Question:medium
Cytotrophoblast invades which structure?
Cytotrophoblast invades which structure?
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Cytotrophoblast columns pass through the syncytiotrophoblast to reach the decidua basalis under the embryo.
Updated On: Jun 24, 2026
- Decidua parietalis
- Decidua basalis
- Decidua capsularis
- None
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Picture implantation: the conceptus burrows into the endometrium, and the surrounding endometrium is renamed decidua. The decidua is regionalised into basalis (beneath the embryo), capsularis (the cap over it), and parietalis (the rest of the lining).
Step 2: The trophoblast splits into two populations. The outer multinucleated syncytiotrophoblast leads the assault on the uterine epithelium, while the inner mononuclear cytotrophoblast acts as a stem-cell reserve that later extends columns through the syncytium.
Step 3: These cytotrophoblastic cell columns penetrate the syncytiotrophoblast and advance into the decidua lying directly under the embryo - that is the decidua basalis, which ultimately contributes to the maternal placenta.
Step 4: The capsularis and parietalis are not the targets of this deep invasion, and None is therefore incorrect. The cytotrophoblast invades the decidua basalis.
\[\boxed{\text{Decidua basalis}}\]
Step 2: The trophoblast splits into two populations. The outer multinucleated syncytiotrophoblast leads the assault on the uterine epithelium, while the inner mononuclear cytotrophoblast acts as a stem-cell reserve that later extends columns through the syncytium.
Step 3: These cytotrophoblastic cell columns penetrate the syncytiotrophoblast and advance into the decidua lying directly under the embryo - that is the decidua basalis, which ultimately contributes to the maternal placenta.
Step 4: The capsularis and parietalis are not the targets of this deep invasion, and None is therefore incorrect. The cytotrophoblast invades the decidua basalis.
\[\boxed{\text{Decidua basalis}}\]
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