OBJECTIVES You will be able to Investigate the 3 periods of prenatal development Identify and describe the major components of the 3 periods of prenatal development TRIMESTERS Human gestation ID: 646370
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Slide1
Prenatal Stages of Development
OBJECTIVES
You will be able to….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide2
TRIMESTERS
Human
gestation
or pregnancy lasts about 40 weeks, counting from the first day of your last normal period. The weeks are grouped into three trimesters (TREYE-mess-
turs
).
1
st
TRIMESTER= Weeks 1-12
(
germinal &embryonic & fetal)
2
nd
TRIMESTER= Weeks 13-28
(
fetal
)
3
rd
TRIMESTER = Weeks 29-40
(
fetal
)Slide3
The Germinal Period: The First 14 Days
The
zygote
travels down the
fallopian tube
The
zygote
duplicates and multiplies
When it grows to about 100 cells it is called a
blastocyst
At about a week the 100 cells in the
blastocyst
separate into two distinct masses
The outer cells become the placenta
The inner cells form a nucleus that will be the embryo Slide4
ZYGOTESlide5
BLASTOCYSTSlide6
The Germinal Period: The First 14 Days
When the
blastocyst
embeds itself into the
endometrium
of the
uterus
,
implantation
has occurred.
The organism will not become an
embryo
until
implantation
is successful.
About ½ of all conceptions fail to grow or implant properly and thus do not survive the germinal periodSlide7
IMPLANTATION
http://www.babycenter.com/fetal-development-images-3-weeks
Objectives: SWBAT….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide8
The Germinal Period: The First 14 DaysSlide9
The Germinal Period: The First 14 DaysSlide10
The Germinal Period: The First 14 DaysSlide11
Summary: Germinal PeriodLEFT HAND SIDE
In your own words, summarize what the GERMINAL period means to you.
Objectives: SWBAT….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide12
The Embryonic Period: From the 3rd
through 8
th
week
The formless mass of cells becomes a distinct being
Embryo
- the developing human from day 14 – day 56
A thin line ( called the
primitive streak
) appears down the middle of the
embryo
This will become the
neural tube
at day 22 and will eventually develop into the
central nervous system
,
brain
and
spinal column Slide13
Neural Tube
http://php.med.unsw.edu.au/embryology/images/5/5f/Neuraltube_001.mp4
http://php.med.unsw.edu.au/embryology/images/6/68/Human_embryo_tomography_Carnegie_stage_17.mp4Slide14
Think, Write, Pair, ShareLEFT HAND SIDE
Why do you think the central nervous system, brain, and spinal column are the first things to form?
Write answer IN YOUR OWN WORDS pair up and share with partner
Objectives: SWBAT….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide15
Pregnancy Month by Month
http://www.babies.sutterhealth.org/babygrowth/fetaldev/Slide16
The Embryonic Period: From the 3rd
through 8
th
week
The head appears the fourth week as eyes, ears, nose and mouth start to form
A tiny blood vessel that will become the heart beings to pulsate around the fourth week
Arm and leg buds emerge around the fifth week
Upper arms, then forearms, palms and webbed fingers grow
Legs, knees, feet and webbed toes can be seen a few days later
Each have the beginning of a skeletal structure
Day 52-54 the fingers and toes separateSlide17
The Embryonic Period: From the 3rd
through 8
th
week
The head develops first in a
cephalocaudal
pattern- Head to Tail
The extremities (arms and legs) grow in a
proximodistal
pattern- Near to Far
At the end of 8 weeks, embryo weighs about 1 gram and is 1 inch long.
It has all basic organs and body parts (except sex organs)
It’s movements are frequent about 150 times per hour but such movement is random and imperceptible. Slide18
http://embryo.soad.umich.edu/carnStages/stage20/stage20.htmlSlide19
INTERESTING STUFF! On left hand side
Write down something
interesting
or
surprising
that you learned about the EMBRYONIC PERIOD
Objectives: SWBAT….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide20
The Embryonic Period: From the 3rd
through 12
th
weekSlide21
The Embryonic Period: From the 3rd
through 12
th
weekSlide22
The Embryonic Period: From the 3rd
through 12
th
weekSlide23
The Embryonic Period: From the 3rd
through 12
th
weekSlide24
Summary: EMBRYONIC PERIODon left hand side
Write down IN YOUR OWN WORDS a summary of what the Embryonic Period means to you.
Objectives: SWBAT….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide25
The Fetal Period: From the 9
th
Week Until
Birth
The organism is called a
Fetus
from the ninth week after conception until birth
If the fetus is a male (XY) the SRY gene triggers the development of male sexual organs, otherwise female organs develop
The male fetus experiences a rush of the hormone
testosterone
By the end of the third month, the sex organs are visible via
ultrasound
(sonogram) which uses sound waves to instead of radiationSlide26
Formation of the Genitals
http://www.aisia.org/document/web/girl_and_boy/www.sickkids.ca/childphysiology/cpwp/genital/genitaldevelopment.htmSlide27
Male gender
With the male fetus, the genital tubercle usually creates an angle of greater than 30° with the lower part of the spine.Slide28
Female gender
In the female fetuses, the genital tubercle protrudes in the same direction as the lower portion of the spine with an angle of less than 30° relative to the backbone.Slide29
The Fetal Period: From the 9th
Week Until Birth
The head of the fetus comprises about half of the total body weight
Facial features appear human in placement and shape by the third month
In the fourth, fifth, and sixth months the heartbeat becomes stronger
Digestive and excretory systems develop
Fingernails, toenails and teeth buds form and hair starts to grow (even eyelashes!)Slide30
14 week fetus Ultrasound
http://www.youtube.com/watch?v=WLXpXYo7arM&feature=relatedSlide31
The Fetal Period: From the 9th
Week Until Birth
Age of Viability-
When a pre-term newborn can survive outside the womb
22 weeks is the current
age of viability
- with intensive medical treatment
Even with the most advanced technology, life cannot be maintained without some brain response.
As the brain matures and axons connect, the organs of the body begin to work in harmonySlide32
QuestionTHINK- WRITE-PAIR-SHARE
22 week is the current age of viability, with
intensive medical treatment…
What do you think a fetus that under developed would need to survive outside the womb?
Objectives: SWBAT….
Investigate the 3 periods of prenatal development
Identify and describe the major components of the 3 periods of prenatal developmentSlide33
The Fetal Period: From the 9th
Week Until Birth
The brain increases about six times in size
Half a million brain cells are created per minute
Might be the most important and crucial period for brain development
The entire central nervous system becomes responsive during mid-pregnancy (4-6 months)
Basic body functions like breathing, sucking, are regulatedSlide34
The Fetal Period: From the 9th
Week Until Birth
Age of Viability –
Only means life outside the womb is
possible…
Intensive newborn care is necessary to keep the neonate alive, healthy, and free of disabilities.Slide35
The Fetal Period: From the 9th
Week Until Birth
The last three months of prenatal life, the lungs begin to expand and contract
The fetus begins to exercise breathing muscles by swallowing amniotic fluid as a substitute for air
Heart valves mature
Arteries and veins throughout the body also matureSlide36
World’s Tiniest Babies
http://www.cbsnews.com/2300-204_162-10010544.htmlSlide37
The Fetal Period: From the 9th
Week Until Birth
The relationship between the mother and child intensifies during the final three months
The mother’s sounds, tastes for food, and behavior patterns become part of the fetal consciousness
Auditory communication from mother to child begins at the 28
th
week and improves each week as fetal hearing becomes more acuteSlide38
The Fetal Period: From the 9th
Week Until Birth
The fetus startles and kicks at loud noises
Listens to mother’s voice and heartbeat
Is comforted by rhythmic music and movement
If the mother is fearful or anxious, the fetal heart beats faster and body movements increase.