Human placenta is derived from-

RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Obstetrics & Gynaecology

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Explanation

Chorion because the fetal part of the placenta originates from a specific region of the chorion.
This region, called the chorion frondosum, is characterized by the proliferation of chorionic villi, which are finger-like projections that invade the maternal uterine lining.
These villi establish the critical interface for nutrient, gas, and waste exchange between the mother and the fetus.
The other part of the chorion, the chorion laeve, becomes smooth as its villi degenerate.

Option A: The amnion is the innermost fetal membrane that forms the amniotic sac, which contains the fetus and amniotic fluid. It does not contribute to the formation of the placental tissue.
Option C: This is a close distractor. While the allantois gives rise to the umbilical blood vessels that vascularize the chorionic plate, the allantois itself does not form the structural tissue of the placenta. The placenta's tissue is derived from the chorion.
Option D: In humans, the allantois is a rudimentary (vestigial) structure. Its primary contribution is forming the umbilical arteries and vein, which are essential for connecting the fetus to the placenta, but it does not form the placenta itself.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Embryonic origin of the human placenta as background academic context rather than a clinical decision trigger.
Understanding the origin of the placenta is crucial for the prenatal diagnostic procedure known as Chorionic Villus Sampling (CVS). In CVS, a sample of chorionic villi is taken to test for genetic abnormalities in the fetus.
Abnormal development of the chorion can lead to placental insufficiency, a condition where the placenta cannot deliver enough oxygen and nutrients to the fetus, potentially causing intrauterine growth restriction (IUGR).
What if? If a patient has a placenta previa (where the placenta covers the cervix), knowledge of its chorionic origin helps the nurse understand the risk of severe bleeding, as the highly vascular chorionic tissue is in a vulnerable position.

How to Approach the Question

First, identify the core of the question: it asks for the tissue origin of the human placenta.
Recall the four main extraembryonic membranes: amnion, chorion, allantois, and yolk sac.
Systematically review the function of each membrane. The amnion forms the fluid-filled sac. The yolk sac is for early nutrition. The allantois is vestigial but forms umbilical vessels.
Focus on the chorion. Remember that it is the outermost membrane and develops villi that interact with the maternal uterus.
Differentiate between the structural origin of the placenta (chorion) and the origin of its blood supply (allantois). The question asks what it is 'derived from', implying the main tissue.
Conclude that the chorion is the correct source for the fetal part of the placenta.

Concept Tested & Keywords

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E6 Anatomy Grays 43e Vol 1 Part 2 pp. 9-11, 10-12