Fetal Fetal DevelopmentDevelopment

38-40 38-40 weeksweeks

Patricia M. Dillon August 2002

Mitosis Vs. MeiosisMitosis Vs. Meiosis

O0genisis vs. SpermatogenisisO0genisis vs. SpermatogenisisMeiosis of each spermatocyte produces 4 haploid spermatids. This process takes over three

weeks to complete.

In contrast to males, egg production begins in the ovaries prior to birth

and by the time the fetus is 25 weeks old, all the oogonia have

been formed by mitosis. Hundreds of these diploid cells develop into

primary oocytes that go through the first meiotic division (Meiosis 1) and

then stop until puberty when the ovum undergoes the 2nd mitotic

division after fertilization.

Courtesy of Penn State Biology Department

2003

• Week 2 -Conception is the moment at which the sperm penetrates the ovum in the fallopian tube. Pregnancy is counted from the first day of a woman’s last period, therefore, at conception the unborn infant is already considered to be two weeks old (Paul E. Rockwell, M.D.)

Forty-six chromosomes

combine and pre-determine a

person's characteristics

(traits).

Courtesy of Westside Pregnancy Resource Center

Courtesy of Penn State Biology Department

2003

Once fertilized it is called a zygote, until it Once fertilized it is called a zygote, until it

reaches the uterus 3-4 days later.reaches the uterus 3-4 days later.

• At 32 hours old, it is about the size of the head of a pin

Courtesy of Westside Pregnancy Resource Center

Embryonic StageEmbryonic Stage

• the developing organism from about two weeks after fertilization to the end of the seventh or eight week

Week 3Week 3 - - Once in the uterus, the Once in the uterus, the developing embryo is called a developing embryo is called a blastocyst.blastocyst.

• It implants by burrowing beneath the surface of the upper uterus.

Courtesy: The National Human Gnome Research Institute

•The yolk sac , produces blood cells during the early weeks of life. The unborn child is only one-sixth of an inch long, but is rapidly developing. Courtesy: http://

www.bartleby.com/

Courtesy of Stanford Univ Sea Urchin Courtesy of Stanford Univ Sea Urchin Embryology and Paul Kulesa, Rockman Institute, Pasadena CA Embryology and Paul Kulesa, Rockman Institute, Pasadena CA

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The umbilical cord The umbilical cord is the baby's lifeline is the baby's lifeline

to the mother. to the mother. Nourishment is Nourishment is transferred from transferred from

the mother's blood, the mother's blood, through the through the

placenta, and into placenta, and into the umbilical cord the umbilical cord to the fetus. If the to the fetus. If the

mother ingests any mother ingests any toxic substances toxic substances

(teratogens), such (teratogens), such as drugs or alcohol as drugs or alcohol (especially during (especially during

the 1the 1stst trimester – 3 trimester – 3 months), the baby months), the baby receives them too.receives them too.Courtesy of http://www.babycenter.com

-The embryo may float freely in the uterus for about 48 hours before implanting. Upon

implantation, complex connections between the mother and embryo develop to form the

placenta. The embryo also produces hormones which stop the mother's

menstrual cycle. 1)The heart starts beating

2)Eyes start to develop3)The brain, spinal cord,

……and nervous system begin to develop.

4)Arms and legs begin to grow5)Blood flows in veins

Week 4

1 month embryo

Courtesy of Westside Pregnancy Resource Center

Week 5Week 5The Embryo is the size of a raisin by day 21. 1) The embryo's tiny heart has begun

beating. 2) The neural tube enlarges into three parts,

soon to become a very complex brain. 3) The placenta begins functioning. 4) The spine and spinal cord grows faster

than the rest of the body at this stage and give the appearance of a tail. This disappears as the child continues to grow.

Week 6 to 8 The embryo is about 1/5 of an inch in length.

1) A primitive heart is beating. 2) Head (mouth, ears, and nose), liver, and intestines begin

to take shape. 3) Pituitary gland forms 4) Skeleton is formed 5) Reflex responses have begun 6) Brain coordinates movements of muscles and organs 7) Penis forms on males

8) Brain waves can be recorded 9) Lips are sensitive to touch10) Ears may resemble a family pattern11) Has every organ present12) Is 1 1/8 inches long and weighs about 1 gram

Week 8 The unborn child, called a fetus at this

stage, is about half an inch long. The tiny person is protected by the amniotic sac, filled with fluid. Inside, the child swims and moves gracefully.

1) The arms and legs have lengthened, and fingers can be seen. The toes will develop in the next few days.

2) Brain waves can be measured.

About 2 months

Week 10 to 12Week 10 to 12

1) Fingerprints start to form on fingers 2) Eyelids (close), palms, and hands are sensitive to touch. 3) Child will bend fingers around in the palm. 4) Fingernails start to form and thumb sucking may occur. 5) Can make a fist, move thumbs, bend wrists. 6) Squints, swallows, and frowns. 7) Body is sensitive to touch. 8) Begins to urinate. -9) Sex organs are formed (by the 10th week). 10) Makes complex facial expressions and even smiles.11) Can kick, turn feet, curl and fan toes. 12) Vocal cords are complete (by 12 weeks) and may cry in utero. 13) Can turn head, open mouth, and press lips tightly together. 14) Practices breathing.15) The brain is fully formed (by 12th week) and the fetus feels pain.

The embryo is now about 1 inch in length and very much The embryo is now about 1 inch in length and very much resembles a newborn baby.resembles a newborn baby. Facial features, limbs, hands feet Facial features, limbs, hands feet

fingers and toes become apparent. The nervous system is fingers and toes become apparent. The nervous system is responsive and many of the internal organs begin to function responsive and many of the internal organs begin to function

and twenty tiny deciduous (baby teeth) are forming in the and twenty tiny deciduous (baby teeth) are forming in the gums.gums.

Week 14 to 16Week 14 to 16

1) Face becomes prettier and facial expressions are present3) Movements are graceful4) Reflexes are vigorous5) Taste buds are present (15 weeks)

6) Sex organs may be seen on sonogram. 7) By 16 weeks, five and a half inches in length

and only six ounces in weight, eyebrows, eyelashes and soft, fine hair appear (lanugo).

The fetus is now 3 inches long and weighs almost an ounce. The child's

spontaneous movements can be observed.

3 to 4 months

Week 18 to 24Week 18 to 24

1) The fetus can hear and recognize mother's voice. 2) Responds to high sound frequencies. 3) At 20 weeks, the mother can feel the baby kick

(quickening). 4) Though still small and fragile, the baby is

growing rapidly. 5) Sweat glands develop, and the external skin has

turned from transparent to opaque. 6) Sleeping habits appear, but a feeding and loud

noises may provoke activity.7) The tender skin is still protected by a cheesy looking substance called vernix which, nearly absent by birth.

The fetus is now about ½ lbs and 10 inches by 6 months.

5-6 months

Courtesy of Pennsylvania Basic Embryology Review Program

Courtesy of Pennsylvania Basic Embryology Review Program

5 to 6 months

Week 26 to 32Week 26 to 32

1) At 26 weeks the fetus can inhale, exhale and even cry.

2) Eyes have completely formed, and the tongue has developed taste buds.

3) Under intensive supportive medical care the fetus has a over a 50% chance of surviving outside the womb.

4) By 32 weeks, the fetus sleeps 90-95% of the day, and sometimes experiences REM sleep (dreaming).

5) Eye teeth are present, eyes look around and hands grip strongly

The fetus’ weight is about 1lb 6 oz and length is about 9 inches.

About 8 months

Courtesy of Pennsylvania Basic Embryology Review Program

Week 38 to 40Week 38 to 40 The end of the gestational period, the child is ready for the extra-uterine environment. Average

weight is about 7 to 8 lbs and 19 to 20 inches.

1)At 9 months child triggers labor and birth occurs.

2)The placenta will detach from the side of the uterus and the umbilical cord will cease working as the child takes his first breaths of air.

3)Neonatal breathing will trigger changes in the structure of the heart and bypass arteries which will force all blood to now travel through the lungs.

Full Term Neonate38-40 weeks

gestation

ReferencesReferences• Baby Center: What Your Baby Looks Like As An Embryo. (2003). Retrieved -----

----- August 3, 2003 from http://www.babycenter.com/general/3276.html• Introduction to Child Development , 6th ed., (text book) John ----- ----- ----- ---- ----- -----

Dworetzky, West Publishing Company, San Francisco, CA, 1996. • Nine Month Miracle (CD ROM software) , A.D.A.M. Software, Inc., • -----1600 RiverEdge Parkway, Suite 800, Atlanta, GA, 30328.• Nova: The Greatest Miracle . (2001 November). Retrieved August 3, 2003 from -----

----- http://www.pbs.org/wgbh/nova/miracle/• The First Nine Months of Life, (brochure) Focus on the Family, ----- --- ----- ----- -----

----- Colorado Springs, CO, 1995. • Pennsylvania Basic Embryology Review Program. (1997). Retrieved August 3,

----- -- 2003 from http://www.med.upenn.edu/meded/public/berp/• Psychology Today, (magazine) Fetal Psychology, Janet L. Hopson, ----- ----- ---

October 1998. • Westside Pregnancy Resource Center: Fetal Development. (2002, October 31). ----- -

Retrieved August 3, 2003 from http://www.w-cpc.org• When You were Formed in Secret, (handbook) Gary Bergel, Intercessors for -----

----- --America, 1988.