Book excerpt: Master the concepts you need to know with Human Embryology and Developmental Biology. Dr. Bruce M. Carlson's clear explanations provide an easy-to-follow "road map" through the most up-to-date scientific knowledge, giving you a deeper understanding of the key information you need to know for your courses, exams, and ultimately clinical practice. Visualize normal and abnormal development with hundreds of superb clinical photos and embryological drawings. Access the fully searchable text online, view animations, answer self-assessment questions, and much more at www.studentconsult.com. Grasp the molecular basis of embryology, including the processes of branching and folding - essential knowledge for determining the root of many abnormalities. Understand the clinical manifestations of developmental abnormalities with clinical vignettes and Clinical Correlations boxes throughout. Your purchase entitles you to access the web site until the next edition is published, or until the current edition is no longer offered for sale by Elsevier, whichever occurs first. If the next edition is published less than one year after your purchase, you will be entitled to online access for one year from your date of purchase. Elsevier reserves the right to offer a suitable replacement product (such as a downloadable or CD-ROM-based electronic version) should access to the web site be discontinued.