Where does the parotid duct open into the mouth?

The parotid duct, also known as Stensen's duct, is responsible for draining saliva from the parotid gland, which is one of the major salivary glands. The correct location where the parotid duct opens into the mouth is opposite the maxillary second molar.

This opening is situated on the buccal mucosa, which is the lining inside the cheeks, and is often marked by a small elevation called the parotid papilla. The positioning of the duct allows saliva to enter the oral cavity directly where it is needed for the initial stages of digestion, especially during chewing.

The other locations described in the options do not accurately reflect where the duct opens. The area near the incisors and beneath the tongue pertains to different anatomical structures, such as the submandibular and sublingual glands. Additionally, while adjacent to the molar region may imply a proximity, it does not accurately specify the precise anatomical landmark of the maxillary second molar where the duct actually opens. Thus, identifying the correct opening location of the parotid duct is critical for understanding salivary gland function and oral anatomy.