Download Differentiation

Development From
Conception To Birth


Conception occurs when a
sperm and an ovum unite.
A zygote (0-14 days) is
produced by union of a
sperm and an egg.
Development From
Conception To Birth

The child inherits half of its
genetic makeup from each
parent through meiosis of
46 chromosomes, 23
from each parent.
Development From
Conception To Birth
 Implantation zygote embeds
itself in wall of
uterus and develops
into an embryo (2-9
weeks)
 9-40 weeks =
fetus.
Differentiation development
of cells into tissues and
organs.
 controlled by cell's expression
of genes with environment.

Sexual differentiation

From fertilization - six weeks of
development, male and female
embryos have undifferentiated
gonads (sex glands: ovaries or
testes).
Sexual differentiation
a gene on the Y chromosome
directs the undifferentiated gonads
to become testes.
 If Y chromosome is not present (as
in normal females), undifferentiated
gonads will become ovaries (female
epigenesist)

Fetal period
Gestation = pregnancy
 Full term = 40 weeks
 Viability = ability to survive outside
womb
 Premature birth = prior to 37
weeks or birth weight of less than
5.5 pounds

Development From
Conception To Birth

Despite protection of mother's
body, baby's development may
be influenced by mother's diet,
physical condition, drugs she
may use, including tobacco and
alcohol.
Prenatal Development
Folic acid (vitamin B9 or folate)
important in preventing neural
tube defects such as spina bifida
 crucial in development of DNA.
 plays large role in cell growth and
development and tissue formation

Prenatal Development
400 micrograms (0.4 milligrams)
daily of folic acid
 Mom needs 350 extra calories
daily
 Maintain normal exercise (unless
complications arise)

Alphafetoprotein

AFP is a protein secreted by
the fetal liver and excreted
in the mother's blood.

Elevated AFP in mother’s blood
can indicate neural tube defect
in baby such as spina bifida.
Lower levels of AFP suggest
possible Down’s syndrome or
other chromosomal defect.
Ultrasound
Ultrasound/ sonogram
Amniocentesis
CV Sampling
Chorionic villi are tiny parts of
placenta formed from the
fertilized egg, having same
genes as the fetus.
 CVS can identify chromosomal
problems: Down syndrome,
cystic fibrosis, Tay-Sachs disease
and sickle cell disease

Teratogens
Agents capable of causing
developmental abnormalities
in utero.
 effect related to type of agent,
dose and duration and time of
exposure

Environmental Insults
1. Malnourishment
 Malnourished mother
= malnourished baby
 Miscarriages and
stillbirths

Teratogenic drugs
Anti-nausea - thalidomide
 Prevent miscarriages: Synthetic
hormones - diethylstilbestrol
(DES)—cancer in children
 Alcohol – FAS
 Tetracycline- bone development

Environmental
Insults
2. Alcohol
 Migrating cells go
 TOO FAR
 F.A.S.

Environmental Insults
3. Radiation
 Cells don’t go far enough
 After 8 weeks/ problems
 Mental retardation
 Growth retardation

Environmental Insults
4. Smoking cigarettes
 Poisons and lack of oxygen
 Fetus curls up/ trauma
 Low birth weight/stillbirth
 Fetal Tobacco Syndrome

Teratogens
Cocaine, marijuana – reflexes,
attention, mood (short-term?)
 Rubella – heart/brain defects,
deafness and cataracts/blindness
 Stress – LBW, premature,
miscarriage
 HB Pressure – LBW/ constricted
blood flow to placenta

Development In Infancy

Newborn infants are able to
recognize voices (audition)
and faces (vision), to make
appropriate facial reactions
to taste and smell, and even
to learn.