Mammalian Axis Formation 311 Experimental analysis of the Hox code 315 The anterior-posterior axis: Two signaling The Dorsal-Ventral and Left-Right Axes 316 centers 311 The dorsal-ventral axis 316 Anterior-posterior patterning by FGF and retinoic acid gradients 312 Coda 319 Anterior-posterior patterning: The Hox code hypothesis 314 PART THE STEM CELL CONCEPT Introducing Organogenesis 323 The Stem Cell Concept 323 Mesenchymal Stem Cells: Multipotent Stem Cell Vocabulary 326 Adult Stem Cells 330 Adult stem Cells 327 A New Perspective on Organogenesis 331 Adult Stem Cell Niches 328 chAPTER 9 Cell Differentiation in the vertebrate Eye 362 The Emergence of the ectoderm Neural retina differentiation 362 Lens and cornea differentiation 364 Central Nervous System and Epidermis 333 THE EPIDERMIS AND ITS CUTANEOUS APPENDAGES 365 Establishing the Neural Cells 333 CONSTRUCTING THE CENTRAL NERVOUS Origin of the Epidermis 365 SYSTEM 334 The Cutaneous Appendages 366 Formation of the neural tube 334 I SIDELIGHTS SPECULATIONS EDAR Syndromes 369 Primary neurulation 335 Secondary neurulation CHAPTER 10 BUILDING THE BRAIN Neural Crest Cells and axonal Differentiation of the Neural Tube 341 The anterior-posterior axis 341 Specificity 373 The dorsal-ventral axis 343 THE NEURAL CREST 373 Differentiation of Neurons in the Brain 345 Specification of Neural Crest Cells 374 Tissue Architecture of the Central Nervous System 34 Regionalization of the Neural Crest 376 Spinal cord and medulla organization 349 Trunk Neural Crest 3 Cerebellar organization 350 Migration pathways of trunk neural crest cells 377 Cerebral organization 351 The mechanisms of trunk neural crest migration 378 H SIDELIGHTS SPECULATIONS Adult Neural Stem The ventral pathway 379 Cells 354 The dorsolateral migration pathway 382 I SIDELIGHTS SPECULATIONS The Unique Development Cranial Neural Crest 383 of the human brain 356 Intramembranous ossification: Neural crest-derive DEVELOPMENT OF THE VERTEBRATE EYE 359 head skeleton 385 The Dynamics of Optic Development 359 Coordination of face and brain growth 387 Formation of the Eye Field 359 Tooth formation 388 Cardiac Neural Crest 388V_1^IN I CiN I O Mammalian Axis Formation 311 The anterior-posterior axis: Two signaling centers 311 Anterior-posterior patterning by FGF and retinoic acid gradients 312 Anterior-posterior patterning: The Hox code hypothesis 314 Experimental analysis of the Hox code 315 The Dorsal-Ventral and Left-Right Axes 316 The dorsal-ventral axis 316 The left-right axis 317 Coda 319 PART THE STEM CELL CONCEPT Introducin Organogenesis 323 The Stem Cell Concept 323 Stem Cell Vocabulary 326 Adult Stem Cells 327 Adult Stem Cell Niches 328 Mesenchymal Stem Cells: Multipotent Adult Stem Cells 330 A New Perspective on Organogenesis 331 CHAPTER 9 The Emergence of the Ectoderm: Central Nervous System and Epidermis 333 Establishing the Neural Cells 333 CONSTRUCTING THE CENTRAL NERVOUS SYSTEM 334 Formation of the Neural Tube 334 Primary neurulation 335 Secondary neurulation 340 BUILDING THE BRAIN 341 Differentiation of the Neural Tube 341 The anterior-posterior axis 341 The dorsal-ventral axis 343 Differentiation of Neurons in the Brain 345 Tissue Architecture of the Central Nervous System 348 Spinal cord and medulla organization 349 Cerebellar organization 350 Cerebral organization 351 • SIDELIGHTS & SPECULATIONS Adult Neural Stem Cells 354 • SIDELIGHTS & SPECULATIONS The Unique Development of the Human Brain 356 DEVELOPMENT OF THE VERTEBRATE EYE 359 The Dynamics of Optic Development 359 Formation of the Eye Field 359 Cell Differentiation in the Vertebrate Eye 362 Neural retina differentiation 362 Lens and cornea differentiation 364 THE EPIDERMIS AND ITS CUTANEOUS APPENDAGES 365 Origin of the Epidermis 365 The Cutaneous Appendages 366 • SIDELIGHTS & SPECULATIONS EDAR Syndromes 369 CHAPTER 10 Neural Crest Cells andAxonal Specificity 373 THE NEURAL CREST 373 Specification of Neural Crest Cells 374 Regionalization of the Neural Crest 376 Trunk Neural Crest 377 Migration pathways of trunk neural crest cells 377 The mechanisms of trunk neural crest migration 378 The ventral pathway 379 The dorsolateral migration pathway 382 Cranial Neural Crest 383 Intramembranous ossification: Neural crest-derived head skeleton 385 Coordination of face and brain growth 387 Tooth formation 388 Cardiac Neural Crest 388