The outer most membrane of placenta is called?

Appeared in: AIIMS Patna NO - 2020

Explanation

The chorion is the outermost fetal membrane that surrounds the embryo and the other membranes.
It develops from the trophoblast and is responsible for forming the fetal portion of the placenta.
The chorion is in direct contact with the maternal uterine lining (decidua), making it the most external of the fetal membranes.

Option A: The yolk sac is an early embryonic structure that provides initial nourishment. It regresses as the placenta develops and is located between the amnion and chorion, not as the outermost layer.
Option C: The amnion is the innermost fetal membrane that encloses the amniotic fluid and the fetus. The question asks for the outermost membrane.
Option D: Meningitis is the inflammation of the meninges, which are the membranes covering the brain and spinal cord. It is a pathological condition and not a part of placental anatomy.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy of the placenta and fetal membranes as background academic context rather than a clinical decision trigger.
Nurses and midwives inspect the placenta and membranes after delivery to ensure they are complete. Retained placental fragments, including parts of the chorion, can cause postpartum hemorrhage or infection.
The nature of the membranes (e.g., dichorionic vs. monochorionic) is crucial in managing twin pregnancies, as it affects the risk of complications like twin-to-twin transfusion syndrome.
What if? If a patient has a 'monochorionic-diamniotic' twin pregnancy, it means the twins share one outer chorion but have separate inner amnions. This is a higher-risk pregnancy requiring more frequent monitoring than a 'dichorionic-diamniotic' pregnancy where each twin has their own complete set of membranes.

How to Approach the Question

First, identify the key terms in the question: 'outer most membrane' and 'placenta'.
This is a direct recall question about the anatomy of pregnancy.
Consider each option: 'Amnion' and 'Chorion' are the two main fetal membranes. 'Yolk sac' is an early embryonic structure. 'Meningitis' is a disease process.
Eliminate the obviously incorrect option, 'Meningitis', as it is a neurological condition, not a placental structure.
Recall or deduce the relationship between the amnion and chorion. The chorion is the outer layer that interfaces with the uterus, while the amnion is the inner sac holding the fluid and fetus.
Select the option that correctly identifies the outermost membrane.

Concept Tested & Keywords

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

Practise the full AIIMS Patna NO - 2020

Attempt every question from this paper in a timed mock, then review the full solution for each one.