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Chapter VI

Prenatal and Infant Growth


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The normal process of prenatal and infant

growth is crucial to motor development of

the child. The lenght, weight, physique, and

maturational level of the child plays an

important role in his or her acquistion and

performance of rudimentary movement

patterns.


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Female Anatomy - Fertilization


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Fertilization and Implantation

Batshaw, M.L. et al (2007) Pg 24


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Prenatal Development: The Germinal

Stage

The one-celled zygotecreated at conceptiondivides by mitosis into 2genetically identical cellswithin 12 to 15 hours...and then another divisionto make 4 cells within thenext 12-15 hours... and soforth. By the third dayfollowing conception thecells have divided to form

a small ball that is knownas a morula. Themorula /blastocyst entersthe uterus and begins toimplant in the blood richlining of the uterus


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Embryo and Placental Formation

At one end of the blastocyst are cells that make upthe inner cell mass, which is destined to produce the

embryo

At the other end of the blastocyst is a mass of cells

that become the trophoblasts that progressively formthe placenta.


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Germinal Stage: Implantation

Implantation occurs when theblastocyst sinks into theendometrium.

Through the action ofhormones produced by theblastocyst, an intensivechemical exchange occursbetween the blastocyst and themother's tissue to signal itspresence in the uterus.

This exchange temporarilyimpairs the mother's immunesystem to prevent antibodiesfrom attacking the blastocystas foreign matter.


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Germinal Layers During the 2nd week after

conception, the inner cell

mass of the blastocyststructure separates into threedistinct layers

The outer layer or theectoderm ultimately forms the

skin, hair, sweat glands, theteeth, salivary glands, and thespinal cord (including thebrain). The middle layer, ormesoderm, will form themuscle, connective tissue,

bone, and blood vessels. The inner layer orendoderm,

will form most of the internalorgans (lungs, cardiac,digestive, and urinary

systems)


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Germinal Layers

These three layers are differentiated by the thirdweek following conception. They will continue toproliferate into the various organ system tissuesduring the embryonic period of prenatal

development.


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Embryonic Stage

From week three to week8 after ovulation and

fertilization

First trimester: Period of

prenatal development

when the most

permanent damage to

the embryo can take

place

Exposure to teratogenscan lead to structural

abnormalities and even

fetal death;

spontaneous abortionvs. no affect


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Prenatal Development: The Fetal Stage

Embryonic development: The primary organ

structures for all

internal/external structures

are present by the 15th day

after implantation

Fetal Stage: Months 3-9 Second & Third Trimesters


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During the childs first year there are rapid

gains in both weight and lenght.

Birth weight is doubled by the fifth month,

almost tripled by the end of the first year.

Length increasess to around 30 inches by

the first birthday.


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By age 2 boy have attained about 50

percent of their adult height and girls about

53 percent (Bayley, 1954)

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