The 3 Stages of
Prenatal Development
The Fetal Period...
8 Weeks
- Less than 2.54cm
- Face is forming with rudimentary eyes, ears, mouth and tooth buds
- Arms and legs moving
- Brain is forming
- Heartbeat is detectable with an ultrasound
- Called an "embryo"
- About 7.6cm, weighs 28g
- Can move arms, legs, fingers and toes
- Fingerprints are present
- Smile, frown, suck and swallow
- Sex
- Can urinate
- Called a "fetus"
- 25-30cm, weighs about 227-454g
- Heartbeat is audible with stethoscope
- Sucks thumb
- Hiccups
- Hair, eyelashes, eyebrows are present
- 36 to 43cm, weighs about 1,100 to 1,400g
- Adding body fat
- Very active
- Rudimentary breathing movements are present
36 to 40 Weeks
- 50cm, weighs about 3,200 grams
- Skin is less wrinkled
- Lanugo is mostly gone
- Less active
- Gaining immunities from mom
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
Amnion - A life support system that is like a bag or envelope containing a clear fluid in which the developing embryo floats
Placenta - A life support system that consists of a disc-shaped group of tissues in which small blood vessels from the mother and offspring intertwine but do not join
Umbilical cord- A life-support system containing two arteries and one vein that connects the baby to the placenta
Germinal Stage
- 28-36cm,weighs about 454-680 grams
-Skin is wrinkled and has protective coating
- Eyes are open
- Waste is collected in the bowel
- Has strong grip
12 Weeks
16 Weeks
20 Weeks
24 Weeks
28 Weeks
32 Weeks
- About 14cm, weighs about 112 grams
- Heartbeat is strong
- Skin is thin, transparent
- Downy hair covers body
- Fingernails and toenails forming
- Coordinated movements
- 42-46cm, weighs about 1,800 to 2,300 grams
- Has periods of sleep and wakefulness
- Responds to sounds
- May assume birth position
- Bones of head are soft and flexible
- Iron is being stored in the liver
Note:
Weeks 38-40 are known as the full term stage as due dates are set between these weeks
Weeks 41-45 are known as the postmature
Germinal Stage
3. The Fetal Stage:
from week 8 to birth
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.
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
Embryonic Stage
Blastomere
Embryonic Stage
- The blastocyst will attach to the uterine wall resulting in implantation.
Embryonic 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 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.
Embryonic Stage
- Implantation occurs when the blastocyst nestles into the uterine lining and ruptures tiny blood vessels that provide nutrients for the embryo and fetus until birth.
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 heart, spine and brain begins to form.
As a zygote enters the embryonic stage it does not yet possess human qualities and human features; however, it is still a human being...
Germinal Stage
Embryonic Stage
Tobacco use also poses a major threat to the embryo during the embryonic stage as it increases the risk of miscarriage.
If implantation is successful, hormonal changes stop the menstrual cycle from occurring and cause physical changes in the mother.
Embryonic Stage
- Researches estimate that 58% of all natural conceptions never become properly implanted and therefore the new life ends before the mother is even aware she is pregnant.
1. The Germinal Stage:
from conception to week 2
The embryo's arms, hands, fingers, legs, feet, toes, eyes and ears
After the two weeks of the germinal stage, the zygote moves onto the embryonic stage of its life.
begin to form, allowing the embryo to look human.
Embryonic Stage
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, eyes, teeth, palate, genitals, ears, upper and lower limbs are the most vulnerable to damage.
Embryonic Stage
Teratogens are any external agents that have the potential to harm an embryo.
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
Trophoblast - The outer layer of cells that develops in the germinal period. These cells later develop into the embryo
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.
Embryonic Stage
After the six weeks of the embryonic stage, the embryo moves onto the fetal stage of its life.
The Fetal Stage
During week 28:
The fetus has his/her own regular intervals for sleeping and being awake
The fetus can also open and close his/her eyes freely (may suck his/her thumb)
The feet are approximately 2 inches long and the hair is now visible
Eyes are able to rotate in sockets
Embryonic Stage
Fetal Alcohol Syndrome is a series of genetic problems associated with excessive alcohol use.
Excessive alcohol use may result in:
- microcephaly
- heart defects
- delayed mental development
- delayed motor development
Germinal 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.
2002 March
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
Beginning week 27:
The fetus weighs just over 2 pounds and is approximately 14 inches long
The eyes begin to open as the retina develops
The neural tube develops into the brain and spinal cord, and neurons form
Sadly, if the baby is born in week 27. the chance of survival is 80%.
Overview of the 3 Stages:
1. Germinal Stage
Conception - Week 2
2. Embryonic Stage
Week 2 - Week 8
3. Fetal Period
Week 8 - Birth
Jessie and Rebecca