Exposure to toxins is particularly dangerous to the embryo in the first trimester of pregnancy because
A) its high surface-to-volume ratio provides a great deal of exposure to the toxin.
B) rapid cell division is taking place during this period.
C) tissue differentiation is occurring at its highest levels during this period.
D) branching sequences of developmental pathways are in their early stages in this period.
E) b, c, and d

Question

Quizplus · Accepted Answer

During the first trimester of pregnancy, the embryo is highly vulnerable to the harmful effects of toxins due to various reasons. Firstly, the embryo has a high surface-to-volume ratio, which enhances its exposure to toxic substances. Secondly, this period is characterized by rapid cell division, where the cells are actively replicating, differentiating and organizing themselves into various organs and tissues. Any disruption in this process can result in severe congenital defects or embryonic death. Thirdly, tissue differentiation is at its highest levels, and the organs are developing their unique functions and structures. Finally, the branching sequences of developmental pathways, which are critical to the embryo's viability, are in their early stages in this period. Therefore, any exposure to toxins can interfere with these pathways and lead to adverse effects on the embryo's development.

Exposure to Toxins Is Particularly Dangerous to the Embryo in the First