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Second Week Embryonic Development Highlights
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1
Question
What marks the beginning of the second week of embryonic development?
Page 1
Answer
Implantation of the blastocyst in the uterine endometrium
2
Question
What is the approximate size of the blastocyst at the start of implantation?
Page 2
Answer
0.2 mm
3
Question
What initiates during the second week of development?
Page 2
Answer
Differentiation of the first cellular layers
4
Question
What exchange begins in the second week?
Page 2
Answer
Nutrients between mother and embryo
5
Question
During which days post-ovulation does complete blastocyst implantation occur?
Page 3
Answer
Days 6-10
6
Question
What endometrial changes support implantation?
Page 3
Answer
Increased vascularization and edema
7
Question
What are the two layers the trophoblast differentiates into?
Page 3
Answer
Cytotrophoblast and syncytiotrophoblast
8
Question
How does the blastocyst position itself during complete implantation?
Page 3
Answer
Deeply embedded in endometrial tissue
9
Question
What is the primary function of the syncytiotrophoblast?
Page 4
Answer
Active invasion using proteolytic enzymes
10
Question
What structural feature defines the syncytiotrophoblast?
Page 4
Answer
Multinucleated mass from cell fusion
11
Question
How does the syncytiotrophoblast interact with maternal blood vessels?
Page 4
Answer
Penetrates them to access nutrients
12
Question
What spaces does the syncytiotrophoblast form?
Page 4
Answer
Placental lacunae filled with maternal blood
13
Question
What circulation begins due to syncytiotrophoblast activity?
Page 4
Answer
Uteroplacental circulation
14
Question
What hormone does the syncytiotrophoblast synthesize?
Page 4
Answer
hCG to maintain pregnancy
15
Question
What is the bilaminar germ disc?
Page 5
Answer
Flat structure from epiblast and hypoblast layers
16
Question
What cells compose the epiblast?
Page 5
Answer
Tall, columnar cells surrounding the amniotic cavity
17
Question
What does the epiblast give rise to?
Page 5
Answer
All proper embryonic structures and participates in gastrulation
18
Question
What cells make up the hypoblast?
Page 5
Answer
Cuboidal cells forming the roof of the primitive yolk sac
19
Question
What do hypoblast cells contribute to?
Page 5
Answer
Essential extraembryonic structures for early nutrition
20
Question
What is the amniotic cavity?
Page 6
Answer
Fluid-filled space surrounded by amnioblasts from epiblast
21
Question
What lines the primitive yolk sac?
Page 6
Answer
Hypoblast and exocoelomic membrane
22
Question
What is the chorionic cavity?
Page 6
Answer
Extraembryonic space between mesoderm and trophoblast surrounding the embryo
23
Question
How do the three embryonic cavities relate?
Page 6
Answer
They interrelate to form a functional trilaminar complex
24
Question
What are decidual cells in the endometrium?
Page 7
Answer
Cells accumulating lipids and glycogen around implantation site
25
Question
What facilitates syncytiotrophoblast invasion?
Page 7
Answer
Endometrial apoptosis (programmed cell death)
26
Question
What is the decidual reaction?
Page 7
Answer
Physiological transformation of endometrium for nutrition and immunoprotection
27
Question
Why is increased endometrial vascularization important?
Page 3
Answer
Supports nutrient delivery and edema for implantation
28
Question
How does cytotrophoblast differ from syncytiotrophoblast?
Page 3
Answer
Cytotrophoblast is cellular layer; syncytiotrophoblast is multinucleated invasive layer
29
Question
What role does hCG play in early pregnancy?
Page 4
Answer
Maintains corpus luteum to prevent menstruation
30
Question
Why is the bilaminar disc considered the base of embryonic development?
Page 5
Answer
It establishes the two primary germ layers for all future structures