Final answer:
The Eustachian tube is the channel connecting the middle ear and the nasopharynx, essential for equalizing ear pressure and important for hearing and balance.
Step-by-step explanation:
The narrow channel that connects the middle ear and the nasopharynx is the Eustachian tube. This tube plays a key role in equalizing pressure between the middle ear and the external atmosphere, which helps to maintain balance and hearing function. The Eustachian tube opens into the nasopharynx, which is the upper part of the pharynx connected to the nasal cavities and provides a pathway for air during breathing and speech. The pharynx itself is divided into three regions: the nasopharynx, the oropharynx, and the laryngopharynx, with the nasopharynx being the most superior and involved only in breathing and speech.