Langman’s Medical Embryology 14th Edition

Book Preface

Every student will be affected bypregnancy, either their mother’s, because what happens in the womb does not necessarily stay in the womb, or by someone else’s. As health care professionals, you will often encounter women ofchildbearing age who may be pregnant, or you may have children ofyour own, or maybe it is a friend who is pregnant. In any case, pregnancy and childbirth are relevant to all ofus, and unfortunately, these processes often culminate in negative outcomes. For example, 50% of all embryos are spontaneously aborted.

Furthermore, prematurity and birth defects are the leading causes ofinfant mortality and major contributors to disabilities. Fortunately, new strategies can improve pregnancy outcomes, and health care professionals have a major role to play in implementing these initiatives. However, a basic knowledge ofembryology is essential to the success ofthese strategies, and with this knowledge, every health care professional can play a role in providing healthier babies.

To accomplish its goal ofproviding a basic understanding ofembryology and its clinical relevance, Langman’s Medical Embryology retains its unique approach ofcombining an economy oftext with excellent diagrams and clinical images. It stresses the clinical importance ofthe subject by providing numerous clinical examples that result from abnormal embryological events. The following pedagogic features and updates in the 14th edition help facilitate student learning.

Organization ofMaterial: Langman’s Medical Embryology is organized into two parts. llqe first provides an overview ofearly development from gametogenesis through the embryonic period. Also included in this section are chapters on placental and fetal development as well as prenatal diagnosis and birth defects. llqe second part ofthe text provides a description ofthe fundamental processes ofembryogenesis for each organ system. Clinical Correlates: In addition to describing normal events, each chapter contains clinical correlates that appear in highlighted boxes.

This material is designed to demonstrate the clinical relevance ofembryology and the importance ofunderstanding key developmental events as a first step to improving birth outcomes and having healthier babies. Clinical pictures and case descriptions are used to provide this information, and this material has been increased and updated in this edition. Genetics: Because ofthe increasingly important role ofgenetics and molecular biology in embryology and the study ofbirth defects, basic genetic and molecular principles are discussed. llqe first chapter provides an introduction to molecular processes, defines terms commonly used in genetics and molecular biology, and describes key pathways used in embryonic development.

Then, throughout the text, major signaling pathways and genes that regulate embryological development are identified and discussed. Extensive Art Program: The artwork has always been designed to enhance understanding ofthe text and includes four-color line drawings, scanning electron micrographs, and clinical pictures. Once again, artwork has been added, especially to Chapter 18, to illustrate new concepts in development ofthe central nervous system, diaphragm, ear, and other structures. Summary: At the end ofeach chapter is a summary that serves as a concise review ofthe key points described in detail throughout the chapter. Key terms are highlighted and defined in these summaries.

Problems to Solve: Problems related to the key elements ofeach chapter are provided to assist the students in assessing their understanding ofthe material. Detailed answers are provided in an appendix at the back ofthe book. Glossary: A glossary ofkey terms has been expanded and is located in the back ofthe book. thePoint Web site: This site for students and instructors provides an interactive question bank ofUSMLE board-type questions. Teaching aids for instructors are also provided in the form ofan image bank and a series oflectures on the major topics in embryology presented in PowerPoint with accompanying notes.

I hope you find this edition ofLangman’s Medical Embryology to be an excellent resource for learning embryology and its clinical significance. Together, the textbook and online site, thePoint, are designed to provide a user-friendly and innovative approach to understanding the subject.
T.W. Sadler Sheridan, MT

I CLINICAL RELEVANCE

From a single cell to a baby in 9 months—a developmental process that represents an amazing integration ofincreasingly complex phenomena. The study ofthese phenomena is called embryology, and the field includes investigations ofthe molecular, cellular, and structural factors contributing to the formation ofan organism. These studies are important because they provide knowledge essential for creating health care strategies for better reproductive outcomes. Thus, our increasingly greater understanding ofembryology has resulted in new techniques for prenatal diagnoses and treatments; therapeutic procedures to circumvent problems with infertility; and mechanisms to prevent birth defects, the leading cause ofinfant mortality. These improvements in prenatal and reproductive health care are significant not only for their contributions to improved birth outcomes but also for their long-term effects postnatally. For example, both our cognitive capacity and our behavioral characteristics are affected by our prenatal experiences, and factors such as maternal smoking, nutrition, stress, diabetes, etc., play a role in our postnatal health. Furthermore, prenatal experiences, in combination with molecular and cellular factors, determine our potential to develop certain adult diseases, such as cancer and cardiovascular disease. Thus, our prenatal development produces many ramifications affecting our health for both the short and long term, making the study ofembryology and fetal development an important topic for all health care professionals. Also, with the exception ofa few specialties, most physicians and health care workers will have an opportunity to interact with women ofchildbearing age, creating the potential for these providers to have a major impact on the outcome ofdevelopmental processes and their sequelae.

I A BRIEF HISTORY OF EMBRYOLOGY

The process ofprogressing from a single cell through the period ofestablishing organ primordia (the first 8 weeks ofhuman development) is called the period of embryogenesis (sometimes called the period oforganogenesis); the period from that point on until birth is called the fetal period, a time when differentiation continues while the fetus grows and gains weight. Scientific approaches to study embryology have progressed over hundreds ofyears. Not surprisingly, anatomical approaches dominated early investigations. Observations were made, and these became more sophisticated with advances in optical equipment and dissection techniques. Comparative and evolutionary studies were part ofthis equation as scientists made comparisons among species and so began to understand the I CLINICAL RELEVANCE

From a single cell to a baby in 9 months—a developmental process that represents an amazing integration ofincreasingly complex phenomena. The study ofthese phenomena is called embryology, and the field includes investigations ofthe molecular, cellular, and structural factors contributing to the formation ofan organism. These studies are important because they provide knowledge essential for creating health care strategies for better reproductive outcomes. Thus, our increasingly greater understanding ofembryology has resulted in new techniques for prenatal diagnoses and treatments; therapeutic procedures to circumvent problems with infertility; and mechanisms to prevent birth defects, the leading cause ofinfant mortality. These improvements in prenatal and reproductive health care are significant not only for their contributions to improved birth outcomes but also for their long-term effects postnatally. For example, both our cognitive capacity and our behavioral characteristics are affected by our prenatal experiences, and factors such as maternal smoking, nutrition, stress, diabetes, etc., play a role in our postnatal health. Furthermore, prenatal experiences, in combination with molecular and cellular factors, determine our potential to develop certain adult diseases, such as cancer and cardiovascular disease. Thus, our prenatal development produces many ramifications affecting our health for both the short and long term, making the study ofembryology and fetal development an important topic for all health care professionals. Also, with the exception ofa few specialties, most physicians and health care workers will have an opportunity to interact with women ofchildbearing age, creating the potential for these providers to have a major impact on the outcome ofdevelopmental processes and their sequelae.

I A BRIEF HISTORY OF EMBRYOLOGY

The process ofprogressing from a single cell through the period ofestablishing organ primordia (the first 8 weeks ofhuman development) is called the period of embryogenesis (sometimes called the period oforganogenesis); the period from that point on until birth is called the fetal period, a time when differentiation continues while the fetus grows and gains weight. Scientific approaches to study embryology have progressed over hundreds ofyears. Not surprisingly, anatomical approaches dominated early investigations. Observations were made, and these became more sophisticated with advances in optical equipment and dissection techniques. Comparative and evolutionary studies were part ofthis equation as scientists made comparisons among species and so began to understand the