Which muscles are associated with S1 sensory innervation?

• A. Gastrocnemius and Soleus
• B. Extensor digitorum longus
• C. Tibialis anterior
• D. Flexor hallucis longus

Answer: (A)

The sensory innervation associated with the S1 nerve root primarily affects areas of the lower limb, particularly the lateral aspect of the foot and parts of the calf. The gastrocnemius and soleus muscles, which make up the calf muscles, are innervated by the tibial nerve, a branch of the sciatic nerve that carries fibers from the S1 nerve root.

Additionally, the S1 nerve root is responsible for the sensory innervation of the lateral aspect of the foot and the heel, areas that correspond with the functions of the gastrocnemius and soleus during movement, such as plantar flexion. This is how the muscles relate to sensory innervation from the S1 nerve root. In contrast, the other options presented do not have the same direct association with S1 sensory functions. For instance, the extensor digitorum longus and tibialis anterior are primarily innervated by the deep peroneal nerve, primarily associated with the L4-L5 levels. Flexor hallucis longus, while important for action in the foot, does not have a significant sensory innervation role related to the S1 region.

Thus, the connection of the gastrocnemius and soleus muscles to the S