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36.2 Human Development

Before Birth

Bio 30 NWRC

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Fertilization ( find another video)

Ovulation

Fertilization

(occurs in the oviduct)

Implantation in theuterus
http://uk.youtube.com/watch?v=2eelyg_k5iwhttp://uk.youtube.com/watch?v=2eelyg_k5iw

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Fertilization

Only 1 sperm fertilizes

the egg but 100s are

needed to bombard and

break down the eggs

plasma membraneonce the eggs

membrane is weakened

and a sperm penetrates it

the egg forms a barrierwhich does not allow any

other sperm to enter.

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Early Development

Morula

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From One Cell to Blastula to

Blastocyst
http://uk.youtube.com/watch?v=UgT5rUQ9EmQ&NR=1http://uk.youtube.com/watch?v=UgT5rUQ9EmQ&NR=1

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ExtraEmbryonic Membranes

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ExtraEmbryonic MembranesAmnion:A thin, tough,

membranous sac that enclosesthe embryo. It is filled with a fluidin which the embryo issuspended.

Chlorion:The outer membrane

enclosing the embryo in reptiles,birds, and mammals. In placentalmammals it contributes to thedevelopment of the placenta.Yolk Sac: Functions as the

circulatory system of the humanembryo before internalcirculation begins.

Allantois:It is important in theformation of the umbilical cord

and placenta in mammals.

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The PlacentaThe placenta is partially

of fetal origin and partly

of maternal origin The

fetal portion is composed

of highly specialized cells

from the outermost

embryonic membrane,which form projections

that contain the fetal

blood vessels. These

projections are called

chorionic villi. Thematernal portion is

formed by a modification

of the lining of the uterus,

and the fetal villi grow

into the uterine lining

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The umbilical cord inserts into the fetal surface.

Note the vessels radiating out from the cord over

the fetal surface in this normal term placenta.

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The Placenta

Basically, the

placenta is made up

of a combination of

cells from the motherand the growing baby

The mother and the

fetus both have their

own circulatorysystems

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3 Trimesters of Development

FIRST TRIMESTER

At the end of 8 weeks

the embryo is called a

fetus. All the organsystems have begun

to form by the end of

the 1st trimester the

fetus can move andhas fingerprints.

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This little boy is at 9 weeks gestational age of

embryonic life. Note the thin amnionic cavity

surrounding the embryo.

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First Trimester

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Second TRIMESTER

The fetus has now

developed all its

organs and systemsand will now focus on

growing in size and

weight.

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Third TRIMESTER

During the third

trimester, the fetus

continues to grow insize and weight. The

lungs are still

maturing and the

fetus begins toposition itself head-

down.

Link to website: The

Visible Embryo
http://www.visembryo.com/baby/index.htmlhttp://www.visembryo.com/baby/index.htmlhttp://www.visembryo.com/baby/index.htmlhttp://www.visembryo.com/baby/index.html

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Diagnosis in the Fetus

Ultrasound A sonogramprovides images of theinfant in the womb. Itcan be used to

Judge gestation

Measure fetal growth

Evaluate abnormalities

Reveal the sex of fetus

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Amniocentesis: Asample of amniotic fluidcan be withdrawn andanalyzed (fluid contains

fetal cells). It is usefulfor

Diagnosing sex linkeddisorders

Chromosomal defects

Sex can also bedetermined

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Chorionic VillusSampling (CVS)

Tissue is taken frommembrane surrounding

the fetus. Can test for: (1) Chromosomal

abnormalities.

(2) Some inheriteddisorders. Dominant,Recessive and X-linkedpatterns of inheritance.

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Assessment

1. The zygote divides

by mitosis and

becomes a morula

(solid ball of cells)The morula hollows

out and becomes a

blastocyst.

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Assessment

2. The barrier

surrounding the egg

could not be

penetrated andfertilization would not

occur

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Assessment

3. refer to notes-

there is too much

information to

summarize on a slide.

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Assessment

4. During pregnancyprogesterone andestrogen levelsremain highpreventing anothermenstrual period.During a menstrualperiod levels of

progesterone andestrogen drop nearthe end of the cycle.

Documents

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