Title: The 3 Stages of Prenatal Development by Justine Bartlett
Headings: The 3 Stages of Prenatal Development
The 3 Stages of Prenatal Development
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The 3 Stages of
Prenatal Development
2. The Embryonic Stage:
from week 2 to week 8
Terms:
Embryo- a human offspring in the early stages of development following conception
Differentiation- when cells multiply and begin to take on specific functions
Microcephaly- when the embryo's head is smaller than average
Teratogens- any external agents that have the potential to harm an embryo
Fetal Alcohol Syndrome- a series of genetic problems associated with excessive alcohol use
Embryonic Stage
Germinal Stage
If an abnormal event were to occur during the embryonic stage, the results would be devastating to the embryo and the mother, as several birth defects may occur...
The Fetal Stage: Maternal Illness and Exposure to Toxins
FACTS
Hazards: syphilis, cholera, smallpox, mumps, & severe cases of the flu.
3. The Fetal Stage:
from week 9 to week 38
Germinal Stage
Cell division can begin approximately 24-36 hours after conception.
The zygote divides and cells multiply at a rapid rate; 2, 4, 8, 16, etc and becomes a blastocyst.
When the cells divide into 8, they begin to distinguish what type of cells they will become.
As they continue to multiply, the outer cells become the protecting placenta and the inner cells form the embryo.
Weeks 38-40 are known as the full term stage;
due dates are set between these weeks
Weeks 41 and up, are known as the postmature (babies born after their due dates)
Blastocysts have 3 components:
1. The Ectoderm - will form skin and nails
2. The Endoderm - will form the digestive and respiratory tracts
3. The Mesoderm - will form the muscle and skeletal system
Cell Division
Blasdtomere
The Fetal Stage
Embryonic Stage
Weeks 12-19:
Fetus weighs approx. 14 grams & mother can now feel movement
Ability to smile & frown (via: muscle development)
Circulatory system is fully functioning & heart beat is strong
Neurons are multiplying rapidly & synapses are forming
Embryonic Stage
The embryonic stage occurs when the embryo's bodily systems and vital organs begin to form.
Cell division and movement are the basic processes that take place during this stage of development.
Tobacco use also poses a major threat to the embryo during the embryonic stage as it increases the risk of miscarriage. The risk of miscarriage is already quite high during this stage, which is another reason why it is known as the most vulnerable stage of pregnancy.
Embryonic Stage
As a zygote enters the embryonic stage it does not yet possess human qualities and human features
The cells of the embryo multiply and begin to take on specific functions. This process if know as differentiation. During this process, the embryo's
Germinal Stage
heart, spine and brain begins to form.
If implantation is successful, hormonal changes stop the menstrual cycle from occurring and cause physical changes in the mother.
Embryonic Stage
The embryo's arms, hands, fingers, legs, feet, toes, eyes and ears
1. The Germinal Stage:
from conception to week 2
The Fetal Stage
begin to form, allowing the embryo to look human.
The embryonic stage is known as the most vulnerable stage as all of the embryo's structures begin to form.
During the embryonic stage, the embryo's central nervous system, heart, teeth, palate, genitals, upper and lower limbs are the most vulnerable to damage.
Embryonic Stage
The step that marks the beginning of the germinal stage is the moment the sperm and egg fuse in the fallopian tube. This is known as conception.
After the egg is fertilized by the sperm, it becomes known as a zygote and moves through the fallopian tube to the uterus. This process can take a couple of hours or as long as a week.
Weeks 28-35:
Body fat is deposited for insulation
Respiratory & digestive systems mature
Fetus has his or her own regular intervals of sleeping & wakefulness
Embryonic Stage
After the two weeks of the germinal stage, the zygote moves onto the embryonic stage of its life.
Weeks 9-11:
Fetus weighs approximately 2 grams
Differentiation of ovaries & testes
Inner workings of ears develop
Neural tube develops into the brain
Spinal cord, & neurons form
Embryonic Stage
Terms:
Conception - when the sperm and egg touch in the fallopian tube
Fertilized egg - known as a zygote
Blastocyst - a cluster of rapidly growing cells
Implantation - when the blastocyst nestles into the uterine wall
The Fetal Stage
Week 29 & 30:
Muscles begin to mature
Bones begin to strengthen (noticeable due to their kicks & jabs)
Bones appear bright white on the sonogram
Facial features (i.e. nose) become well-defined
After the six weeks of the embryonic stage, the embryo moves onto the fetal stage of its life.
Embryonic Stage
The Fetal Stage
Fetal Alcohol Syndrome is a series of genetic problems associated with excessive alcohol use.
Teratogens are any external agents that have the potential to harm an embryo.
Excessive alcohol use may result in:
- microcephaly
- heart defects
- delayed mental development
- delayed motor development
Germinal Stage
Due to the fact that the embryo is attached to its mother via the placenta, a mother must be mindful of what she eats, the drugs she is taking, and her physical health as all of these teratogens pose a threat to the embryo's development.
Weeks 20-27:
Hair begins to grow
Visual & auditory senses become functional
Eyes can open freely
2002 March
The Fetal Stage
Check your Understanding
The Fetal Stage
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Weeks 36-38 (full term):
END OF PRENATAL DEVELOPMENT
Rapid increase in weight (approx. 6-7 lbs now)
Gains immunity from mother
Organ systems are fully developed &
functioning (lungs are last to mature)
Fetus is ready for birth at any day
Check your Understanding
Name the three stages of prenatal development in the order they occur.
Check your Understanding
Birth!!!
Name some of the teratogens that affect embryonic development?
Check your Understanding
What are the three stages of prenatal development?
Check your Understanding
What is the "baby" referred to in the Germinal stage?
What is the "baby" referred to in the Embryonic stage?
What is the "baby" referred to in the Fetal stage?
Overview of the 3 Stages:
1. Germinal Stage
Conception - Week 2
2. Embryonic Stage
Week 2 - Week 8
3. Fetal Period
Week 8 - Birth
Amanda, Justine and Liz

Content: due dates are set between these weeks
Weeks 41 and up, are known as the postmature (babies born after their due dates)
Blastocysts have 3 components: 1. The Ectoderm - will form skin and nails
2. The Endoderm - will form the digestive and respiratory tracts
3. The Mesoderm - will form the muscle and skeletal system
Cell Division
Blasdtomere
The Fetal Stage
Embryonic Stage
Weeks 12-19: Fetus weighs approx. 14 grams & mother can now feel movement
Ability to smile & frown (via: muscle development)
Circulatory system is fully functioning & heart beat is strong
Neurons are multiplying rapidly & synapses are forming
The blastocyst will attach to the uterine wall resulting in implantation. Embryonic Stage
The embryonic stage occurs when the embryo's bodily systems and vital organs begin to form. Cell division and movement are the basic processes that take place during this stage of development.