Download Slide ()

The hindbrain and spinal cord are segmented structures. In the caudal brain stem the segments are called rhombomeres; in the spinal cord they are called
body somites. Four occipital somites form structures of the head. These are shown in the caudal medulla (A). A. The position of the developing nervous
system in the embryo is illustrated as well as the segmental organization of rhombomeres and somites. The cranial nerves that contain the axons of brain
stem motor neurons are also shown. From rostral to caudal the following cranial nerves are illustrated: IV, V VI, VII, IX, X, and XII. The two mesencephalic
segments and the segment between the metacephalon and mesencephalon are not shown. B. Drawing of a single spinal cord segment from the mature
nervous system. C. Lateral view of the mature spinal cord in the vertebral canal. Note that the spinal nerves exit from the vertebral canal through
Source: Somatic Sensation: Spinal Mechanosensory Systems, Neuroanatomy Text and Atlas, 4e
intervertebral foramina. (A, Adapted from Lumsden A. The cellular basis of segmentation in the developing hindbrain. Trends Neurosci. 1990;13[8]:329–
Citation: Martin JH. Neuroanatomy Text and Atlas, 4e; 2016 Available at: http://mhmedical.com/ Accessed: May 07, 2017
335.)
Copyright © 2017 McGraw-Hill Education. All rights reserved