Fetal Development

Lesson Objective

The student will explain the development of a fetus in the uterus.

Subobjective 1: The student will describe the different fetal development stages.

Subobjective 2: The student will determine how the embryo gets nourishment.

Subobjective 3: The student will explain how the mother and fetus affect each other's health.

Vocabulary Overview

List the stages of fetal development.

Describe the key events of each trimester during a pregnancy.

How does the fetus receive nutrients and oxygen from the mother?

Building Background

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Before T or F

After T or FStatement

The blastocyst implants into the uterus.

The amniotic sac is how the mother and fetus exchange nutrients and oxygen.

The umbilical cord contains arteries only, no veins.

The blood flow of the mother and fetus never mix but do flow past each other.

Human pregnancies are divided into 3 trimesters.

Zygote

• Cell that forms from a female egg being fertilized from a male sperm

• Diploid

• Chromosomes of mother combine with chromosomes of father

• Human zygote

Fill in each box with the relevant information for the given vocabulary word.

Frayer Model

Blastocyst

• A hallow ball of cells formed from the developing zygote

• The surface cells allow the blastocyst to implant into the uterine wall. • Small enough to fit inside the eye of Roosevelt on a dime

• Human blastocyst

Fill in each box with the relevant information for the given vocabulary word.

Frayer Model

Embryo

• A stage of fetal development when three cell layers begin to develop

• These three layers include the ectoderm, mesoderm, and the endoderm.

• Human embryo

Frayer Model

Placenta

• The organ that connects the mother to the fetus

• Allows for the exchange of wastes, nutrients, and oxygen

• Human placenta

Frayer Model

Fetus

• A stage of development from 9 weeks until birth

• Starting to take on appearance of the species

• Human Fetus

Fill in each box with the relevant information for the given vocabulary word.

Frayer Model

As it travels, it divides rapidly and transforms from a zygote to a blastocyst.

Once the egg is fertilized, it travels down the fallopian tubes to the uterus.

Fertilization

Occurs when the sperm enters the egg and their nuclei fuse.

As soon as one sperm enters the outer layer of the egg, a protective shield keeps any

more sperm from entering.

Click here to discover what happens when the egg is penetrated.

Implantation

The blastocyst implants into the uterine wall.

Pregnancy has now begun. The blastocyst

develops three cell layers.

BlastocystBlastocyst

1.

Ectoderm2.

Endoderm3.

Mesoderm

Once these layers form, the blastocyst is now referred to as an embryo.

Embryonic Membranes

There are many structures that protect and nourish the growing fetus. Placenta: the organ that connects the mother to the fetus

Umbilical Cord: consists of two arteries and a vein that transport oxygen. Other nutrients and waste also travel through the cord.

Amniotic Sac: a sac filled with amniotic fluid that cushions the fetus from temperature changes and sudden shock

1

2

3

The blood of the mother and fetus never mix to prevent the mother's body from rejecting the fetus and ending the pregnancy.

Do the mother's blood and the fetus's blood ever mix?

Trimesters

Human pregnancy is divided up into 3 trimesters that are about 13 weeks long.

Many hormones are involved in maintaining the pregnancy:

Estrogen Progesterone

Human Chorionic Gonadotropin

First Trimester

Embryonic stem cells differentiate into their future tissue or organ.

Embryos are more susceptible to genetic errors, chemicals, or anything harmful the mother may consume.

First Trimester

Weeks 1-9 Weeks 10-14

Click the images below to link to online video animations.

Second Trimester

The fetus continues to develop physically and mentally.

This results in increased movement that the mother can start to feel.

Second Trimester

Weeks 15-20 Weeks 21-27

Click the images below to link to online video animations.

Third Trimester

Fetus has now reached its largest size.

While most of the major organs and tissues are formed, the fetus is now focused on gaining weight.

Third Trimester

Weeks 28-38

Click the images below to link to online video animations.

Health of the Fetus

The fetus completely depends on the mother for all of its nutrients.

These nutrients include:

Toxic chemicals taken by the mother can interfere with the fetus's development and lead to disabilities and deformities in the child.

Health of the Mother

Just as the fetus is affected by the mother's intake, the mother is affected by the fetus.

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Review Questions

zygote.

placenta.

testes of the father.

ovaries of the mother.

A scientist wants to change the DNA of a sexually reproducing organism and have the new DNA present in every cell of the organism. In order to do this after fertilization, she would change the DNA in the ______.

Review Questions

Abnormalities present in the cells that line the uterus may prevent the production of offspring by directly interfering with the __________________.

Review Questions

The drinking of alcoholic beverages by a pregnant woman is harmful to the development of her fetus. This is most damaging early in a pregnancy because during this time ____________________.

Review Questions

Gestation for a human embryo ends when___________.

Review Questions

The embryo is protected from shock by a substance called _______________.

Wrap Up

Explain how nutrients and oxygen are transported between the mother and her fetus.