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A neuroscientist is investigating the development of the nervous system. In his experiments, he microinjects a dye into the embryo of an animal subject in vivo. After birth, he performs histological studies to determine the destination of the dye. In one animal subject, he
locates the dye in the dorsal horn of the spinal cord. Which of the following locations in the embryo was the most likely site of the injection?
A. Alar plate
B. Basal plate
C. Neural crest
D. Rostral end of neural tube
E. Sulcus limitans
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The correct answer is A. The spinal cord arises from the caudal end of the neural tube. During development, an alar and a basal plate is formed, separated by a longitudinal groove called the sulcus limitans (choice E).
The alar plate forms the dorsal (posterior) part of the spinal cord and becomes the sensory or afferent portion of the cord. The basal plate (choice B) is the ventral (anterior) part of the cord, and becomes the motor, or efferent, portion of the spinal cord, and therefore would contain anterior horn cells.
The neural crest (choice C) develops into multipolar ganglion cells of autonomic ganglia, pseudounipolar cells of spinal and cranial nerve ganglia, leptomeningeal cells, Schwann cells, melanocytes, chromaffin cells of the adrenal medulla, and odontoblasts.
The brain forms from the rostral end of the neural tube (choice D).
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A. Alar plate - sensory - dorsal horn of spinal cord
