The mouth is the entrance to both the digestive and the respiratory systems. The inside of the mouth is lined with mucous membranes. When healthy, the lining of the mouth (oral mucosa) ranges in color from reddish pink to gradations of brown or black. The oral mucosa tends to be darker in dark-skinned individuals because their melanocytes (cells that produce melanin, a pigment that gives hair, skin, and eyes their color) are more active. The gums (gingivae) are usually paler by comparison and fit snugly around the teeth.