Embryonic / Fetal Development Flashcards
When is the pre-embryonic period (zygote)?
Fertilization –> 2 weeks
When is the embryonic period (embryo)?
3 - 8 weeks
During the embryonic period, there is a high risk for ______
Teratogens - due to unknown pregnancy
When is the fetal period (fetus)?
9 weeks –> birth
What is a zygote?
A fertilized ovum
When is sex determined?
At the moment of fertilization
Describe the difference in speed between male / female sperm (2)
- Male sperm = faster
- Female sperm = slower
Where does fertilization take place?
The ampulla (outer third of the fallopian tube)
During ovulation, high estrogen levels increase ______ within the fallopian tube
Peristalsis
How long does it take for the zygote to move through the fallopian tube and reach the uterus?
3 days
What is a blastocyst?
Inner layer of cells that implants in the uterus
Where does the blastocyst implant?
Upper posterior part of the uterine wall
What does the blastocyst develop into? (2)
- Embryo
- Amnion
What is a trophoblast?
Outer layer of cells
What does the trophoblast develop into?
Chorion
What are the functions of chorionic villi? (2)
- Obtain oxygen / nutrients from maternal bloodstream
- Dispose of carbon dioxide / waste products
What hormone is secreted by chorionic villi?
hCG - detected in maternal serum 8 - 10 days after conception (basis for pregnancy tests)
What does the amnion eventually become?
The covering of the umbilical cord
The amnion and chorion together form the ______
Amniotic sac
What is the function of the yolk sac?
Aids in transferring maternal nutrients and oxygen
What are the primary germ layers? (3)
- Ectoderm
- Mesoderm
- Endoderm
Describe the embryonic phase (3)
- Tissues differentiate into essential organs
- Main external features develop
- Embryo is most vulnerable to teratogens
By 8 weeks, the crown-rump length is about ______ cm
3
What factors influence fetal development? (3)
- Genetic code
- Quality of sperm / egg
- Uterine environment - cells may die causing spontaneous abortion
