1 Introduction to the Developing Human 1
Developmental Periods 1
Significance of Embryology 5
Historical Gleanings 6
Ancient Views of Human Embryology 6
Embryology in the Middle Ages 6
The Renaissance 7
Genetics and Human Development 8
Molecular Biology of Human Development 10
Descriptive Terms in Embryology 10
Clinically Oriented Problems 10
2 First Week of Human Development 13
Gametogenesis 14
Meiosis 14
Spermatogenesis 14
Oogenesis 19
Prenatal Maturation of Oocytes 19
Postnatal Maturation of Oocytes 19
Comparison of Gametes （Sex Cells） 19
Uterus, Uterine Tubes, and Ovaries 19
Uterus 19
Uterine Tubes 20
Ovaries 20
Female Reproductive Cycles 20
Ovarian Cycle 23
Follicular Development 23
Ovulation 24
Corpus Luteum 25
Menstrual Cycle 26
Phases of the Menstrual Cycle 26
Transportation of Gametes 27
Oocyte Transport 27
Sperm Transport 27
Maturation of Sperms 28
Viability of Gametes 29
Fertilization 30
Phases of Fertilization 30
Fertilization 31
Cleavage of Zygote 32
Formation of Blastocyst 35
Summary of First Week 37
Clinically Oriented Problems 38
3 Second Week of Human Development 41
Completion of Implantation of Blastocyst 41
Formation of Amniotic Cavity, EmbryonicDisc, and Umbilical Vesicle 43
Development of Chorionic Sac 44
Implantation Sites of Blastocysts 48
Summary of Implantation 48
Summary of Second Week 51
Clinically Oriented Problems 51
4 Third Week of Human Development 53
Gastrulation: Formation of Germ Layers 54
Primitive Streak 54
Fate of Primitive Streak 56
Notochordal Process and Notochord 57
Allantois 58
Neurulation: Formation of Neural Tube 61
Neural Plate and Neural Tube 61
Neural Crest Formation 61
Development of Somites 63
Development of Intraembonic Coelom 64
Early Development of Cardiovascular System 64
Vasculogenesis and Angiogenesis 64
Primordial Cardiovascular System 64
Development of Chorionic Villi 65
Summary of Third Week 66
Clinically Oriented Problems 69
5 Fourth to Eighth Weeks of Human Development 71
Phases of Embryonic Development 71
Folding of Embryo 72
Folding of Embryo in the Median Plane 72
Folding of Embryo in the Horizontal Plane 72
Germ Layer Derivatives 72
Control of Embryonic Development 74
Highlights of Fourth to Eighth Weeks 76
Fourth Week 76
Fifth Week 77
Sixth Week 77
Seventh Week 80
Eighth Week 86
Estimation of Embryonic Age 89
Summary of Fourth to Eighth Weeks 89
Clinically Oriented Problems 90
6 Ninth Week to Birth: The Fetal Period 93
Estimation of Fetal Age 95
Trimesters of Pregnancy 95
Measurements and Characteristics of Fetuses 95
Highlights of Fetal Period 96
Nine to Twelve Weeks 96
Thirteen to Sixteen Weeks 97
Seventeen to Twenty Weeks 98
Twenty-One to Twenty-Five Weeks 98
Twenty-Six to Twenty-Nine Weeks 99
Thirty to Thirty-Four Weeks 99
Thirty-Five to Thirty-Eight Weeks 99
Expected Date of Delivery 101
Factors Influencing Fetal Growth 101
Cigarette Smoking 101
Multiple Pregnancy 101
Alcohol and Illicit Drugs 101
Impaired Uteroplacental and Fetoplacental Blood Flow 102
Genetic Factors and Growth Retardation 102
Procedures for Assessing Fetal Status 102
Ultrasonography 102
Diagnostic Amniocentesis 102
Alpha- Fetoprotein Assay 103
Spectrophotometric Studies 103
Chorionic Villus Sampling 104
Sex Chromatin Patterns 104
Cell Cultures and Chromosomal Analysis 104
Fetal Transfusion 104
Fetoscopy 105
Percutaneous Umbilical Cord Blood Sampling 105
Magnetic Resonance Imaging 105
Fetal Monitoring 105
Summary of Fetal Period 105
Clinically Oriented Problems 106
7 Placenta and Fetal Membranes 109
Placenta 109
Decidua 110
Development of Placenta 110
Placental Circulation 113
Placental Membrane 114
Functions of Placenta 116
Placental Endocrine Synthesis and Secretion 119
Placenta as an Invasive Tumor-like Structure 120
Uterine Growth during Pregnancy 121
Parturition 121
Placenta and Fetal Membranes after Birth 123
Maternal Surface of Placenta 123
Fetal Surface of Placenta 123
Umbilical Cord 126
Amnion and Amniotic Fluid 127
Umbilical Vesicle 132
Significance of Umbilical Vesicle 132
Fate of Umbilical Vesicle 132
Allantois 132
Multiple Pregnancies 133
Twins and Fetal Membranes 133
Dizygotic Twins 134
Monozygotic Twins 134
Other Types of Multiple Births 138
Summary of Placenta and Fetal Membranes 141
Clinically Oriented Problems 142
8 Body Cavities and Diaphragm 145
Embryonic Body Cavity 145
Mesenteries 148
Division of Embryonic Body Cavity 149
Development of the Diaphragm 151
Septum Transversum 151
Pleuroperitoneal Membranes 151
Dorsal Mesentery of the Esophagus 152
Muscular Ingrowth from the Lateral Body Walls 152
Positional Changes and Innervation of the Diaphragm 152
Summary of Development of the Body Cavities and Diaphragm 157
Clinically Oriented Problems 157
9 Pharyngeal Apparatus, Face, and Neck 159
Pharyngeal Arches 159
Pharyngeal Arch Components 161
Pharyngeal Pouches 162
Derivatives of Pharyngeal Pouches 166
Pharyngeal Grooves 169
Pharyngeal Membranes 169
Development of Thyroid Gland 173
Histogenesis of Thyroid Gland 174
Development of Tongue 176
Lingual Papillae and Taste Buds 177
Nerve Supply of Tongue 177
Development of Salivary Glands 179
Development of Face 179
Summary of Facial Development 186
Development of Nasal Cavities 186
Paranasal Sinuses 187
Development of Palate 188
Primary Palate 188
Secondary Palate 188
Summary of Pharyngeal Apparatus, Face, and Neck 196
Clinically Oriented Problems 197
10 Respiratory System 199
Respiratory Primordium 199
Development of Larynx 200
Development of Trachea 202
Development of Bronchi and Lungs 204
Maturation of Lungs 206
Summary of Respiratory System 210
Clinically Oriented Problems 210
11 Alimentary System 213
Foregut 214
Development of Esophagus 214
Development of Stomach 215
Omental Bursa 215
Development of Duodenum 219
Development of Liver and Biliary Apparatus 221
Development of Pancreas 223
Development of Spleen 225
Midgut 227
Herniation of Midgut Loop 227
Rotation of Midgut Loop 227
Retraction of Intestinal Loops 227
Cecum and Appendix 230
Hindgut 238
Cloaca 238
Anal Canal 240
Summary of Alimentary System 243
Clinically Oriented Problems 243
12 Urogenital System 245
Development of Urinary System 247
Development of Kidneys and Ureters 247
Development of Urinary Bladder 259
Development of Urethra 264
Development of Suprarenal Glands 264
Development of Genital System 265
Development of Gonads 265
Development of Genital Ducts 269
Development of Male Genital Ducts and Glands 269
Development of Female Genital Ducts and Glands 271
Development of Vagina 271
Development of External Genitalia 273
Development of Male External Genitalia 273
Development of Female External Genitalia 275
Development of Inguinal Canals 282
Relocation of Testes and Ovaries 284
Testicular Descent 284
Ovarian Descent 284
Summary of Urogenital System 285
Clinically Oriented Problems 286
13 Cardiovascular System 289
Early Development of the Heart and Blood Vessels 290
Development of Veins Associated with Embryonic Heart 290
Fate of Vitelline and Umbilical Arteries 295
Later Development of the Heart 295
Circulation through the Primordial Heart 298
Partitioning of Primordial Heart 300
Changes in Sinus Venosus 304
Conducting System of Heart 312
Birth Defects of the Heart and Great Vessels 313
Derivatives of Pharyngeal Arch Arteries 324
Derivatives of First Pair of Pharyngeal Arch Arteries 324
Derivatives of Second Pair of Pharyngeal Arch Arteries 324
Derivatives of Third Pair of Pharyngeal Arch Arteries 325
Derivatives of Fourth Pair of Pharyngeal Arch Arteries 325
Fate of Fifth Pair of Pharyngeal Arch Arteries 325
Derivatives of Sixth Pair of Pharyngeal Arch Arteries 327
Pharyngeal Arch Arterial Birth Defects 327
Fetal and Neonatal Circulation 333
Fetal Circulation 333
Transitional Neonatal Circulation 333
Derivatives of Fetal Vessels and Structures 337
Development of Lymphatic System 339
Development of Lymph Sacs and Lymphatic Ducts 339
Development of Thoracic Duct 340
Development of Lymph Nodes 340
Development of Lymphocytes 340
Development of Spleen and Tonsils 340
Summary of Cardiovascular System 340
Clinically Oriented Problems 341
14 Skeletal System 343
Development of Bone and Cartilage 343
Histogenesis of Cartilage 345
Histogenesis of Bone 345
Membranous Ossification 345
Enclochondral Ossification 346
Development of Joints 346
Fibrous Joints 346
Cartilaginous Joints 348
Synovial Joints 348
Development of Axial Skeleton 348
Development of Vertebral Column 348
Development of Ribs 350
Development of Sternum 351
Development of Cranium 351
Cranium of Neonate 351
Postnatal Growth of Cranium 352
Development of Appendicular Skeleton 357
Summary of Skeletal System 360
Clinically Oriented Problems 360
15 Muscular System 363
Development of Skeletal Muscle 363
Myotomes 365
Pharyngeal Arch Muscles 366
Ocular Muscles 366
Tongue Muscles 366
Limb Muscles 366
Development of Smooth Muscle 366
Development of Cardiac Muscle 367
Summary of Muscular System 369
Clinically Oriented Problems 369
16 Development of Limbs 371
Early Stages of Limb Development 371
Final Stages of Limb Development 375
Cutaneous Innervation of Limbs 375
Blood Supply of Limbs 380
Birth Defects of Limbs 382
Summary of Limb Development 386
Clinically Oriented Problems 386
17 Nervous System 389
Development of Nervous System 389
Development of Spinal Cord 392
Development of Spinal Ganglia 394
Development of Meninges 394
Positional Changes of Spinal Cord 395
Myelination of Nerve Fibers 398
Birth Defects of Spinal Cord 398
Development of Brain 404
Brain Flexures 404
Hindbrain 404
Choroid Plexuses and Cerebrospinal Fluid 406
Midbrain 407
Forebrain 408
Birth Defects of Brain 414
Development of Peripheral Nervous System 423
Spinal Nerves 423
Cranial Nerves 424
Development of Autonomic Nervous System 425
Sympathetic Nervous System 425
Parasympathetic Nervous System 426
Summary of Nervous System 426
Clinically Oriented Problems 426
18 Development of Eyes and Ears 429
Development of Eyes and Related Structures 429
Development of Retina 431
Development of Ciliary Body 435
Development of Iris 435
Development of Lens 437
Development of Aqueous Chambers 438
Development of Cornea 440
Development of Choroid and Sclera 440
Development of Eyelids 440
Development of Lacrimal Glands 441
Development of Ears 441
Development of Internal Ear 441
Development of Middle Ear 443
Development of External Ear 444
Summary of Development of Eyes 448
Summary of Development of Ears 448
Clinically Oriented Problems 448
19 Integumentary System 451
Development of Skin andAppendages 451
Epidermis 452
Dermis 454
Development of Glands 454
Development of Hairs 459
Development of Nails 460
Development of Teeth 460
Summary of Integumentary System 468
Clinically Oriented Problems 468
20 Human Birth Defects 471
Classification of Birth Defects 471
Teratology: Study of Abnormal Development 472
Birth Defects Caused by Genetic Factors 472
Numerical Chromosomal Abnormalities 473
Structural Chromosomal Abnormalities 481
Birth Defects Caused by Mutant Genes 484
Developmental Signaling Pathways 486
Birth Defects Caused by Environmental Factors 487
Principles of Teratogenesis 487
Critical Periods of Human Development 487
Human Teratogens 491
Birth Defects Caused by Multifactorial Inheritance 499
Summary of Human Birth Defects 499
Clinically Oriented Problems 500
21 Common Signaling Pathways UsedDuring Development 503
Intercellular Communication 504
Gap Junctions 504
Cell Adhesion Molecules 505
Morphogens 506
Retinoic Acid 506
Transforming Growth Factor β/Bone Morphogenetic Protein 506
Hedgehog 507
Wnt/β-Catenin Pathway 507
Receptor Tyrosine Kinases 509
Common Features 509
Regulation of Angiogenesis by Receptor Tyrosine Kinases 510
Notch-Delta Pathway 510
Transcription Factors 511
Hox/Homeobox Proteins 511
Pax Genes 511
Basic Helix-Loop-Helix Transcription Factors 512
Epigenetics 512
Histone Acetylation 512
DNA Methylation 512
Stem Cells: Differentiation versus Pluripotency 513
Summary of Common Signaling Pathways Used Durinq Development 514
Appendix 516
Index 526