Answer
The cheeks and the lips form the lateral and ventral borders (respectively) of the oral cavity. These structures are described as fleshy, because they include muscles-- the obicularis oris of the lips, and the buccinator muscle of the cheeks. Also contributing to this fleshiness, and underlying these muscles is a layer of subcutaneous fatty tissue. Other features of these organs are the labial frenulum, which is a fold of tissue which attaches each lip to the gingiva ; the vestibule is the space between lips or cheek and the teeth.
Work Step by Step
The lips have three anatomical regions: the cutaneous area, the red area, and the labial mucosa:
The cutaneous area has hair follicles and sebaceous glands, and may grow a mustache on the upper lip region. It has the same hue as the rest of the face.
The hairless region, where the lips meet, usually, has a red or vermillion color. The dermal papillae in this region grow tall ; this permits blood capillaries and nerves to approach close to the surface of the lips. This is responsible for the fine sensitivity, as well as the deep reddish color of this area.
The third region of the lips is the labial mucosa. It is the inner surface of the lip adjacent to teeth and gingiva.
