Langman Medical Embryology – Langman

A. The intraembryonic cavity is in open communication with the extraembryonic cavity. B. The intraembryonic cavity is about to lose contact with the extraembryonic cavity. C. At the end of the fourth week, splanchnic mesoderm layers are continuous with somatic layers as a double-layered membrane, the dorsal mesentery. Dorsal mesentery extends from the caudal limit of the foregut to the end of the hindgut. D and E. Scanning electron micrographs of sections through mouse embryos showing details similar to those in B and C, respectively.

G, Gut tube; arrowheads, splanchnic mesoderm; C, body cavity; arrow, dorsal mesentery; A, dorsal aorta; NT, neural tube. usually on the right, through a region weakened by regression of the right um- bilical vein, which normally disappears. Viscera are not covered by peritoneum or amnion, and the bowel may be damaged by exposure to amniotic fluid. Both omphalocele and gastroschisis result in elevated levels of α-fetoprotein in the amniotic fluid, which can be detected prenatally. Part Two: Special Embryology Heart Figure 10.3 Ventral body wall defects. A. Infant with ectopia cordis.

Mesoderm of the sternum has failed to fuse, and the heart lies outside of the body. B. Omphalocele with failure of the intestinal loops to return to the body cavity following physiological herniation. The herniated loops are covered by amnion. C. Omphalocele in a newborn. D. A newborn with gastroschisis. Loops of bowel return to the body cavity but herniate again through the body wall, usually to the right of the umbilicus in the region of the regressing right umbilical vein. Unlike omphalocele, the defect is not covered by amnion.

Chapter 10: Body Cavities Lung bud Pleuro- pericardial fold Phrenic nerve Common cardinal vein Heart Figure 10.4 A. Scanning electron micrograph showing the ventral view of a mouse embryo (equivalent to approximately the fourth week in human development). The gut tube is closing, the anterior and posterior intestinal portals are visible (arrowheads), and the heart (H) lies in the primitive pleuropericardial cavity (asterisks), which is partially separated from the abdominal cavity by the septum transversum (arrow).

B. Portion of an embryo at approximately 5 weeks with parts of the body wall and septum transversum removed to show the pericardioperitoneal canals. Note the size and thickness of the septum transversum and liver cords penetrating the septum. C.

The ninth edition of Langman’s Medical Embryology adheres to the tradition established by the original publication—it provides a concise but thorough de- scription of embryology and its clinical significance, an awareness of which is essential in the diagnosis and prevention of birth defects. Recent advances in ge- netics, developmental biology, maternal-fetal medicine, and public health have significantly increased our knowledge of embryology and its relevance. Because birth defects are the leading cause of infant mortality and a major contributor to disabilities, and because new prevention strategies have been developed, under- standing the principles of embryology is important for health care professionals.

To accomplish its goal, Langman’s Medical Embryology retains its unique ap- proach of combining an economy of text with excellent diagrams and scanning electron micrographs. It reinforces basic embryologic concepts by providing numerous clinical examples that result from abnormalities in developmental processes. The following pedagogic features and updates in the ninth edition help facilitate student learning: Organization of Material: Langman’s Medical Embryology is organized into two parts.

The first provides an overview of early development from gametogenesis through the embryonic period; also included in this section are chapters on placental and fetal development and prenatal diagnosis and birth defects. The second part of the text provides a description of the fundamental processes of embryogenesis for each organ system. Molecular Biology: New information is provided about the molecular basis of normal and abnormal development.

Extensive Art Program: This edition features almost 400 illustrations, includ- ing new 4-color line drawings, scanning electron micrographs, and ultrasound images. Clinical Correlates: In addition to describing normal events, each chapter con- tains clinical correlates that appear in highlighted boxes. This material is de- signed to provide information about birth defects and other clinical entities that are directly related to embryologic concepts.

vii viii Preface Summary: At the end of each chapter is a summary that serves as a concise review of the key points described in detail throughout the chapter. Problems to Solve: These problems test a student’s ability to apply the infor- mation covered in a particular chapter. Detailed answers are provided in an appendix in the back of the book. Simbryo: New to this edition, Simbryo, located in the back of the book, is an interactive CD-ROM that demonstrates normal embryologic events and the origins

This is a short excerpt from the opening of “” by Unknown, quoted for review and introduction purposes. All rights belong to the copyright holders.

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