A patient presents with complete eyelid drop (ptosis). What muscle is primarily responsible for this condition?
Answer:
Levator palpebrae superioris.
Explanation:
The levator palpebrae superioris muscle originates from the roof of the orbit and inserts into the superior tarsus of the eyelid. It is innervated by the oculomotor nerve (CN III) and functions to elevate the upper eyelid. When there is loss of function in the levator palpebrae superioris, it results in complete ptosis.
Additionally, the superior tarsal muscle (Mueller’s muscle) is a collection of smooth muscle fibers that works alongside the levator palpebrae superioris, innervated by postganglionic sympathetic fibers from the superior cervical ganglion. While it aids in maintaining eyelid elevation, its loss of function leads to partial ptosis rather than complete ptosis.
