Understanding the Anatomy
The upper and lower lips are the gateway to the rest of the oral cavity. They are responsible for protecting the mouth and for keeping food and drink in the mouth when you are eating or drinking. They also play a role in articulation (clear sounds) when you speak.
The upper lip extends from the bottom part of the nose, and the lower lip starts at the mental crease (top part of the jawbone). However, cancers that arise on the part of the upper and lower lips that look like facial skin are grouped in with skin cancer. Cancers on the pink part of the lips (mucosal lips) are grouped in with oral cavity cancers and will be discussed here.
The mucosal lip starts from the vermillion border (junction of facial skin with the pink lip) and ends at the point where the upper and lower lips meet when the mouth is closed.
On each side of the mouth is the commissure. This is where the upper and lower mucosal lips come together. Cancers in this part of the lip are very rare.
The mucosal lip is made up of squamous epithelium. There are several minor salivary glands under that layer. There is also a muscle layer. The upper and lower lips transition with the “labial mucosa,” which extends to the upper and lower gingiva (gums).