Aquila Children's Magazine AQUILA Magazine Best Bits | Page 73

EMBRYO STAGE
Uterine cavity
Your parents’ combined DNA blended
to make a new single cell called a
zygote, which contained the code
for your own unique DNA and the
instructions for building your entire
body. Your original single cell copied
your DNA code and split apart into
two cells, this took roughly 24 hours.
Your cells continued copying and
splitting and by the end of the third
day, you were a multi-celled ball that
looked a little like a tiny mulberry.
You passed through the fallopian
tube and attached to the uterus wall,
you formed your own placenta and
amniotic sac, and then tiny, multi-
celled-ball-you started fl oating in
amniotic fl uid.
Your 3-week-old embryo was 2–3 mm
long and your neural tube (later to
be your spinal column) was formed.
At 4 weeks from conception you
were 4–5 mm long and your four-
chambered heart started beating!
Just 8 weeks after your single cell
was formed, most of your major
development had occurred and all
your major organs and body parts
were formed. Your embryo was
25–30 mm long (about the size of a
raspberry), your face and neck had
taken shape and you started to move.
Zygote
Amniotic
sac
Placenta
Yolk sac
Maternal blood supply
ECHOES OF EVOLUTION
During the second week of your embryo
development, you developed a yolk sac,
a relic left behind by ancestors who laid
eggs. In your fourth week you resembled
a fi sh embryo. During your fi fth week
you resembled a chick embryo. By
your seventh week you were clearly a
mammal, with a small tail.
form. You carry the story of evolution in
your DNA.
FOETAL GROWTH
Yep, a tail! And by week eight, your
embryo had evolved to your human Your body grew larger and stronger as
you evolved in the womb and your brain
grew rapidly in the last three months.
Your growth was determined by your
inherited genes, your placenta and the
nutrition passed to you by your mother.
You grew from a single cell into a fully-
formed baby made up of trillions of cells
in just nine months!
WEeK 16 WEeK 39
What? Ed
Squash
eapple
Pin
Pumpkin
ermelon
Wat
ulifl ower
Ca
Neural
tube
Uterus
wall
WEeK 7
g
uber in
Fallopian (uterine) tube
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42