Embryology Flashcards
Average fetal age
38 weeks from conception to birth
Gynecological age
Timing from LMP, usually about 40 weeks for gestational age.
Embryonic Period
First 8 weeks. All major organs formed.
Fetal period
Remaining 30 weeks. Organs grow larger and become more complex.
Zygote
The cell that forms when ova and sperm fuse.
Where does fertilization occur?
In the fallopian tube.
What is the zygote (morula)called when it enters the uterus?
Blastocyst
Inner cell mass forms?
The embryo
Trophoblast forms?
the placenta
When does implantation take place?
6 days post conception. Trophoblast erodes uterine wall. “Spotting” may occur.
Bilaminar embryonic disc
Gives rise to the whole body. Gives rise to trilaminar disc which forms the 3 layers.
What are the 3 layers?
Ectoderm, endoderm, mesoderm
Ectoderm and endoderm form?
epithelial tissues
Mesoderm forms?
Mesenchyme tissue. Tend to form muscle
When does the neural tube close?
begins at week 3, closes by week 4. folic acid is important for this.
Ectoderm
Forms epidermis, hair, nails and skin glands. Brian and spinal cord. Neural crest
Mesoderm
Vertebrae and ribs, Kidneys, gonads, connective tissue, heart, blood vessels, walls of digestive and resp tracts.
Endoderm
Epithelial lining and glands of digestive and respiratory tracts
When does the heart start pumping?
Around 1 month
During what period do most gross structural birth defects take place?
weeks 3-8. 3rd and 4th weeks are particularly vulnerable.
