ABSTRACT
Throughout the length of the neural tube, primitive neuroectodermal cells proliferate and differentiate into neurons, astrocytes, oligodendrocytes, and ependymal cells. Neuronal precursors (neuroblasts) migrate to their genetically coded location, guided by adhesion molecules and glial cells. T he axons grow toward their targets and establish specific synaptic connections with the appro priate neurons. These connections are stabilized by the activity of the synapse and the presence o f target-derived factors. The strength o f these connections continues to
Fig. 2.3. Subdivisions of the primitive nervous system and their derivatives in the adult brain, as shown in a midsagittal magnetic resonance image of the brain. (Modified from Benarroch EE. Basic neurosciences with clinical applications. Philadelphia: Elsevier; 2006. Used with permission of Mayo Foundation for Medical Education and Research.)
Table 2.1. Derivatives of the Neural Tube and Neural Crest
Supratentorial Prosencephalon (forebrain) Telencephalon
Diencephalon
Cerebral cortex Basal ganglia Thalamus Hypothalamus Pineal gland Neurohypophysis Retina
Lateral ventricle
Third ventricle
Posterior fossa Mesencephalon (midbrain) Mesencephalon Rhombencephalon (hindbrain) Metencephalon
Myelencephalon
Midbrain Pons Cerebellum Medulla
Aqueduct of Sylvius Fourth ventricle
Fourth ventricle Spinal Peripheral
Caudal neural tube Neural crest
Spinal cord Neural crest
Spinal cord Dorsal root ganglia Autonomic ganglia Adrenal medulla Enteric nervous system Schwann cells
Central canal
elements in the adult nervous system listed in Table 2 .1 . The caudal end o f the neural tube undergoes much less modification as it forms the spinal cord. A central rem nant o f the internal cavity of the neural tube remains in each o f these derivatives and forms the different compo nents o f the ventricular system (Fig. 2.5).
