The Developing Human Clinically Oriented Embryology Ninth Edition Keith L. Moore, MSc, PhD, FIAC, FRSM, FAAA Professor Emeritus, Division of Anatomy, Department of Surgery Faculty of Medicine, University of Toronto Former Professor and Head, Department of Anatomy, University of Manitoba, Winnipeg, Manitoba, Canada Former Professor and Chair, Department of Anatomy and Cell Biology, University of Toronto, Toronto, Ontario, Canada T.V.N. Persaud, MD, PhD, DSc, FRCPath (Lond.), FAAA Professor Emeritus and Former Head, Department of Human Anatomy and Cell Science, Professor of Pediatrics and Child Health, Associate Professor of Obstetrics, Gynecology, and Reproductive Sciences, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada Professor of Anatomy and Embryology, St. George’s University, Grenada, West Indies Mark G. Torchia, MSc, PhD Associate Professor and Director of Development, Department of Surgery, Associate Professor, Department of Human Anatomy and Cell Sciences, Director, University Teaching Services, University of Manitoba, Winnipeg, Manitoba, Canada Saunders Award Keith L. Moore Recipient of the inaugural Henry Gray/Elsevier Distinguished Educator Award in 2007—the American Association of Anatomists, highest award for excellence in human anatomy education at the medical/dental, graduate, and undergraduate levels of teaching; the Honored Member Award of the American Association of Clinical Anatomists (1994) for significant contributions to the field of clinically relevant anatomy; and the J.C.B. Grant Award of the Canadian Association of Anatomists (1984) “in recognition of meritorious service and outstanding scholarly accomplishments in the field of anatomical sciences.” In 2008 Professor Moore was inducted as a Fellow of the American Association of Anatomists. The rank of Fellow honors distinguished AAA members who have demonstrated excellence in science and in their overall contributions to the medical sciences. T.V.N. (Vid) Persaud Recipient of the Henry Gray/Elsevier Distinguished Educator Award in 2010—the American Association of Anatomists’ highest award for excellence in human anatomy education at the medical/dental, graduate, and undergraduate levels of teaching; the Honored Member Award of the American Association of Clinical Anatomists (2008) for significant contributions to the field of clinically relevant anatomy; and the J.C.B. Grant Award of the Canadian Association of Anatomists (1991) “in recognition of meritorious service and outstanding scholarly accomplishments in the field of anatomical sciences.” In 2010 Professor Persaud was inducted as a Fellow of the American Association of Anatomists. The rank of Fellow honors distinguished AAA members who have demonstrated excellence in science and in their overall contributions to the medical sciences. Front Matter The Developing Human Clinically Oriented Embryology 9th Edition Keith L. Moore, MSc, PhD, FIAC, FRSM, FAAA Professor Emeritus, Division of Anatomy, Department of Surgery Faculty of Medicine, University of Toronto, Former Professor and Head, Department of Anatomy, University of Manitoba, Winnipeg, Manitoba, Canada Former Professor and Chair, Department of Anatomy and Cell Biology, University of Toronto, Toronto, Ontario, Canada T.V.N. Persaud, MD, PhD, DSc, FRCPath (Lond.), FAAA Professor Emeritus and Former Head, Department of Human Anatomy and Cell Science Professor of Pediatrics and Child Health Associate Professor of Obstetrics, Gynecology, and Reproductive Sciences, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada Professor of Anatomy and Embryology, St. George’s University, Grenada, West Indies Mark G. Torchia, MSc, PhD Associate Professor and Director of Development, Department of Surgery Associate Professor, Department of Human Anatomy and Cell Sciences Director, University Teaching Services, University of Manitoba Winnipeg, Manitoba, Canada