The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva, which is formed of several things including amylase, a digestive enzyme that breaks down starch into maltose and glucose. In humans and some other mammals the secretion is alpha-amylase also known as ptyalin. Salivary glands produce saliva, which moistens the mouth to help a person chew and swallow food. Saliva also contains substances (enzymes) that begin the breakdown of food.
There are four pairs of salivary glands:
- ¬ The parotid glands are located between the ear and the jaw.
- ¬ The submandibular glands are located under the jaw.
- ¬ The sublingual glands are located on the floor of the mouth under the tongue.
- ¬ The buccal glands are not shown in this picture. They are located in the mucous membrane lining the cheeks and mouth. These glands produce only a small amount of saliva.
The two parotid glands are major salivary glands wrapped around the mandibular ramus in humans. The largest of the salivary glands, they secrete saliva to facilitate mastication and swallowing, and amylase to begin the digestion of starches. It is the serous type of gland which secretes the ptyalin. It enters the oral cavity via the parotid duct or Stensen duct. The glands are located posterior to the mandibular ramus and anterior to the mastoid process of the temporal bone. They are clinically relevant in dissections of facial nerve branches while exposing the different lobes of it since any iatrogenic lesion will result in either loss of action or strength of muscles involved in facial expression. They produce 20% of the total salivary content in the oral cavity.
The submandibular glands are a pair of major salivary glands located beneath the lower jaws, superior to the digastric muscles. The secretion produced is a mixture of both serous fluid and mucus, and enters the oral cavity via the submandibular duct or Wharton duct. Approximately 65-70% of saliva in the oral cavity is produced by the submandibular glands, even though they are much smaller than the parotid glands.You can usually feel this gland, as it is in the superficial cervical region and feels like a rounded ball. It is located about two fingers above the Adam's apple (laryngeal prominence) and about two inches apart under the chin.
The sublingual glands are a pair of major salivary glands located inferior to the tongue, anterior to the submandibular glands. The secretion produced is mainly mucous in nature, however it is categorized as a mixed gland. Unlike the other two major glands, the ductal system of the sublingual glands do not have intercalated ducts and usually do not have striated ducts either so they exit directly from 8-20 excretory ducts known as the Rivinus ducts. Approximately 5% of saliva entering the oral cavity comes from these glands.
Minor salivary glands:
There are 800-1000 minor salivary glands located throughout the oral cavity within the submucosa of the oral mucosa in the tissue of the buccal, labial, and lingual mucosa, the soft palate, the lateral parts of the hard palate, and the floor of the mouth or between muscle fibers of the tongue. They are 1-2mm in diameter and unlike the major glands, they are not encapsulated by connective tissue, only surrounded by it. The gland has usually a number of acini connected in a tiny lobule. A minor salivary gland may have a common excretory duct with another gland, or may have its own excretory duct. Their secretion is mainly mucous in nature (except for Von Ebner glands- see next section) and have many functions such as coating the oral cavity with saliva. Problems with dentures are sometimes associated with minor salivary glands if there is dry mouth present (see further discussion). The minor salivary glands are innervated by the seventh cranial or facial nerve.
Von Ebner's glands:
Von Ebner's glands are glands found in a trough circling the circumvallate papillae on the dorsal surface of the tongue near the terminal sulcus. They secrete a purely serous fluid that begins lipid hydrolysis. They also facilitate the perception of taste through secretion of digestive enzymes and proteins. The arrangement of these glands around the circumvallate papillae provides a continuous flow of fluid over great number of taste bud along the sides of the papillae. It is important for dissolving the food particles to be tested.