Oral cavity is kept moist with the film of fluid called saliva. This saliva is released by numerous glands all around the oral cavity called salivary glands. Structurally, salivary glands have two components, the secreting end piece or the acini, which produces the saliva. And the duct system, which carries the saliva from the acini to the oral cavity. This makes their arrangement similar to a bunch of grapes. Salivary glands are exocrine, compound, tubulo-acinar, merocrine glands. Just to elaborate, salivary glands are not endocrine as they do not release their secretions directly into the bloodstream, but into the oral cavity via ducts therefore they are exocrine glands. Salivary glands are not simple glands as they do not have a single duct but multiple branches forming a duct system, making them a compound gland. Salivary glands are not tubular glands as the secretory part is not a tubule but an acini. However they are still not acinar glands but tubulo-acini glands, as this saliva secreted by the acini gets modified while passing through the ducts. Finally, during formation of saliva the cells of the acini do not degenerate, for the release of saliva, so they are not Holocrine glands, nor there is any loss of cytoplasm, so not Apocrine glands either. What happens is, that saliva is formed by secretary vesicles which are released by exocytosis with no loss of cytoplasm, making them merocrine glands. Classification of salivary glands can be done on the basis of size and on the basis of type of saliva that is secreted. On the basis of size, they are classified as major salivary glands and minor salivary glands. There are three pairs of major salivary glands, parotid gland, sub-mandibular gland and sublingual gland. Whereas minor salivary glands are numerous and named according to their location. Like labial gland, buccal gland, lingual gland, palatine gland, glossopalatine gland. Now on the basis of type of saliva, they are classified as serous salivary glands, which secrete watery saliva. Mucous salivary glands which secrete viscous saliva and mixed salivary glands which secrete a mixture of both. If we combine these two classifications, we see all major salivary glands secrete a different type of saliva. Parotid gland is a serous gland. Submandibular gland a mixed land and sublingual gland is mucous gland. Whereas in minor salivary glands, almost all are mucus in nature, except a lingual gland called von Ebner gland, which are serous glands. Similarly in the other classification, we see serous salivary glands are two, the parotid gland and von Ebner gland. Mix salivary gland, only the submandibular gland and mucous salivary glands are sublingual gland and all the minor salivary glands, except the von Ebner glands. Major salivary glands. The major salivary glands are comparatively bigger in size and their saliva reaches the oral cavity through long excretory ducts. They are covered by a fibrous capsule and in the oral cavity contribute about 95% of the total saliva. Let us start with the parotid gland. As the name suggests, it is located anterior to the external ear. It is superficial to the ramus and the masseter muscle. It is the largest major salivary gland, has a shape of a three-sided pyramid. Though the apex of this pyramid is downwards. Cranio-caudaly it measures 5.8 cm and ventro-dorsally it measures 3.4 cm. It weighs around 15 gm. Even though it is the largest gland, it contributes only 25% of the total saliva, which is serous in nature. The main excretory duct called the Parotid duct or Stenson's duct, is around 5 cm. It emerges from the middle of the anterior border, runs forward along the superficial surface of masseter and turns inward at its anterior border and crosses the buccinator muscle. It opens opposite the crown of the 2nd maxillary molar in the upper vestibule of the oral cavity. Sometimes a small salivary gland may be present in the middle of the duct called accessory parotid gland. Being the largest gland it has few structures running through it. Like the external carotid artery, enters the gland through the inferior surface and posteriorly gives off a branch called posterior auricular artery, anteriorly a branch called the maxillary artery and superiorly the superficial temporal artery. A vein enters the gland from the superficial surface, the superficial temporal vein, which joins a vein coming anteriorly, the maxillary vein and forms a vein called retromandibular vein. This vein then terminates into two divisions, anterior division and posterior division. Coming to the nerves. The 7th cranial nerve, facial nerve, enters the gland posteriorly and divides into 5 branches supplying the various facial muscles. Temporal, zygomatic, buccal, marginal mandibular and cervical. Submandibular gland. As the name suggests, it lies on the mesial aspect of the body of the mandible, in the submandibular triangle. It is the second largest salivary gland, having the size of a walnut and is roughly J-shaped, Weighing around 8 gm. The J-shape of the gland is because it gets indented by the posterior border of the mylohyoid muscle, which divides the gland into two lobes. The superficial lobe, below the mylohyoid muscle, which is bigger in size. And the deep lobe, above the mylohyoid muscle, which is smaller in size. Submandibular gland contributes 65% of the saliva, which is of mixed variety. Its main excretory duct emerges from the deep lobe of the gland, it is called the submandibular duct or the Wharton's duct. It is around 5 cm long and runs anteriorly and superiorly, opens into the floor of the mouth. In the oral cavity its opening is on the summit of the sublingual papilla, which is at the apex of a small swelling on either side of the lingual frenum. Sublingual gland. As the name suggests, it lies just beneath the tongue. It is the smallest major salivary gland. Has an almond shape and weighs just around 4 gm. The sublingual gland is located between the mucosa of the floor of the mouth above and mylohyoid muscle below. Sublingual gland contributes only 5% of the total saliva, which is of mucous nature. Sublingual gland has several small excretory ducts, around 15 in number, collectively called the ducts of Rivinus. They all open directly into the floor of the mouth. Bartholin's duct is its biggest excretory duct, which does not open in the oral cavity, but joins the wharton's duct coming from the submandibular gland. Minor salivary glands. Minor salivary glands are located just beneath the epithelium. They are small in size and have a small excretory duct. Unlike major salivary glands, fibrous capsule is not present. Minor salivary glands are present all over the oral cavity and are around 600 to 1000 in number. Collectively they produce only 5% of the total saliva and majority of them are mucous glands. They are named according to their anatomic location. Labial salivary glands present in the upper and lower labial mucosa. Buccal salivary glands present in the buccal mucosa. Glossopalatine glands present in the glossopalatine fold also called the anterior fossil pillar. Palatine glands present in the posterior lateral part of the hard palate, soft palate and uvula. Lingual glands can be classified into three groups, anterior lingual mucous glands also called the glands of Blandin and Nuhn, which are at the tip of the tongue. Posterior lingual mucous glands present in the posterior one third of the tongue and posterior lingual serous glands, also called the von Ebner glands, located adjacent the circumvalate papilla. von Ebner glands are the only minor salivary glands which are fully serous. Now why is that? One of the primary functions of saliva is lubrication of the oral cavity. For this to occur the saliva needs to form a thin layer or a film on the oral mucosa. This requires the saliva to be of thick consistency or higher viscosity like a lubricant in a machine. For this reason majority, of minor salivary glands present all over the oral cavity are mucus in nature. Now von Ebner glands, due to their location adjacent the circumvalate papillae, have a different function. Circumvalate papillae has taste buds on its lateral borders. So the food particle coming into the oral cavity has to enter the trough, so that the taste perception can take place. After that the food particle needs to be washed away by saliva back out of the circumvallate papillae. As another important function of saliva is cleansing. Now this flushing needs to be done by a watery saliva released by serous glands, which are von Ebner glands. In the oral cavity there are 3 areas where there are no minor salivary glands. Gingiva, anterolateral part of the palate and anterior two-thirds of the dorsum of the tongue.