Dermatomes of Upper Limb and Segmental Nerve Function Anatomy Note: Schematic demarcation of dermatomes (modified from Keegan and Garrett) shown as distinct segments. There is considerable overlap between adjacent dermatomes. Abduction C8–T1, Adduction C5, 6 Flexion C7, 8 Extension C7–T1 Flexion C7–T1 Flexion C8–T1 Flexion C8–T1 Opposition C7–T1 Reposition C6–8 Pronation C5–7 Supination Flexion Extension C7, 8 Extension.