Flashcards in Early Embryology Deck (16)
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1
What does the embryo enter the uterine cavity as 3 days after fertilization?
Morula
2
What does the morula become by swelling with fluid?
Blastocyst--> formed in the 1st week; called blastocyst when it forms an inner cell mass
3
*What two structures compose the blastocyst?
1. Embryoblast (forms embyro)
2. Trophoblast (forms placenta)
4
What two structures develop from the trophoblast? When?
1. Cytotrophoblast
2. Syncytiotrophoblast
*in the 2nd week
5
What does the cytotrophoblast form?
Primary villi
6
What does the syncytiotrophoblast do?
Implants into the uterine wall and actually produces hCG--> is the outer portion of the trophoblast
7
In the second week, what two layers comprise the embryo?
Epiblast and hypoblast (called bilaminar disk)--> is composed of two germ layers at this point
8
What germ layer does the epiblast give rise to?
ectoderm
9
What structure does mesoderm and endoderm derive from?
primitive streak
10
What two cavities are present in the second week?
1. amniotic cavity
2. yolk sac
11
*Rule of 2's (3 rules)
In the 2nd week:
- 2 germ layers (bilaminar disc; epiblast, hypoblast)
- 2 cavities (amniotic cavity, yolk sac)
- 2 components to placenta (syncytio- and cytotrophoblast)
12
Rule of 3's (1 rule)
3 germ layers in the third week (endoderm, ectoderm, mesoderm)--> process of obtaining the three layers is called gastrulation; cells called gastrula in the 3rd week
13
What week does neural tube form and close?
4th week
14
What weeks does organogenesis take place?
Weeks 3-8; called embryonic period
15
When does implantation occur?
By the 7th day
16
