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We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Embryology: placental villi?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

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No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.

Embryology: placental villi MCQ (B11-ANAT2-32)

Q: What is the answer to this Anatomy question?

The best answer is D, Syncytiotrophoblast outermost; the cytotrophoblast beneath becomes discontinuous by term. The outer layer of a chorionic villus is the multinucleate syncytiotrophoblast, bathed by maternal blood in the intervillous space.

Q: What concept does this question test?

It tests Embryology: placental villi in Anatomy. The inner cytotrophoblast is a complete layer early, but becomes discontinuous late in pregnancy, which thins the placental barrier. The syncytiotrophoblast also produces hCG.

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Anatomy · Embryology: placental villi

Sample item

A pathologist examines placental villi from a first-trimester specimen and a term placenta by electron microscopy. In both, which layer forms the outermost covering of the villus in direct contact with maternal blood, and what happens to the layer beneath it?

AFetal endothelium outermost; the trophoblast beneath is lost by termBCytotrophoblast outermost; the syncytiotrophoblast beneath disappears by termCSyncytiotrophoblast outermost; the cytotrophoblast beneath becomes thicker by termDSyncytiotrophoblast outermost; the cytotrophoblast beneath becomes discontinuous by term

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Syncytiotrophoblast outermost; the cytotrophoblast beneath becomes discontinuous by term

The outer layer of a chorionic villus is the multinucleate syncytiotrophoblast, bathed by maternal blood in the intervillous space. The inner cytotrophoblast is a complete layer early, but becomes discontinuous late in pregnancy, which thins the placental barrier. The syncytiotrophoblast also produces hCG.

Option by option

A. Fetal endothelium outermost; the trophoblast beneath is lost by term
Fetal endothelium lies inside the villus core and is not in contact with maternal blood.
B. Cytotrophoblast outermost; the syncytiotrophoblast beneath disappears by term
The cytotrophoblast is the inner layer and does not form the outer covering.
C. Syncytiotrophoblast outermost; the cytotrophoblast beneath becomes thicker by term
The cytotrophoblast does not thicken; the barrier becomes thinner toward term.
D. Syncytiotrophoblast outermost; the cytotrophoblast beneath becomes discontinuous by term (correct)
Correct. The syncytiotrophoblast is outermost, and the cytotrophoblast thins out toward term.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Embryology: placental villi: practice question

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The answer and the reasoning

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