This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetus Placenta & Fetal Membrane, Subject name: Gynaecology & Obstetrics
Which of the trophoblast does not invade spiral arterioles:- 
Select and explain. 
A. Extravillous, B. Endovascular, C. Tertiary villus, D. Interstitial
D: Interstitial
Answer: D: Interstitial 
Explanation: Ans. (d) InterstitialRef: Williams Obstetrics 25th Ed; Page No-88* After implantation; trophoblast giving rise to villous and extra villous trophoblasts.* Extra villous trophoblasts contact with various maternal cell types because it migrate into the decidua and myometrium and also penetrate maternal vasculature.* Extra villous trophoblasts are found outside the villus and it is further subdivided into endovascular and interstitial trophoblasts. * Interstitial trophoblasts invade the decidua and surround spiral arteries.* Endovascular trophoblasts invade and transform spiral arteries during pregnancy to create low-resistance blood flow that is characteristic of the placenta.