embryology- 1 Flashcards
What is embryology?
the study of embryos and their development
What is gestation?
period of time required for full development of a fetus in utero
40 weeks 10 months
What is the first two weeks of gestation called?
pre-embryonic stage
What is a developing human during weeks 3-8 called?
embryo
What is a developing human called at week nine of gestation until birth?
fetus
What characterizes the pre-embryonic and embryonic stages?
- cell divison
- migration
- differentiation
What week are all the organ systems structured?
week 9
What occurs during weeks 1-2 of gestation?
- cellular division
- migration
- differentiation
- gastrulation
Initital cellular divisions in order?
- unfertilized oocyte
- fertilized oocuyre
- two cell stage
- 4 cell stage
- 8 cell stage
- morula (16 cells)
- blastocyte
- embryo hatches (sheds zona pellucidia)
- blastocyst rotates and implants into endometrium of the uterus
By the first week cavity forms and its now called?
blastocoel
What is an ectopic pregnancy?
occurs when a fertilized egg implants and grows outside of main cavity of uterus
Explain gastrulation
- In 3rd week of embryonic development specialized cells called epiblast and hypoblast undergo gastrulation.
- two cell layers become 3 germ layers and bodily axes observed in the mature adult are created
- cells of epiblast later break off
- migrate toward primitive streak
- detach and penetrate through epiblast layer to form 3 new layers (middle mesodermal layer, endodermal, ectoderm)
What is the middle mesodermal layer made from?
cells differentiate at primitive streak to form middle mesoderm layer (epiblast)
What cells form endodermal layer?
hypoclast cells
What cells form ectoderm layer?
epiblast
