Sex Cells (Also called gametes)
Egg Cell (or ovum)
Sperm Cell
Sex Chromosomes
23 chromosomes in each sex cell
 23rd chromosome is the “sex
chromosome”

Egg cell always carries
the “X” sex
chromosome
 Sperm cell can carry
the “X” or the “Y” sex
chromosome

Which sex cell determines the
gender of the baby?
Genes
 found
 pass
on chromosomes
genetic traits to offspring
will be expressed if one
of the parents has the
gene for that trait.
will be expressed only if
both parents carry the
trait.

Definition: the process of
becoming pregnant
including fertilization

Starts with two tiny cells
(sperm and egg) that
join together to grow
into a baby
Fertilization
The strongest, fastest healthiest sperm
have the best chance of fertilizing the egg

Or
maybe the
most charming…
Clip
How does a woman know if
she is pregnant?
Missed period
 Breast tenderness or fullness
 Nausea and sometimes vomiting
 Changes in appetite
 Urination
 Tiredness

Pregnancy Tests
 Urine
test – tests for
pregnancy
hormone, HCG
 Pelvic
exam –
checks for
enlarged cervix

Single cell formed
at conception by
union of sperm
and egg

Contains genetic
material from
both parents
From Zygote to Embryo

Zygote divides into a multi-celled mass
called an embryo as it travels down the
fallopian tubes
Embryo searches for a place to implant in
the uterine lining, or endometrium
It actually burrows beneath the surface
Actual image of implantation

After about two months, the embryo takes
on a human appearance and is now
called a fetus.
EMBRYO
FETUS
Click the photo to see the first few
weeks of development.
Formation of Twins
Identical



One egg and one
sperm
Zygote divides and
separates into two
Each have the same
DNA
Fraternal


Two eggs and two
sperm
Each have different
DNA

Grows from the
outer edges of the
embryo

Connects embryo
to uterine wall

Filters nutrients and
waste between
mother and baby
Grows between
placenta and baby
 Provides baby with
oxygen and nutrients

Amniotic Sac

Thin, but strong, membrane filled with
fluid that cushions and protects the
fetus and regulates its temperature
How can smoking during a
pregnancy affect the baby?
After birth:

In the womb:




Low birth weight
Stillborn baby
Increased risk of
birth defects
Premature birth



Asthma and
breathing
problems
Increased risk of
SIDS
Affects physical
and intellectual
growth
Behavioral
problems
Did You Know?

Pregnant women who use drugs such
as heroin, cocaine, marijuana, PCP,
methadone, and/or amphetamines
may give birth to drug-addicted
babies.
How does alcohol use affect
the baby?
Increased risk of miscarriage
 Birth defects
 Fetal Alcohol syndrome (FAS)
- facial abnormalities
- malformations of the heart
- growth retardation
- mental disorders

“Water breaks” - amniotic sac bursts, the
fluid is released through the vaginal canal
 Contractions - uterine muscles give
cramping sensation as cervix starts to
dilate
 Either one could happen first!

Birth
 Natural
birth - Baby is pushed out
through birth canal (vagina)
 Caesarian section – Baby is removed
from uterus via surgery
Click the photo to see how the baby
makes its way out of the womb.
First Breath
The hole in the heart will
close, changing the heart
from a one-pump heart to a
two-pump heart.
The linking passage outside the heart will close
off and force oxygenated blood to the lungs so
the baby can take its first breath.

Umbilical cord
ceases working and
is cut and clamped

Placenta detaches
from the side of the
uterus and is pushed
out