Unit 1 Natural Fertilization

8/17/2019 Unit 1 Natural Fertilization

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Natural Fertilization

• Fertilization refers to the fusion of the egg(ovum) and sperm and usually takes place inthe upper third of the fallopian tubes.

NIH, 2009 Visual by www.PDImages.com


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Natural Fertilization:Video

Video: Hoard Hughes !edical "nstitutehttp:##.hhmi.org#biointeractive#stemcells#human$emb$dev.html

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• nce a month a oman releases an egg during the process ofovulation hich is part of the menstrual cycle.

• vulation is triggered by the release of to hormones by the

pituitary gland (a gland of the endocrine#hormonal system)and usually occurs during day *+ of an average ,-day cycle.

"n humans thefertile phase ortime duringhich a omancan becomepregnant

occurs duringthe fe daysnear ovulation.

NewScientist


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• nce a month a oman releases an egg during the process ofovulation hich is part of the menstrual cycle.

• vulation is triggered by the release of to hormones by thepituitary gland (a gland of the endocrine#hormonal system)and usually occurs during day *+ of an average ,-day cycle.

"n humansthe fertilephase ortime duringhich a

oman canbecomepregnantoccurs during

the fe daysnear

D. Wu, 2007


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• Folloing intercourse during this fertile phase millions ofsperm travel from the vagina to the uterus and into thefallopian tubes.

• &everal thousand sperm reach the egg and one ill fertilizeit.

• /hen the sperm fuses ith the egg it initiates a series of

a!iana "ui# Villa!!eal, 200$

%&a'te& by (uto!Vista.com

)!om *!ey+s %natomy


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0s early as *, hours after fertilization you can see the tobundles of genetic material (to pronuclei) one from eachparent.

1y *-,2 hours after fertilization these pronuclei fuse and

hat starts out as to cells becomes one (called a zygote)


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0s the zygote travels don the fallopian tube toardsthe uterus it begins a series of cell divisions:

200- (e!ese Winslow, .S. *o/t. as ce!tain !igts


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n day , the zygote has divided into toidentical cells. 0t this stage it is called a ,cell

embryo.


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0nd then into four identical cells (also on day ,)


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1y day 3 each of those four cells has divided againmaking eight identical cells. %his is the early morula

(4berrylike5 shape).


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%he morula undergoes several more celldivisions (*6 3, 6+cells) and the individual

cells are no indistinct.


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n day 7 8uid builds up inside the ballof cells making it hollo. %his is the

blastocyst.

%he embryonic stem cells clump together inside the

blastocyst.

emb!yonic

stem cells

t!o'oblast


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91eteen days 6 and *+ implantation (theadhering of the blastocyst to the all of theuterus) occurs.

9 %he placenta also begins to form.90t this sta e there are no more embr onic

Wi1ime&ia ommons, 2007


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9 1eteen days *+ through ,* neurulation thebeginning of future nervous system takes place.9 1y day ,+ the beginnings of the future face neck

mouth and nose occur.

*!ay+s %natomy, -9-$ 3not te sow45 +


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9 rganogenesis or organ formation occursduring eeks 3 through -. %he primitive heartstarts beating at + eeks.9 1y eek - the developing embryo has

become a F;%eeks

Images by & tman, D


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•0t ,2 eeks the fetus is roughly ** incheslong and eighs about * lb *2 oz.•"t can suck its thumb yan and stretch.• %he mother can no feel it moving (called

4?uickening5).


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1irth

• 0 fullterm pregnancy lasts @ months or3- eeks.

• 0fter ,, eeks the fetus is considered

viable. %his means it could surviveoutside the uterus if there is a prematurebirth.

(omas Ha!twell, 2008

Unit 1 Natural Fertilization

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