**Core Concept**
The endolymphatic duct is a crucial structure in the inner ear, playing a vital role in the regulation of endolymph pressure and the maintenance of balance. It is a part of the vestibular system, which is responsible for detecting changes in head position and movement.

**Why the Correct Answer is Right**
The endolymphatic duct connects the endolymphatic sac to the scala tympani of the cochlea. This connection allows for the drainage of excess endolymph from the scala media, which is essential for maintaining the proper ionic balance and preventing endolymphatic hydrops. The endolymphatic sac, located in the temporal bone, serves as a reservoir for endolymph and helps regulate its pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as the endolymphatic duct does not connect to the semicircular canals. The semicircular canals are part of the vestibular system, but they are not directly connected to the endolymphatic duct.

**Option B:** This option is incorrect as the endolymphatic duct does not connect to the cochlear aqueduct. The cochlear aqueduct is a separate structure that connects the scala tympani to the cerebrospinal fluid.

**Option C:** This option is incorrect as the endolymphatic duct does not connect to the saccule. The saccule is one of the otolith organs in the vestibular system, but it is not directly connected to the endolymphatic duct.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the endolymphatic duct plays a critical role in the pathogenesis of Meniere's disease, a disorder characterized by vertigo, tinnitus, hearing loss, and aural fullness. The endolymphatic duct's dysfunction can lead to the accumulation of excess endolymph, resulting in the characteristic symptoms of Meniere's disease.

**Correct Answer:** C.