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
[{'content': 'Placenta develops from: \nSelect and explain. \nA. Chorion frondosum and decidua basalis, B. Chorion villi and decidua basalis, C. Chorion frondosum and decidua capsularis, D. Chorion villi and decidua parietalis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Chorion frondosum and decidua basalis1. The human placenta is of chorioallantoic type, consisting of 2 components:a. The chorion, or outer layers of the chorionic cavity, including:i. The syncytiotrophoblastii. The cytotrophoblastiii. The extraembryonic mesodermb. The allantois, containing the umbilical vessels and 3 foetal blood vessels: 2 arteries and 1 vein.2. The foetal trophoblast invades the endometrium, breaks down the endometrial blood vessels into lacunae, and forms villi around them.3. Thus, the placenta is a materno-foetal unit, with:i. The foetal portion formed by the chorion (chorionic plate)ii. The maternal portion formed by the decidua basalis (basal plate).4. The foeto-maternal interface consists of these opposed layers:i. The chorion frondosumii. Fibriniii. The decidua basalis', 'role': 'assistant'}]