Knowledge of the embryological development of metamers is of great importance for the understanding of the concept of “segment.” The segment is composed, in turn, of embryological derivatives of these metamers, such as dermatomes, myotomes, sclerotomes, and viscerotomes. The different parts of the segment are in obvious connection and are the morphological support of the pathophysiological reflexes that arise from any part of each segment. When a viscera or organ is pathologically altered, its expression occurs through the other parts of the same segment of embryological origin. In the case of the skin, dermatomes, according to Henry Head, are areas that have a segmental distribution and that, when they converge, form zones that are in semiological relationship with certain organs. According to James Mackenzie, deep tissues such as muscles, bones, tendons, and joints can also have semiological changes in the cases of visceral disease. In this chapter, the dermatomic, myotomic, sclerotomic, and viscerotomic segmental relationships of each organ of the face, neck, trunk, and pelvis are shown, which are the foundation for the physical examination, diagnosis, and treatment of segmental disorders in neural therapy medicine.