Salivary gland. Artwork of a vertical, side section through the mouth showing the sublingual salivary gland (purple). The sublingual gland is situated directly below the tongue (not seen). Salivary glands secrete saliva, an alkaline fluid that moistens food, aids swallowing and contains enzymes which start the digestive process. The gland contains 2 types of secretory cell, serous and mucous secreting cells. Serous cells secrete watery serum and mucous cells secrete mucus. There are a pair of sublingual glands, one on either side of the mouth. Also seen are the teeth (with the incisors, grey, in section), gums, lips, hard palate (yellow, top) and soft palate (top right, red).