The Period of the Embryo (~2 to 8 Weeks) Flashcards
(9 cards)
When does the embryonic period begin?
After the blastocyst implants in the uterine wall.
What does the inner layer of the blastocyst become?
The embryo.
What does the outer layer form?
Protective tissues.
What is gastrulation?
The formation of a longitudinal axis and cell migration to establish body structure.
What three layers of cells form during the embryonic period?
Mesoderm: Muscles, bones, circulatory and reproductive systems
Endoderm: Digestive and respiratory systems
Ectoderm: Skin and neural system (including the brain)
What major structures form from the connection between the blastocyst and uterus?
The placenta, umbilical cord, and amniotic sac.
What is special about the human placenta?
It’s more complex than in other species; forms a special ontogenetic niche.
How much larger is the embryo than the zygote at one month?
About 10,000 times larger.
By the end of the embryonic period, what is the developmental status of structures?
Virtually all major structures have formed or started forming.
