Fourth Edition provides a concise, focused review of the most important embryology information needed for the USMLE Step 1. Chapters cover prefertilization events and the embryonic period, embryologic development of each organ system, chromosomal abnormalities, inherited diseases, teratology and more. To prepare students for the clinical vignettes on the USMLE, the book includes numerous clinical cases with words and phrases that patients use. A mini-atlas at the end of each chapter presents photographs, MRIs, CT scans, and radiographs of various congenital malformations.