Transcript Working with a partner, answer the following questions

Aim: How does an embryo
develop inside the uterus?
Do Now: Explain the difference
between internal and external
fertilization and development.
Which one would produce more
offspring? Explain.
How long are humans pregnant?
Females are pregnant for nine months
or 40 weeks
During this time, the mother and baby
undergo many changes.
Embryonic Development:(Review)
Fertilization
Mitosis
+
Sperm
Egg
Zygote
Embryo- the stage in human
development from the first division of
the zygote until about eight weeks after
fertilization.
Cleavage (Review)
•The term used to
describe the early cell
division associated
with embryonic
development.
•During this time
period, the number of
cells increase
tremendously.
The result of cleavage is an embryo that is …..
Morula
A solid ball of cells which moves
towards the uterus
Mitosis continues & the embryo becomes……
Blastocyst A hollow ball of cells
What happens after fertilization?
The embryo travels to the uterus and
implants itself in the uterus lining
EARLY DEVELOPMENT
• Cleavage occurs
by mitosis
• 4 days the embryo
= 50 cells
• 6-7 days = 100
cells and
• Attaches to the
uterine wall
• (IMPLANTATION)
Cell division continues & the
embryo starts to ….
Gastrula • Fold inwardly
Gastrulation
• Three layers
• Each layer will
eventually form the
different organ systems
• Ectoderm (skin & CNS)
• Endoderm (GI Tract &
lungs)
• Mesoderm (muscle,
bone, blood)
CELLULAR DIFFERENTIATION
• Due to gene
expression, cells
undergo cellular
differentiation, in
which the cells become
increasingly
specialized in structure
& function.
Embryo vs. Fetus
Fetus
Embryo
(Fertilization-8 weeks) (8 weeks-Birth)
Once the embryo becomes a fetus, all
the major organs have begun to form.
Where does the embryo develop?
• In the uterus - womb
• Surrounded by an amniotic sac &
fluid for protection from shock
Why is the fetus floating in a fluid?
The fetus is surrounded
by amniotic fluid and it
helps absorb shock
What does a developing embryo
need?
1. Nutrients for
ATP & to build its
own body parts
2. Oxygen for ATP
Embryonic Waste Products
1. Metabolic waste
(from cells)
2. Carbon Dioxide
Fetal Blood Supply
The blood from the mom and the
embryo NEVER mix. Materials diffuse
between the mother’s blood & the
baby’s blood.
Umbilical Cord
The umbilical cord is responsible for
carrying nutrients and oxygen to the
developing fetus, and waste away.
Placenta
The placenta is the organ that allows
for the exchange of nutrients and
wastes (DIFFUSION OF NUTRIENTS)
STRUCTURES BY 3rd WEEK
• http://www.ehd.org/movies
.php?mov_id=9
• Placenta
• Nervous and
endocrine system
(starting)
• Vital organs
forming
• Heart is beating
FIRST TRIMESTER (3months)
• Most major organs
formed
• Umbilical cord
formed
• Muscular system
developed
• Reflexes
• Amnion formed
SECOND TRIMESTER
•
•
•
•
Tissues become specialized
Skeleton forms
Strong fetal heartbeat
At ~6 months the baby can
live outside the mom with
life support
3rd Trimester
• Fetus doubles in size
• Lungs are forming
• Sleeps 90-95% of the
time
• Dreams
• Premature if born
before 8 months
What happens at around 9 months?
The fetus has developed
all its organs and is ready
to live in the outside
world
The uterine muscles
begin to contract and the
baby is forced out of the
mother.
This process is called: Labor
Prenatal care
•
•
•
•
Good nutrition
Moderate exercise
No smoking
No drugs,
prescription or illegal
• No alcohol
Don’t get morning sickness:
Thalidomide (1950)
Fetal Alcohol Syndrome (FAS)
Consuming
Includes:
alcohol during
•Low
birth weight
development
can
cause
FAS
which
•Small cranium
has disastrous
•Organ
dysfunction
affects on
the
CNS.
•Failure to thrive
•Developmental delays
What trimester is the most
dangerous?
The first trimester,
because all the organs
are forming at this time.
Dangerous chemicals
can affect cell division.