This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Organogenesis is maximally affected in which period of gestation ? 
Select and explain. 
A. 1-4 weeks, B. 4-8 weeks, C. 10-15 weeks, D. 15-20 weeks
B: 4-8 weeks
Answer: B: 4-8 weeks 
Explanation: Ans. is 'b' i.e., 4-8 weeksThe development of a new individual in the uterus involves three phases :-Pre-embryo phase or germinal phase (day 0-3 weeks).Embryo phase or embryonic period (weeks 4-8).Fetal phase (weeks 8-38).The embryonic period of development extends from fouh to eighth week of gestation and is also called period of organogenesis.During this period the main organ systems are developed from three germinal layers. However, the function of most of them is negligible except for cardiovascular system, i.e. cardiovascular system is the earliest to function.