HDFS 129 - Narrative Chapter Three 1
Use these notes in addition to reading the text, to be able to fill in the term lists. In
this review, if I think something is adequately covered in the term list or the
chapter, I won’t go over it here.
Ovaries – There are two of them in a female – They contain thousands of immature egg
Normally, one egg cell matures each month, and bursts out of its follicle (membrane sac)
about two weeks before an expected menstruation. That process is ovulation.
From the ovary, the ovum moves into the Fallopian tube.
Fallopian tubes – are very thin, about four inches long; the tubes lead from the ovaries to
Uterus – muscular pouch that is designed to hold a developing baby
Cervix – opening at the bottom of the uterus – allows penetration of sperm, and delivery
Ovum – female gamete - largest human cell - only “lives”, or is viable and capable of
being fertilized, for about 24 hours – sometimes less
Sperm – male gamete – one of the smallest human cells – much smaller than the egg –
Sperm is capable of independent locomotion, because it has a tail-like structure that
allows it to swim forward through the vagina, cervix, uterus, and into the Fallopian tubes
Sperm also have a short life span – maybe 2 – 6 days – can best fertilize the egg early in
Conception – ovum unites with sperm – usually takes place in Fallopian tube – results in
a single cell which now is back up to the 23 pairs of chromosomes, or 46 total
chromosomes – all the genetic information needed for the development of a baby
Zygote – is the fertilized egg with 23 pairs of chromosomes. As soon as conception
takes place, we say that we are in the Period of the Zygote.
Period of the Zygote starts at conception and ends about two weeks later.
Zygote starts splitting by mitosis a few hours after forming. As it moves through the
Fallopian tube, enough cells are eventually formed so that a sphere of cells is forming,
with a cavity in the center. In this cavity, on one side will develop a clump of cells that
will eventually become the baby.
Blastocyst is this sphere of cells forming in the period of the zygote.
The blastocyst moves out of the Fallopian tube and into the uterus – floats around there a
while, and then implants into the wall of the uterus toward the end of the second week HDFS 129 - Narrative Chapter Three 2
after conception. The blastocyst burrows down into the lining of the uterus, so that it is
The implantation of the blastocyst into the uterine lining begins the growth of the
placenta, the amniotic sac and amniotic fluid, and the umbilical cord.
Placenta – mass of blood vessels eventually in the shape of a disc – one side is attached
to uterus, other side is attached to baby’s umbilical cord. Through the placenta the baby
receives oxygen, nutrients, hormones, possibly antibodies, possibly toxins from mother,
and waste products from the baby go into the mother’s body for disposal. The transfer is
always through the very thin walls of the blood vessels that lie up next to one another.
The mother’s blood and the baby’s blood are never supposed to actually mix. They only
mix if one of the tiny vessel walls breaks.
Umbilical cord – connects baby to placenta – averages about 20 inches long at birth –
blood flows through at fairly high rate of speed, which keeps the cord fairly stiff, so it is
less likely to knot
Amniotic sac – membrane sac that the baby lies inside of. Filled with watery fluid called
amniotic fluid. It protects the baby from shocks and bumps and temperature changes.
Once the placenta, umbilical cord, and amniotic sac and fluid are developing, the period
of the zygote ends and the period of the embryo begins.
So the period of the zygote lasts from conception to about two weeks, when implantation
has occurred and the support structures of placenta, umbilical cord, and amniotic sac and
fluid are developing.
Period of the embryo – lasts from end of second week after conception to the end of the
8 week (about end of 2 months) after conception. Extremely rapid formation. Nervous
system head region – spinal cord – develop fastest and first.
- by about end of 3 week after conception, a primitive heart is already starting to
beat (and mother may not even realize she is pregnant yet).
- Spinal cord and future vertebrae develop, and the brain has formed two lobes by
about the end of the 3 week
- Then blood vessels arthconnected to the heart and circulation begins
- By the end of the 4 week, tiny arm buds appear, and then later leg buds appear –
when embryo is about a quarter of an inch long
- During 5 week after conception, arm buds develop upper, and then lower parts,
and finally what are called hand plates, with finger outlines (imagine your hand in
a mitten and you spread your fingers apart). The fingers are not separated yet.
- The same thing is happening to the leg buds – upper and lower parts, then foot
with fused toes. HDFS 129 - Narrative Chapter Three 3
- By end of the 7 week the brain has grown rapidly and bends forward, the baby
has all of the internal organs, and the heart, kidney, liver, and stomach have
- The embryo can move, thd it already has the sense of touch
- By the end of the 8 week the embryo is recognizable as human, and we then say
we have come to the end of the period of the embryo.
Period of the Fetus – from the end of the 8 week after conception to birth of the baby
is called the period of the fetus.
- the sexes differentiate, fingernails and toenails form, and the fetus grows rapidly
- the organ systems are functioning – the fetus can swallow amniotic fluid, and
- the fetus will suck its thumb, move, and has sleep/wake patterns
- in the later months, the fetus has a favorite position, and becomes more active
- the fetus sometimes hiccups, and makes breathing movements
- the fetus in the later months can hear, and develops a fat layer under the skin
Lanugo hair develops somewhere around five months – fine hair that develops all over
the baby’s body, and which usually disappears by birth, or very shortly after. You tend to
see lanugo hair more on premature babies.
Vernix caeseosa forms around six months – cheesy whitish substance that protects the
baby’s skin until birth – looks and feels kind of like noxema cream. Some babies are
born with a lot of it – some with not much of it
Quickening – time when mother first feels the baby move – around 5-6 months
Trimester – period of three prenatal months. Therefore there are three trimesters – first,
second, and third
First trimester is sometimes considered a critical period – everything is developing so
rapidly, that environmental influences – teratogens – can have devastating effects. The
embryonic period is especially considered a critical period.
The last trimester is especially devoted to nervous system development again – the
brain needs to be ready to take over functioning independently and get the child breathing
after birth. The last trimester is also important for growth – addition of length and
weight – Nutrition of the mother is very important in this semester for over all growth,
and for growth and development of brain cells. A fat layer is added, which will help the
baby maintain his body temperature. A full-term infant averages about seven pounds and
20 inches long.
Teratogen – any environmental agent that causes damage to the baby during the prenatal
period. HDFS 129 - Narrative Chapter Three 4
Many teratogens, but not all, act during the critical period of the period of the embryo.
The dose – how much , the age or timing of the administration, the presence of other
negative factors at the same time, and the hereditary makeup of mother and child all can
influence the impact of a teratogen.
Thalidomide is a teratogen – a drug given originally to pregnant mothers with bad
morning sickness – prescribed by doctors – later found that deformed the fetus, causing
arms or legs to not develop.
Diethylstilbestrol – DES – a teratogen – drug prescribed to prevent miscarriage – later
found that the female children, once grown, had high rates of cancer of the vagina,
malformation of uterus, and infertility, and male children when grown had an increased
rate of genital abnormalities and cancer of the testes.
Accutane – a teratogen – drug used to treat acne. If baby is exposed to accutane during
the first trimester, may suffer abnormalities of eye, ear, skull, brain, heart, and immune
Other environmental influences – Illegal drugs – Alcohol, Fetal alcohol syndrome,
radiation, prescribed drugs, others - - Pay attention to text –
Alcohol – mothers who drink alcohol may deliver babies who are somewhere on the
Fetal Alcohol Spectrum. They may have Fetal Alcohol Syndrome (FAS). FAS babies
tend to be small, may go through withdrawal, may show mental retardation, and may
have characteristic facial deformities. They also are apt to show attention deficit disorder,
and impaired learning and impaired language development. Binge drinking, as well as
sustained drinking over time, can lead to damage for the baby.
Smoking – nicotine reduces amount of oxygen getting to fetus – may cause placenta to
not grow properly. Smoking also causes carbon monoxide to be in the blood, which can
damage the central nervous system.
Age of mother – too young and too old have greater incidence of problems
Emotions and stress – The mother’s emotions and stress can trigger hormonal changes
in her body, which may be passed through the placenta to the baby. Stress may also
cause blood flow to the uterus to decrease, which would cut down on oxygen getting to
Nutrition – remember folic acid – any woman who is sexually active should be getting
enough folic acid. If you are not getting enough, and you get pregnant, the baby may
develop neural tube defects – e.g., spina bifida. Remember that the brain and spinal cord
starts to develop very early, in the third week after conception, when the mother may not HDFS 129 - Narrative Chapter Three 5
even know that she is pregnant yet. Folic acid can be gotten from eating fortified cereal,
green leafy vegetables, and/or taking a multivitamin every day.
Caffeine – from whatever source – in large doses may not be good for the baby
Rh incompatability – The Rh factor is a blood protein. If you are Rh negative, your
blood does not have this factor. If you are Rh positive, your blood does have this factor.
If the mother is Rh negative and baby Rh positive and blood mixes for some reason – the
mother starts to make antibodies against what her body figures is a foreign substance.
Once the antibodies get to a high enough level, they can start destroying the baby’s red
blood cells, so he can’t carry oxygen to his cells efficiently. If unchecked, the Rh
incompatability can lead to miscarriage, heart damage, and sometimes infant death. A
substance called rhogam can be given to the mother to help reduce the buildup of
Toxoplasmosis – disease carried by a parasite in animals – pregnant mother can get it if
eats undercooked meat, or cleans a litter box for a cat. Can cause eye damage and
possibly brain damage in the baby. HDFS 129 - Narrative Chapter Three 6
Go over child