The salivary glands secrete saliva into the oral cavity of vertebrates, which moistens the mouth to help a person chew and swallow food. Enzymes contained in saliva could begin to digest part of the food. There are three pairs of major salivary glands opening into the mouth by well-developed ducts in human beings. Located between the ear and ascending branch of the lower jaw are the parotid glands, the largest of the three. The parotid gland is comprised of fat tissue and cells that produce mainly serous fluids. Submandibular glands are another pair of gland situated along the side of the lower jawbone. These glands are surrounded by a capsule of tissue and give off mixed secretions. The third pair is sublingual glands which rest on the floor of the mouth under the tongue. These glands secrete mixed fluids containing mainly mucus. Conditions like salivary atones or infections may interfere with the function of the salivary glands or block the ducts. A variety of target molecules on salivary tissues are used to detect associated disorders.