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PRENATAL DEVELOPMENT
Chapter 4 PregnancyUnit 2
What you should know when we are done with this chapter!
•Describe what happens during conception•Explain how genetic factors affect prenatal development•Describe how a person inherits traits through genes•List the three different types of multiple pregnancies•Describe the three main stages of prenatal development
The prenatal period lasts from about 270-280 days. It is the
shortest stage in the life span.
What is Pregnancy?
The process through which a new human prepares to enter the world.
Conception:
Cell- the smallest unit of life that is able to reproduce itself. Life begins with the joining of two separate cells one from the male and one from the female
Sperm- the male germ cell Ovum or egg- the female germ cell Conception- the joining of these two
cells- at conception, ovum and sperm combine to form a single cell called a zygote or fertilized egg
Egg information
Eggs produced and stored by the woman’s ovaries in a small sac called the follicle. Each month hormones cause some follicles to grow and fill with fluid. Around the middle of the menstrual cycle, one ovum is released from the follicle and the other follicles become inactive- yet sometimes more than one ovum or egg is released. The release of the ovum from the ovary is called ovulation.
When the egg is released it travels to the fallopian tubes- these are two hollow tubes that extend from the right and left sides of the uterus. Once inside the FT- the ovum or egg is ready and available to be joined by a sperm. Semen may carry over 100 million sperm as it enters the woman. Many of the sperm do not survive. Sperm may meet the ovum at any point. Only one sperm successfully enters or fertilizes the egg. Once one sperm enters- no others can enter and CONCEPTION HAS OCCURRED AND A ZYGOTE IS FORMED!
Uterus- the organ is which the baby develops and is protected until birth
GENETICS- traits passed through genes. These affect ALL stages of
development.
Because of genetics the unborn baby will:
come to look like other family members
likely have the same interests have similar personalities
Genetics affect the prenatal period- and sets forth the blueprint for the developing fetus. These blueprints will give information to the fetus later in life.
For example- during the prenatal period- the blueprint is put down whether the baby boy will become bald later in life- sorry Rogaine!
Chromosomes and Genes
Each baby is given 23 pairs of chromosomes- for a total of 46
½ from mom and ½ from dad- What are they? threadlike structures that carry genes in living cells.
Each chromosome contains about 20,000 genes - these genes determine traits each person will have
Humans cells have about a million genes- sometimes one gene will determine a trait- other times it a group of genes that do
Traits DOMINANT TRAITS- traits that
always show in a person even if only one gene of the pair is inherited for that trait.
RECESSIVE TRAIT- traits that
typically do not show in a person unless both genes for the trait are inherited
Sorry, I couldn’t help myself!
Sex Chromosomes- 22 of the chromosomes the same in men and women- the last pair is the
sex chromosome
How are we doing? Did we?
• Describe what happens during conception
• Explain how genetic factors affect prenatal development
• Describe how a person inherits traits through genes
• List the three different types of multiple pregnancies
• Describe the three main stages of prenatal development
What can be affected by sex chromosomes:
Height Eye color
Multiple Pregnancy-If 2 or more babies develop in the
same pregnancy
becoming more common due to fertility drugs
Multiples According to the text: frequency of twins 1 in 35 3 or more babies in the same pregnancy 1 in
540 Dr.’s often concerned with the health of
multiples Most of these babies are born early and are
underweight Risks can include:
severe vision issues hearing issues mental and developmental disabilities twins are also 5 times more likely to die in their first
year (triplets 10 times)
Fraternal Births- most common when multiple babies develop
from two or more ova- each fertilized with a different sperm Fraternal Facts: may or may not look alike may or may not be the same gender each fraternal twin has their own chorion-
a membrane that surrounds the baby in the uterus
no more similar than any other sibling
Identical Births-children develop from a single ovum that was fertilized by a single sperm. This happens early on and Dr.’s do not know why it splits.
Identical Facts:
if ovum does not totally split, the babies will be conjoined
identical babies have the identical genetic makeup
they are the result of one fertilized egg
similar in appearance fingerprints, footprints, and palm
prints are similar-but not exact
Mixed Types- can be both identical and fraternal if three or more children are born. In order to be a mixed type, the babies must be fraternal and identical. It works with quadruplets as well. There could even be two identical pairs.
Stages in Prenatal Development:
Many things happen between conception and birth. All these changes are called prenatal development. There are 3 stages:
Germinal/Zygote Embryonic/Embryo Fetal/Fetus
Germinal Stage: this is the first stage.
Conception starts the beginning of this
stage.
Germinal/Zygote highlights: Lasts the first 2 weeks of pregnancy. The fertilized egg remains a single cell for
about a day and ½ By day 3 it is a hollow ball of 32 cells This ball of cells then enters the uterus and
floats freely About 10-12 days after conception the ball of
cell embed in the uterus wall The cells continue to divide The chorion and the amnion(amniotic sac)
begin to form The placenta begins to develop against the
wall of the uterus
Germinal/Zygote highlights:
The umbilical cord grows out of the developing child at the site of the navel and connects with the placenta
The umbilical cord contains three blood vessels that connect the child with the placenta
The placenta will develop it will begin to nourish the baby, remove the baby’s wastes, exchange gases between mom and baby
It also provides hormones for the baby This stage ends when the baby can receive
nourishment from the mom
The Embryonic Stage this is the 2nd stage of prenatal development. Experts say that this is the most important stage since almost all body systems develop during this stage.
Embryo Highlights
Lasts until the 8th week When this stage ends, the embryo looks like a small
human The embryo has tiny arms, legs, fingers, toes, and a face All major organs such as heart, brain, and lungs are there Heart begins beating No bones only cartilage Baby now receives both good and bad substances from
the mom through the umbilical cord Baby’s body parts are developing quickly, so passing
harmful substances to the child can affect them for life The mom’s diet needs to full of vitamins and nutrients Mom should avoid: alcohol, drugs, excess caffeine,
smoke, and x-rays
Fetal Stage: this is the 3rd stage. This is when the bone starts to replace cartilage.
This stage starts about week 9 up to delivery.
https://drive.google.com/a/d155.org/?tab=oo#owner/khester%40d155.org
Fetal highlights:
All body parts start to mature Overall size increases By the 4th month the fetus has grown enough
to give the mom’s growing abdomen a pregnant look
Two major milestones- in the 3rd month the parents may be able to hear the heart of the baby and by the 4th -5th month the mom can start to feel the baby(quickening)
The fetus can turn, swallow, and even suck its thumb
Fetal highlights:
Another important milestone- 28 weeks/7 months= the age of viability- when the fetus has a strong chance of surviving outside of the mom if it were to be born now
They still may need special help- yet they have a strong chance of survival
Last 2 months the lungs become stronger and the baby becomes larger
9th month the baby receives immunities from the mom- ex: if mom had chicken pox- the baby will have the chicken pox immunity from the mom
Finally the baby will start to turn head down to prepare for birth
So, did we get it all?
• Describe what happens during conception
• Explain how genetic factors affect prenatal development
• Describe how a person inherits traits through genes
• List the three different types of multiple pregnancies
• Describe the three main stages of prenatal development
