Trophoblasts form the?

Appeared in: DSSSB - 29 August 2019 (Shift-1)

Explanation

Trophoblasts are the cells forming the outer layer of a blastocyst, which provides nutrients to the embryo and develops into a large part of the placenta.
Following fertilization, the blastocyst implants into the uterine wall. The trophoblast cells are responsible for this invasion.
The trophoblast proliferates and differentiates into the cytotrophoblast and syncytiotrophoblast, which together form the chorionic villi.
These chorionic villi are the functional units of the placenta, facilitating the exchange of nutrients, gases, and waste between the mother and the fetus.

Option A: The amnion is the membrane that encloses the embryo in a protective, fluid-filled sac.
Option B: The embryo proper develops from the inner cell mass (also called the embryoblast), which is the cluster of cells located inside the blastocyst.
Option D: The ovum is the mature female reproductive cell (egg) before it is fertilized by a sperm.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Embryonic development and derivatives of the blastocyst as background academic context rather than a clinical decision trigger.
The syncytiotrophoblast, a layer of the trophoblast, produces the hormone human chorionic gonadotropin (hCG). This is the hormone detected in urine and blood tests to confirm pregnancy.
Abnormal proliferation of trophoblastic tissue can lead to gestational trophoblastic disease (GTD), which includes conditions like hydatidiform mole (molar pregnancy) and the malignant choriocarcinoma.
Proper function of the trophoblast is crucial for a healthy pregnancy. Defective trophoblast invasion is associated with pregnancy complications like pre-eclampsia and fetal growth restriction.

How to Approach the Question

First, identify the key term in the question: 'Trophoblasts'.
Recall the process of early embryonic development, specifically the formation of the blastocyst from the zygote.
Remember that the blastocyst is composed of two main parts: an outer cell layer and an inner cell mass.
Associate the outer layer, the trophoblast, with its primary functions: implantation into the uterus and providing nourishment. This directly links it to the formation of the placenta.
Differentiate this from the inner cell mass, which forms the embryo itself and its immediate surrounding structures like the amnion.
Based on this understanding, select 'Placenta' as the structure formed by the trophoblasts and eliminate the other options.

Concept Tested & Keywords

Qm9ONGNJIUMb4xyeJqmjUb

E6 Obstetrics Williams p. 70-95

E6 Anatomy Grays 43e Vol 1 Part 2 p. 10-12

Practise the full DSSSB - 29 August 2019 (Shift-1)

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