains 1 egg each.
• Corpus Luteum – the empty follicle after
the egg has been released. It starts making
hormones.
• Oviducts – (Fallopian tubes) – tiny tubes
which have a hair-like lining move egg
toward the uterus. If sperm are present they
fertilize the egg in the oviducts. The egg
lives for only 24 – 48 hours after ovulation.
• Uterus – a hollow pear-shaped organ with
thick muscular walls.
• Cervix – the lower entrance to the uterus.
• Vagina – a muscular passageway, sometimes
called the birth canal.
• Urethra – the tube which carries urine from
the bladder out of the body. In women it is
separate from the vagina.
• Menstrual cycle – a one month cycle of
changes that surrounds ovulation.
Menstrual Cycle
• lasts about one month.
• prepares the body for the possibility of
pregnancy.
• is controlled by hormones.
Steps:
1) Pituitary releases FSH.
2) FSH stimulates follicles to develop.
3) follicle begins releasing estrogen.
4) estrogen causes:
a) the lining of the uterus to thicken.
b) pituitary gland to release luteinising
hormone (LH).
5) LH causes:
a) the follicle to release its mature egg
(ovulation).
b) empty follicle to develop into a hormone
maker called the corpus luteum.
6) corpus luteum produces progesterone and
estrogen.
7) progesterone causes:
a) thickening of uterus lining.
b) pituitary to decrease FSH and LH
production which prevents another egg from
being released.
8) IF no fertilization:
a) corpus luteum breaks down, decrease
levels progesterone
b) decresed levels of progesterone causes
uterus to shed its lining.
• Menstruation – the breaking down and
shedding of the uterine lining and blood.
Flow lasts about 4 to 7 days. Reduced
progesterone causes pituitary to decrease
FSH. Go to step 1)
Assignment
•
http://www.argosymedical.com/flash/ovulati
on/landing.html
• NOVA Online | Life's Greatest Miracle
• http://health.howstuffworks.com/adamroundup.htm reproduction animations
• Human Reproductive Systems Questions
(P 80-90)
Human Reproductive Systems
Questions (P 80-90)
1. What role(s) do hormones have in the
body? (1)
–
They are chemical messengers in the body.
2. What starts the period of life called
puberty? (1)
–
The pituitary gland releases FSH.
3. Which part of the brain produces FSH? (1)
–
The pituitary gland.
4. FSH has different effects on males and
females. What two things do the testes
produce as a result of FSH? (2)
–
Sperm and testosterone.
5. What are the secondary sex characteristics
for males? (3)
–
Lower voice, facial hair, broader shoulders,
pubic hair, & armpit hair
6. When FSH reaches the ovaries what does
it stimulate? (2)
–
–
Maturation and monthly release of eggs
estrogen
7. Estrogen is a female reproductive
hormone, what secondary sex
characteristics does it bring about in
females? (3)
–
Breast development, broadening hips, pubic
hair and armpit hair.
8. What percentage of women lived to age
15 in Canada in the 1700’s? (1)
–
67%
9. By 1951 this percentage increased to what
number? (1)
–
96%
10. Why do you think this increased so
dramatically? (1)
–
Better health care and nutrition
11. Do questions 1 and 2 on Page 81. (2)
1. The trend in women’s life expectancy
was increased longevity.
2. The trend in the average number of
children born to each woman was a
dramatic decrease from 4.3 down to 1.8.
- a 60% decrease
3.2 Pregnancy
If the egg is fertilized:
• Only one sperm is
allowed to fertilize
it.
• The resulting cell is called a zygote.
• It begins to divide by mitosis 24-36 hours
after fertilization.
• These divisions are called cleavages
• By the time it reaches
the uterus, these
mitotic divisions have
formed a hollow ball
of cells called a
blastocyst.
The outer cells will turn into a placenta and the inner cells will
turn into the embryo.
• 6 – 10 days later the baltocyst reaches the uterus
• The embyro becomes implanted in the thick
uterine lining.
• The embryo releases hormones that cause the
corpus luteum to continue producing progesterone
(uterine lining is not shed)
• identical twins
Embryo Development
After about one week:
• Cells begin to specialize and form a gastrula.
– Three layers of types of cells called germ layers
– Ectoderm forms the skin & nervous system.
– Mesoderm forms the kidneys, muscles, skeleton,
blood vessels, gonads.
– endoderm forms lungs and digestive tract lining.
After 10 – 14 days:
• Outer portions of the embryo form into 4 tissues.
–
–
–
–
yolk sac – nutrients for embryo’s first 2 months
amnion – a sac of fluid around the embryo.
allantois – helps in waste removal.
Chorion – surrounds embryo and grows finger-like
projections filled with blood vessels into the uterus
wall.
• Develops into the placenta which provides the fetus with all of
the oxygen, nutrients and waste removal needs from 2 months
until birth.
• The umbilical cord attaches the placenta with the embryo at the
belly button.
Assignment
• Pregnancy Questions (pages 91 – 94)
• CYU questions 1-5 on page 94.
3.3 Differentiation & Birth
Differentiation and Pre-Natal Development
• The process of cells becoming specialized
to perform specific functions.
Example
• Embryo heart starts beating even though
there is no blood yet.
• embryo is 500 times original size in just 4
weeks.
Trimesters
• A normal pregnancy lasts around 40 weeks
and is called the gestation period.
• Gestation is broken into 3 equal parts of
about 12 weeks each.
First Trimester (weeks 1 – 12)
• At four weeks nerve cells begin to form
• At 8 to 9 weeks the first bone cells begin to
form.
– The embryo is now called a fetus.
• By week 12:
– All major organs have begun to form
– Fetus is about 100 mm long
– Gender can be identified using ultrasound.
Second Trimester (weeks 12 – 24)
• By week 16:
– Placenta is too small to surround the fetus – it moves to
one side.
– Mom begins to feel the fetus move.
• By week 24:
– Fetus is 300 mm long
– Most organs formed but not yet fully developed.
– Fetus still has little chance of survival if born
prematurely.
Third Trimester (weeks 24 – 40)
•
•
•
•
•
•
•
rapid growth
fetus begins to stretch and kick
Immune system develops
Proper nutrition is important for building brain tissue
brain develops rapidly
by 8 months eyes are open
babies are born with an average length of about 500 mm
(21 inches)
• average weight between 2700 and 4100 grams. (~ 7.5 lbs)
Birth
• Sudden dramatic changes in hormone levels
are responsible for starting the birth process.
• There is a sharp drop in progesterone &
estrogen levels causing the uterus walls to
contract.
• The pituitary releases the hormone oxytocin.
This hormone is also used to induce labour.
– It causes:
• The cervix to become thinner
• The uterus to contract
Labour
• Labour can occur when the cervix is thin
enough to allow the baby to move through
it.
• At this point the mother is able to help push
the baby out.
• Some problems that may arise during
childbirth are
– The mother’s pelvis is too small for the baby to
pass through the birth canal.
– The baby may not be in the correct position
(not head first).
• In both of the above cases the baby will be
delivered by cesarean section.
– This involves removing the baby through an
incision in the mother’s abdomen & uterus.
Stages
1. Dilation Stage - waiting for cervix to
dilate or open. Amniotic sac often breaks
releasing amniotic fluid under the pressure
of the uterus. (often known as ‘the water
broke’)
2. Expulsion Stage
–
–
–
–
Uterus contracts more forcefully.
Mom begins to push.
Baby’s head (hopefully looking down) turns
to look over the left shoulder to squeeze
through the Mom’s pelvis.
Baby moves down birth canal and out.
3. Placental Stage
–
–
–
–
a few minutes after Baby is born the placenta
detaches from the inside of the uterus.
Then the placenta and the umbilical cord are
delivered.
http://www.doereport.com/generateexhibit.ph
p?ID=12019l
c-section
Assignment
• Complete Investigation 3-C on pg 99 and do
#1 – 3
• Read & Discuss p 100, 101, 103, 104
• Risk Factors During Development
Questions
• BLM 3-16
• Read Pages 100-101 and do the questions
below.
Research Assignment
• Athletic Amenorrhea (BLM 3-10), FASD, Down’s
Syndrome, Spina Bifida, Placenta Previa, Ectopic
Pregancy, Menopause, Smoking & Pregnancy, Prescription
Drugs & Pregnancy (pain killers, anti-histamines, antinauseants, antacids, anti-diarrhea, constipation, diet pills,
sleeping pills, anti-depressants, antibiotics, allergy meds,
pills for skin problems, etc.), Thalidamide, Cannabis &
Pregnancy, Street Drugs & Pregnancy, Exercise &
Pregnancy, Caffeine & Pregnancy, Sudden Infant Death
Syndrome, Environmental Toxins
• Choose one of the topics listed above (or another
approved topic) and research the following:
–
–
–
–
–
Description
Cause (if known)
Prevention (if possible)
Medical advances
Effects
• http://www.argosymedical.com/flash/Placen
ta_Previa/landing.html
• http://www.argosymedical.com/flash/HPV/l
anding.html