Transcript Prenatal Development - Scott County Schools

Prenatal Development
A Month at a Time
From Conception to Birth
Conception
A sperm penetrates the egg’s protective
membrane (left and center), then sheds its tail.
The Zygote
After conception takes place, this single fertilized egg
divides: into two identical cells, then four, then eight,
then sixteen and so on.
WEEK 1
Early Pregnancy Factor
24 to 48 hours after fertilization begins,
pregnancy can be confirmed by detecting a
hormone called “early pregnancy factor in the
mother’s blood (The test for this hormone,
however, is not widely available). This
substance helps prevent the mother’s immune
system from rejecting the soon-to-beimplanted embryo and allows pregnancy to
proceed.
Week 1
Implantation
Week 1 Implantation
• The Zygote nestles into the well prepared
endometrium – an event called implantation.
This is the process whereby the early embryo
embeds into the inner wall of the mother’s
uterus. Implantation begins about 6 days after
fertilization and is complete by about 12 days.
• Some of the cells will grow into the placenta:
others will become part of the baby. With
implantation, blood levels of the hormones
progesterone rise in the mother.
Week 1-2
• Approximately 8 days after fertilization, cells
from the growing embryo begin producing a
hormone called human chorionic
gonadotropin or hCG. This hormone is
present in a pregnant woman’s blood and
urine almost immediately and is the substance
detected by most pregnancy tests.
Week 1-2
• Nutrients, oxygen, vitamins, and water in the
mother’s blood stream pass through the
placenta and umbilical cord to the embryo;
while carbon dioxide and other waste flows
back to the mother. The placenta also
produces hormones and maintains fetal
temperature above the mother’s temperature
• A twisting cord of blood vessels, called the
umbilical cord, connects the embryo to the
placenta.
Week 2-3
• Stem cells have divided and differentiated into
3 different germ layers called Ectoderm,
Endoderm, and Mesoderm. Each gives rise to
major components of specific body structures
and organs.
GERM LAYER
Ectoderm
• Brain
• Spinal cord
• nerves
• Skin
• Nails
• Hair follicles
• Sweat glands
• Muscles & bone in face
Endoderm
• Lining of respiratory
• Gastrointestinal
• Lungs
• Liver
• Pancreas
• Intestines
Germ Layers Cont
Mesoderm
• Heart
• Kidneys
• Bones
• Muscles
• Blood vessels
• Reproductive
• Urinary
End of Month 2
At the end of week 8, the embryo becomes a
fetus, measuring about 1 ½ inches.
3-4 Weeks
• Only 3 weeks and 1 day after fertilization – the
heart begins to beat. By 4 weeks, the heart
typically beats between 105 and 121 times per
minute.
•
• Upper and lower limb buds appear by four
weeks
The Arms
Month 2
The Neural Tube
• In the 5th week, the two ends of the long strip
of cells that are the embryo fold in gently. One
fold will become the head. Nerves that will
become the brain have started to form. The
fold at the other end of the embryo will
become the genitals. Between these two
folds are growing the neural tube (the site of
the spinal cord) and a hint of the bones of the
spine that protect the cord.
End of month 2
• The next 3 slides show development at the
end of the embryonic period. The fetus is in
an amniotic Sac, filled with amniotic fluid.
• Notice the fingers are forming.
• The ragged chorionic villi outside the sac will
form the placenta.
• The brain can be seen through the fine skin.
4-5 Weeks
• At this point, the embryo’s skin is only one cell
thick. This makes the skin transparent,
allowing us to see internal organs during early
development.
5- 6 WEEKS
• Embryo begins to move.
6-7 Weeks
• The embryo has brainwaves by 6 weeks, 2 days!
• Hiccups begin
• OLDEST BONES IN YOUR BODY=Bone formation
begins between 6 and 7 weeks, starting with
the clavicle, or collar bone, and the upper and
lower jaw. This process is called ossification.
• By 7 weeks, the ovaries appear in the female
embryo. In the male embryo, a gene on the Ychromosome produces a substance causing the
testes to begin to differentiate.
7-8 Weeks
• The embryo also kicks, and will jump if
startled.
• By 8 weeks the brain is highly developed
The Ear
8-9 WEEKS
• Thumb sucking begins and the fetus may
swallow amniotic fluid
9-10 WEEKS
• By this point, ossification is underway in most
bones.
• Fingers and toes, nails begin to emerge, as do
fingerprints.
10-11 WEEKS
• The nose and lips are completely formed.
• Though gender is determined at fertilization,
genitalia now distinguish male from female.
11-12 Weeks
• No diapers in the womb! = the fetus expels
“waste” directly into the amniotic fluid. (But
remember, the umbilical cord is also removing
waste.)
Month 3
• Nostrils, mouth, lips, teeth buds and eyelids form.
Face is well formed.
• Head is half of fetus’s size.
• Eyelids fuse and do not open until 7 months.
• All organs are present, but immature.
• Genitals differentiate.
• Liver produces red blood cells
• Fetus is 2 1/2 – 3 inches long by end of month 3
and it weighs ½ oz.
Month 3
Month 3
Month 4
• Fetus can suck thumb, swallow , hiccup and
move.
• Facial features are clearer
• Lanugo (fine hair) develops to help keep fetus
warm
• Practices breathing
• Liver and pancreas produce fluids
• Skin is transparent
• Bones are getting harder
Month 4
• Baby movement can be felt by mother, which
is called quickening.
• The body proportions are more like a baby’s
near the end of the 4th month.
• The fetus is about 5 inches in length and 4oz
by the end of the 4th month.
Month 4
Month 5
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Hair, nails, eyelashes and eyebrow appear
Teeth continue to develop
Organs keep maturing
Fetus is active with increase muscle development
Fetal heartbeat can be heard with a stethoscope
Lanugo now covers body and collects Vernix- a
waxy coating to cover and protect the skin.
Month 5
• Mom definitely feels the baby
• Lower airways of lungs present, but not
mature enough for gas exchange
• Baby will wake and sleep
• The nose and ears begin ossification and
skeleton hardens
• Fetus is 6-7 inches long and about 10-12 oz. by
the end of month 5.
Month 5
Month 5
Month 6
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Fat is depositing under the skin
Fetus looks wrinkled
Eyes develop, eyelashes and brow well formed
Can hear mom’s muffled talking, singing and
rumbling of her stomach
• Air sacs in lungs mature but still can’t exchange
gas, breathing movements begin
• Foot and finger prints form
• Fetus is 8-10 inches long and weighs 1 ½ -2 lbs
Month 6
Month 7
10-12 inches long Weighs between 2 1/2 – 3 lbs
Lanugo starts to disappear
Can cry weakly
Suck its thumb
Make reflex movements: startle, grasp & swim
movements
Cerebral Hemispheres cover almost the entire
brain
Month 7
• Fetus is active , then rests
• Eyelids separate, open and close
• Nervous system is developed enough to
control some body functions
• Respiratory system (breathing) developed
Month 8
• Fetus may react to noises with a jerking actions
• Fetus has moved to “head down” position, but
can turn back to “bottom down”
• Bones are fully developed but soft and pliable
• Rapid increase in the amount of body fat( ½ lb. a
week)resulting in rapid weight gain
• Rhythmic breathing, however, lungs not fully
mature.
• The baby can be 14-16 inches long and weigh 4-6
lbs.
Month 8
Month 9
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Fetal movements slow due to lack of room
Continues with rapid weight gain
Lanugo begins to disappear
Hair is thick
Skin is smooth no longer wrinkled.
Baby acquires antibodies from mother
Fetus descends into the pelvis and is ready for
birth
• 19-22 inches long and weighs 6-9 lbs.
Month 9
Birth!
men
Birth
• 280 days (40 weeks) after the first day of the
last menstrual period the baby is born .