When you insert your finger into your ear, you hit a dead end. You can't insert your finger into the auditory canal. What's this dead end called, the medical term for it?
There is no dead end from the entrance of the auditory canal to the tympanic membrane. The diameter and shape of the object inserted rather determine whether it can reach deep enough.
The above statement can be proved by following examples:
ENT doctors use an otoscope on a regular basis to directly examine the tympanic membrane (eardrum), meaning the emitted light entering the meatus from the otoscope, and the reflected light from the tympanic membrane exiting the auditory meatus are following straight paths.
Another practical example is the use of tympanic temperature to quickly measure core temperature. Again, the infrared light emitted by the tympanic membrane has to follow a straight path out of the meatus, otherwise it would be absorbed.
Lastly, see below picture that graphically shows the relative straightness of the meatus. There is some curvature, but certainly no dead end. A dead end, or hooked region with a sharp angle would be disastrous for hearing sensitivity, as it would block the passage of sound waves to the middle ear.
structures of the ear. source: WebMD.
The finger is simply too wide to enter the meatus to the tympanic membrane. In contrast, cotton buds do readily enter the meatus up until the tympanic membrane and ENT doctors sadly see quite a lot of cases where folks turn in with ruptured tympanic membranes due to excessively deep insertions of cotton buds.