The infratrochlear nerve primarily affects which area?

The infratrochlear nerve is a branch of the nasociliary nerve, which itself is a branch of the ophthalmic division of the trigeminal nerve. This nerve primarily innervates the skin and mucous membranes in the area of the nose. Specifically, it provides sensory innervation to the skin at the tip and sides of the nose, as well as the conjunctiva of the eye and the lacrimal sac, making it crucial for sensation in those areas.

This anatomical specificity is why the choice relating to the membrane and skin of the nose is the correct answer. It is important in esthetic practice because understanding the sensory nerves involved can influence procedures that alter or affect these areas. Other options discuss different regions of the face and head but do not pertain directly to the infratrochlear nerve's primary functions or areas of influence.