The ethmoidal nerves are branches of the nasociliary nerve, which is a part of the trigeminal nerve (cranial nerve V). These nerves primarily provide sensory innervation to the nasal cavity and parts of the ethmoid bone, contributing to the sense of smell and sensation in the nasal region. There are two main types of ethmoidal nerves: the anterior and posterior ethmoidal nerves. The anterior ethmoidal nerve supplies sensation to the anterior part of the nasal cavity, while the posterior ethmoidal nerve innervates the posterior part. Both play a crucial role in the overall sensory function of the nasal area.