Embryology at a Glance

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Embryology at a GlanceSecond Edition

Samuel WebsterSenior Lecturer in Anatomy & EmbryologyMedical SchoolSwansea UniversitySwansea, UK

Rhiannon de WreedeHonorary LecturerCollege of MedicineSwansea UniversitySwansea, UK

This edition first published 2016 © 2016 by John Wiley & Sons, LtdPrevious edition © 2012 John Wiley & Sons, Ltd

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Cover image: ©Steve Atherton

Set in 9.5/11.5pt Minion by SPi Global, Pondicherry, India

1 2016

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Contents

Preface   viiAcknowledgements   viiiList of abbreviations   ixTimeline   xAbout the companion website   xi

Part 1 Early development   1 1 Embryology in medicine   2 2 Language of embryology   4 3 Introduction to development   6 4 Cell signalling genes   8 5 Embryonic and foetal periods   10 6 Mitosis   12 7 Meiosis   14 8 Spermatogenesis   16 9 Oogenesis   1810 Fertilisation   2011 From zygote to blastocyst   2212 Implantation   2413 Placenta   2614 Gastrulation   2815 Germ layers   3016 Stem cells   3217 Neurulation   3418 Neural crest cells   3619 Body cavities (embryonic)   3820 Folding of the embryo   4021 Segmentation   4222 Somites   44

Part 2 Systems development   4723 Skeletal system (ossification)   4824 Skeletal system   5025 Muscular system   5226 Musculoskeletal system: limbs   5427 Circulatory system: heart tube   5628 Circulatory system: heart chambers   5829 Circulatory system: blood vessels   6030 Circulatory system: embryonic veins   6231 Circulation system: changes at birth   6432 Respiratory system   6633 Digestive system: gastrointestinal tract   6834 Digestive system: associated organs   7035 Digestive system: congenital anomalies   7236 Urinary system   74

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37 Reproductive system: ducts and genitalia   7638 Reproductive system: gonads   7839 Endocrine system   8040 Head and neck: arch I   8241 Head and neck: arch II   8442 Head and neck: arch III   8643 Head and neck: arches IV–VI   8844 Central nervous system   9045 Peripheral nervous system   9246 The ear   9447 The eye   9648 Antenatal screening   98

Self-assessment MCQs   100Self-assessment MCQ answers   104Self-assessment EMQs   105Self-assessment EMQ answers   107Glossary   108Index   112

vii

Preface

We wrote this book for our students; those studying medicine with us, those listening to the podcasts wherever they may be, and those studying the other forms that biology takes

on their paths to whatever goals they may have in life. We have introduced many students to the fascinating and often surprising processes of embryological development, and we hope to do the same in this book. It is written for anyone wondering, “where did I come from?”

The content of this book extends beyond the curricula of most medicine, health and bioscience teaching programmes in terms of breadth, but we have limited its depth. Many embryology textbooks cover development in detail, but students struggle to get started,

and to get to grips with early concepts. Hopefully we have addressed these difficulties with this book.

We hope that you will use this book to begin your studies of embryology and development, but also that you will return to it when preparing for assessments or checking your understanding. You will find example assessment questions at the end of the book as well as a Glossary.

Let this be the start of your integration of embryonic development with anatomy, to the ends of improved understanding and better patient care or scientific insight.

Samuel WebsterRhiannon de Wreede

viii

Acknowledgements

Thank you to Kim and Robin for being so encouraging and putting up with the time demands of completing this book. We would also like to thank the editors at Wiley‐Blackwell

for leading us through this process and for their support and encouragement, and Jane Fallows for all her work with the illustrations.

ix

List of abbreviations

AER Apical ectodermal ridgeCAM Cell adhesion moleculeCN Cranial nerveCSF Cerebrospinal fluidECMO Extracorporeal membrane oxygenationFGF Fibroblast growth factorFSH Follicle stimulating hormoneGnRH Gonadotrophin releasing hormoneHbF Foetal haemoglobinhCG Human chorionic gonadotrophinhCS Human chorionic somatomammotrophinIUD Intrauterine device – contraceptive deviceIUGR Intrauterine growth restriction

IVC Inferior vena cavaIVD Intervertebral discIVF In vitro fertilisationLH Luteinising hormoneLMP Last menstrual periodPDA Patent ductus arteriosusPFO Patent foramen ovalePTH Parathyroid hormonePZ Proliferating zoneRh RhesusSVC Superior vena cavaTGF Transforming growth factorZPA Zone of polarising activity

x

Timeline

Language of embryology (Chapter 2)

Introduction to development (Chapter 3)

Embryonic and foetal periods (Chapter 5)

Spermatogenesis (Chapter 7)

Oogenesis (Chapter 8)

Fertilisation (Chapter 10)

From zygote to blastocyst (Chapter 11)

Implantation (Chapter 12)

Placenta (Chapter 13)

Gastrulation (Chapter 14)

Formation of germ layers (Chapter 15)

Formation of the heart tube (Chapter 27)

Folding of the embryo (Chapter 20)

Neurulation (Chapter 17)

Segmentation (Chapter 21)

Formation of blood vessels (Chapter 29)

Somite development (Chapter 22)

Development of digestive system (Chapter 33)

Development of body cavities (Chapter 19)

Development of urinary system (Chapter 36)

Development of head and neck structures (Chapter 40–43)

Development of the eye (Chapter 47)

Migration of neural crest cells (Chapter 18)

Development of muscular system (Chapter 25)

Development of the ear (Chapter 46)

Development of central nervous system (Chapter 44)

Cranial neuropore closes (Chapter 17)

Development of endocrine system (Chapter 39)

Caudal neuropore closes (Chapter 17)

Heart tube divides into four chambers (Chapter 28)

Development of skeletal system (Chapter 24)

Development of peripheral nervous system (Chapter 45)

Development of musculoskeletal system (Chapter 26)

Development of respiratory system (Chapter 32)

Formation of the atrial septa (Chapter 28)

Ossification of skeletal system (Chapter 22)

Development of reproductive system (Chapter 37)

Foetus can hear external sounds (Chapter 46)

0 10 20 30Days Weeks

40 50 60 10 20 30 40Death

Menopause

Days Weeks Adult

PubertyAdult

0 10 20 30 40 50 60 10 20 30 40Death

Puberty Menopause

xi

About the companion website

Don’t forget to visit the companion website for this book:

www.ataglanceseries.com/embryology

There you will find valuable material designed to enhance your learning, including:

• Podcasts and animations hosted on Dr Webster’s website • An additional instructor resource comprising an image bank of all the figures from the book.

Scan this QR code to visit the companion website