**Question:** In ectopic pregnancy decidua is shed as:

A. endometrial glands
B. decidual cells
C. spiral arteries
D. zona radiata

**Core Concept:** Ectopic pregnancy is a type of pregnancy in which the fertilized egg implants outside the uterine cavity, most commonly in the fallopian tube. The decidua is a layer of cells that form part of the uterine lining during pregnancy, playing a crucial role in the establishment of pregnancy and maintenance of the uterine environment.

**Why the Correct Answer is Right:** In normal pregnancy, the decidua is shed during menstruation due to the coordinated actions of various hormones and enzymes. Decidual cells, primarily derived from the endometrial stromal cells, are responsible for the shedding of the decidua. These cells undergo apoptosis (programmed cell death) in response to the declining levels of progesterone and increasing levels of luteolytic hormones, like human chorionic gonadotropin (hCG) and luteinizing hormone (LH).

**Why Each Wrong Option is Incorrect:**

A. Endometrial glands are not involved in the shedding of decidua. They secrete various substances that aid in implantation and early pregnancy, but not in decidual shedding.

B. Decidual cells are not shed; instead, they undergo apoptosis, leading to shedding of the rest of the uterine lining (endometrium).

C. Spiral arteries are blood vessels that supply nutrients and oxygen to the endometrium, not involved in decidual shedding.

D. Zona radiata refers to the zona pellucida, a transparent zone surrounding the embryo after fertilization. It is not involved in decidual shedding.

**Clinical Pearl:** Understanding decidual shedding is crucial in diagnosing ectopic pregnancy, which can lead to life-threatening complications if left untreated. Clinical signs and symptoms for ectopic pregnancy include lower abdominal pain, vaginal bleeding, and elevated hCG levels. Immediate medical intervention is necessary to prevent maternal mortality.