Book updated May 2021. Now with 110+ questions. This book covers certain knowledge areas of the Step 1 component of the United States Medical Licensing Examination USMLE exam, which is often taken by medical students and graduates who seek to practice medicine in the US. This particular quick review module covers the Immune System, the Musculoskeletal System, the Respiratory System and others. Along your exam preparation effort, it is a good idea to stop and review what was learned. Repetition is an important element of learning, and one way to achieve content repetition is through quick review questions. It is important that these review questions are written to give learners a way to remember what they have learned, and to get them motivated. We create these quick review test questions referencing the concepts and principles currently valid in the exam. Answers to the review questions were defined through referencing certain web resources and medical text books.