Types of neural cells in the spinal ganglia of human embryos and early fetuses.
Spinal ganglial of human embryos and fetuses ranging in C.-R. length from 15 to 74 mm and in age from 6 1/2 to 11 postovulatory weeks were studied by light and electron microscopy. A sequence of events in differentiation and maturation enabled five types of cells to be distinguished: 1. apolar, undifferentiated neuroblasts are the main cells at 6 1/2 to 7 1/2 weeks; 2. early bipolar neuroblasts (strictly speaking, types 2 to 5 are immature neurons) predominate at the end of the embryonic period proper (8 postovulatory weeks); 3. intermediate bipolar neuroblasts are characteristic of the early fetal period; 4. late bipolar neuroblasts, in which two proceses arise separately from one pole of the cell, appear at about 10 postovulatory weeks; 5. unipolar neuroblasts are found within another week and, by that time, cells of types 1 and 2 are no longer present.
D002454:Cell Differentiation; D002467:Cell Nucleus / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D005727:Ganglia, Spinal / Q000196:embryology* / Q000648:ultrastructure; D005865:Gestational Age; D006056:Golgi Apparatus / Q000648:ultrastructure; D006801:Humans; D008928:Mitochondria / Q000648:ultrastructure; D009474:Neurons / Q000648:ultrastructure*; D011132:Polyribosomes / Q000648:ultrastructure