Neural Crest Cells

During elevation of the neural plate, a group of cells appears along each edge (the crest) of the neural folds (Fig. 19.2). These neural crest cells are ectodermal

Figure 19.11 Origin of the nerve cell and the various types of glial cells. Neuroblasts, fibrillar and protoplasmic astrocytes, and ependymal cells originate from neuroepithelial cells. Microglia develop from mesenchyme cells. The origin of the oligodendroglia is not clear.

Mesenchyme Neuroepithelium

Figure 19.11 Origin of the nerve cell and the various types of glial cells. Neuroblasts, fibrillar and protoplasmic astrocytes, and ependymal cells originate from neuroepithelial cells. Microglia develop from mesenchyme cells. The origin of the oligodendroglia is not clear.

Multipolar neuroblast

Protoplasmic Fibrillar astrocyte astrocyte

Multipolar neuroblast

Protoplasmic Fibrillar astrocyte astrocyte in origin and extend throughout the length of the neural tube. Crest cells migrate laterally and give rise to sensory ganglia (dorsal root ganglia) of the spinal nerves and other cell types (Fig. 19.2).

During further development, neuroblasts of the sensory ganglia form two processes (Fig. 19.10A). The centrally growing processes penetrate the dorsal portion of the neural tube. In the spinal cord, they either end in the dorsal horn or ascend through the marginal layer to one of the higher brain centers. These processes are known collectively as the dorsal sensory root of the spinal nerve (Fig. 19.105). The peripherally growing processes join fibers of the ventral motor roots and thus participate in formation of the trunk of the spinal nerve. Eventually these processes terminate in the sensory receptor organs. Hence, neuroblasts of the sensory ganglia derived from neural crest cells give rise to the dorsal root neurons.

In addition to forming sensory ganglia, cells of the neural crest differentiate into sympathetic neuroblasts, Schwann cells, pigment cells, odontoblasts, meninges, and mesenchyme of the pharyngeal arches (see Chapter 5).

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Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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