This book was prepared to present an integrated review of selected topics in Human Embryology. It is designed specifically for students who completed stan dard courses in the various anatomical disciplines and who wish to review the developmental history of the major organ systems. This book will provide medical students with a highly suitable review for Step 1 of the United States Medical Licensing Exam (USMLE, Step 1). R. E. Coalson J. J. Tomasek Acknowledgments We wish to acknowledge the invaluable assistance provided by our colleagues at the University of Oklahoma Health Sciences Center during preparation of this review. In particular, we would like to thank Ms. Nancy Halliday for proofread ing, Mr. Shawn Schlinke for preparation of the illustrations, Mr. Melville Vaughan for assistance with mounting the illustrations, and Ms. Trenda Tanner for assis tance with the typing. Contents Preface to the Oklahoma Notes. v Preface. vii Acknowledgments. viii 1. Gametogenesis. 1 2. Female Reproductive Cycle. 9 3. Fertilization and Pregnancy. 12 4. Implantation and Formation of the Deciduae. 15 5. Formation of the Placenta. 18 6. Fetal Membranes and Umbilical Cord. 22 7. Early Development of the Conceptus 26 8. Development of General Body Form. 32 9. Nervous System. 35 10. Musculoskeletal System.:. 46 11. Integumentary System. 57 12. Oral Cavity and Development of the Branchial Apparatus. 62 13. Differentiation of the Branchial Apparatus. 66 14. Face and Palate. 72 15. Digestive System and Mesenteries. 78 16. Diaphragm and Body Cavities. 86 17. Respiratory System.