In the first part of this article, the anatomy and histology of the peripheral nerves are discussed, emphasizing the importance
of the correlation with their imaging appearance. The normal appearance of a nerve and the ultrasound exploration technique
are presented. In the second part, the ultrasonographic study of upper extremity entrapment neuropathies is reviewed.
Keywords: Peripheral nerves. Ultrasound. Neuropathies. Entrapment.