Lower Limb, N469 Notes, Anatomy, Lower Limb, Topographic Anatomy. Lower Limb, N470 Notes, Anatomy, Lower Limb, Cutaneous Anatomy

Lower Limb, N469 Notes, Anatomy, Lower Limb, Topographic Anatomy

Lower Limb, N470 Notes, Anatomy, Lower Limb, Cutaneous Anatomy

• Whats the difference between a Dermatome and an Autonomous Sensory zone
• With few exceptions, there is complete overlap between adjacent dermatomes. This means that the loss of a single nerve root rarely produces significant loss of skin sensitivity. The exception to this rule is found in small patches in the distal extremities, which have been termed "autonomous zones." In these regions single nerve roots supply distinct and non-overlapping areas of skin. By their nature the "autonomous zones" represent only a small portion of any dermatome and only a few nerve roots have such autonomous zones. For example, the C5 nerve root may be the sole supply to an area of the lateral arm and proximal part of the lateral forearm. The C6 nerve root may distinctly supply some skin of the thumb and index finger. Injuries to the C7 nerve root may decrease sensation over the middle and sometimes the index finger along with a restricted area on the dorsum of the hand. C8 nerve root lesions can produce similar symptoms over the small digit occasionally extending into the hypothenar area of the hand. In the lower limb, L4 nerve root damage may decrease sensation over the medial part of the leg, while L5 lesions affect sensation over part of the dorsum of the foot and great toe. S1 nerve root lesions typically decrease sensation on the lateral side of the foot.