title: Features of the developing brain.
abstract: BACKGROUND
  Fetal brain evaluation implies a perfect knowledge of the timing and characteristics of the developing nervous system during gestation.
  
  
  CONCLUSIONS
  The first half of gestation corresponds to the neurulation, differentiation of primary cerebral vesicles, and neuronogenesis. The second half is characterized by the tremendous growth of the cerebral hemispheres and the settlement of gyral formation, while the ventricular system undergoes gradual narrowing. Gyral formation follows an invariable temporospatial schedule and is a good marker of fetal maturation. At the histological level, the fetal cortex displays transient developmental features, a superficial granular layer, and cells of Cajal-Retzius, which disappear at term. Neuroblasts formation has usually ceased by the 16th week of gestation, while neuronal migration continues until the extinction of the germinal layer. At this time, the remnant of the germinal layer constitutes, between the thalami and the caudate nucleus, an eminence of tightly packed cells, called the ganglionic eminence or germinal zone. They disappear by the age of 1 year.
authors.affiliation: Service Histologie-Embryologie-Cytogénétique, Groupe Hospitalier Necker Enfants-Malades, 149 Rue de Sèvres, 75743 Paris Cedex 15, France. ferechte.razavi@nck.ap-hop-paris.fr
authors.forename: Férechté
authors.initials: F
authors.lastname: Encha-Razavi
authors.forename: Pascale
authors.initials: P
authors.lastname: Sonigo
mesh_terms: D000375:Aging; D017209:Apoptosis; D001921:Brain / Q000166:cytology / Q000196:embryology*; D002552:Cerebral Ventricles / Q000196:embryology; D002831:Choroid Plexus / Q000196:embryology; D005314:Embryonic and Fetal Development; D005333:Fetus; D006801:Humans; D008279:Magnetic Resonance Imaging; D009457:Neuroglia / Q000502:physiology; D009474:Neurons / Q000502:physiology