Which salivary gland is located inferior to the jaw

The salivary glands consist of a series of branched ducts which terminate in a spherical or tubular endpieces or acini; a correlation can be made to a bunch of grapes, with the stems analogous to the ducts and the grapes indicating the secretory endpieces. Serous and mucous cells Figure 1 are the two main types of secretory cells present in salivary gland and divided into two main groups.

The major salivary glands include the paired parotid, submandibular, and sublingual glands. Additionally, the mucosa of the upper aerodigestive tract is lined by hundreds of small, minor salivary glands. The connective tissue forms a capsule around the gland and extends into it, dividing groups of secretory units and ducts into lobes and lobules.

Blood vessels, lymphatic vessels and nerves that supply the gland, are present within the capsule [ 1 ]. Structural organization of salivary gland [ 3 ]. The salivary glands are compound glands as they have more than one tubule entering the main duct, and the architectural arrangement is tubuloacinar, where acini are secretory units.

These secretory units are merocrine as they release only the secretion of the cell from the secreting units. Myoepithelial cells are contractile cells associated with the secretory endpieces and intercalated ducts of the salivary gland [ 2 ]. On the basis of size and location, salivary glands are classified as [ 1 , 2 ]:. On the basis of secretion [ 3 ], they are classified as:.

These are the largest, bilaterally paired, and situated extraorally, but their secretion reaches the oral cavity by variable long ducts. The parotid gland is the largest of all the salivary glands and weighs about 15—30 g. It is located below the external acoustic meatus between the ramus of the mandible and the sternocleidomastoid.

It is divided by facial nerve into a superficial and deep lobe. The superficial lobe, overlying the lateral surface of the masseter, is defined as the part of the gland lateral to the facial nerve. The deep lobe is medial to the facial nerve and located between the mastoid process of the temporal bone and the ramus of the mandible.

An accessory parotid gland may also be present lying anteriorly over the masseter muscle between the parotid duct and zygomatic arch [ 4 ]. It is the second largest salivary gland, also known as submaxillary salivary gland, weighs about 7—16 g and is almost the size of a walnut. It is situated in the submandibular triangle, which has a superior boundary formed by the inferior edge of the mandible and inferior boundaries formed by the anterior and posterior bellies of the digastric muscle.

The gland is approximately J-shaped being indented by the posterior border of the mylohyoid which divides into a larger part superficial to the muscle and a smaller part lying deep to the muscle [ 4 ].

The duct opens on the floor of the mouth, on the summit of the sublingual papilla also called the caruncula sublingualis, lateral to the lingual frenulum [ 2 ]. It is the smallest of all the three major salivary glands that is almond shaped and weighs about 3—4 g.

The gland lies above the mylohyoid, below the mucosa of the floor of the mouth, medial to the sublingual fossa of the mandible, and lateral to the genioglossus [ 4 ]. It comprises of one main gland duct with various small ducts. Several smaller ducts, duct of Rivinus, open independently along the sublingual fold [ 2 ]. The minor salivary glands are placed below the epithelium in almost all parts of the oral cavity. These glands comprise numerous small groups of secretory units opening via short ducts directly into the mouth.

They lack a distinct capsule, instead mixing with the connective tissue of the submucosa or muscle fibers of the tongue or cheeks [ 2 ]. These glands are present on the lips and cheeks and comprise of mucous tubules with serous demilunes [ 1 , 2 ]. These are located to the region of the isthmus in the glossopalatine fold but may extend from the posterior extension of the sublingual gland to the glands of the soft palate [ 1 , 2 ].

These are located in the glandular aggregates present in the lamina propria of the posterolateral aspect of the hard palate and in the submucosa of the soft palate and uvula [ 1 , 2 ]. The glands of the tongue can be divided into various groups [ 1 , 2 ]. The anterior lingual glands glands of Blandin and Nuhn are present near the apex of the tongue. The ducts open on the ventral surface of the tongue near the lingual frenulum. The posterior lingual mucous glands are present lateral and posterior to vallate papillae and in association with lingual tonsil.

The ducts of these glands open on the dorsal surface of the tongue. The development of the glandular tissue involves the interaction of the epithelium with the underlying mesenchyme to form the functional part of the tissue [ 5 , 6 ].

These epithelial-mesenchymal interactions are also known as secondary induction in which the mesenchyme is in close proximity with the epithelium and is required for the normal development of the epithelium. For example, epithelial-mesenchymal interactions regulate both the initiation and growth of the glandular tissue and the eventual cytodifferentiation of cells within the salivary glands.

The mesenchyme, therefore, is required for normal development as well as formation of the supporting part of the adult gland. All salivary glands follow a similar development pattern. The functional glandular tissue parenchyma develops as an epithelial outgrowth glandular bud of the buccal epithelium that invades the underlying mesenchyme. The connective tissue stroma capsule and septa and blood vessels form from the mesenchyme. The mesenchyme is composed of cells derived from neural crest and is important for the normal differentiation of the salivary glands.

As the bud formation begins during development, the portion of the bud closest to the stomodeum eventually differentiates into the main excretory duct of the gland, while the most distal portion of the bud forms the secretory endpieces or acini. The origin of the epithelial buds is believed to be ectodermal in the parotid and minor salivary glands but endodermal in origin in the submandibular and sublingual glands.

The parotid gland originates near the corners of the primitive oral cavity by the sixth week of prenatal life. The submandibular glands arise from the floor of the mouth at the end of the sixth or the beginning of the seventh week in utero. The sublingual gland forms lateral to the submandibular primordium at about eighth week. All the minor salivary glands bud from buccal epithelium but start after their 12th prenatal week. Stages of development [ 5 , 6 ] Bud formation, i.

Formation and growth of epithelial cord: A solid cord of cells forms from the epithelial bud through cell proliferation. Condensation and proliferation occur in the surrounding mesenchyme which is closely associated with the epithelial cord. The basal lamina plays a role in influencing morphogenesis and differentiation of the salivary glands throughout the development.

Initiation of branching in terminal parts of epithelial cord and continuation of glandular differentiation: The epithelial cord proliferates rapidly and branches into terminal bulbs. Dichotomous branching of epithelial cord and lobule formation: The branching continues at the terminal portion of the cord forming an extension treelike system of bulbs. As branching occurs, the connective tissue differentiates around the branches, eventually producing extensive lobulation.

The glandular capsule forms from mesenchyme and surrounds the entire glandular parenchyma. Canalization of presumptive ducts: Canalization of the epithelial cord, with the formation of a hollow tube or duct, usually occurs by the sixth month in all the major salivary glands. Different rates of cell proliferation between the outer and inner layers of the epithelial cord.

Fluid secretion by the duct cells which increases the hydrostatic pressure and produces a lumen within the cord. Further branching of the duct and structure and growth of the connective tissue septa continues at this stage of development. Cytodifferentiation: The final stage of salivary gland development is the histodifferentiation of the functional acini and intercalated ducts. Myoepithelial cells arise from the epithelial stem cells in the terminal tubules and develop in concert with acinar cytodifferentiation.

Parasympathetic nerves play an important role in epithelial tubulogenesis in the developing salivary gland which involve epithelial-mesenchymal interaction. The neurotransmitter, i. Neurotrophic factor neurturin NRTN , secreted by the buds, binds its receptor GFR alpha 2 and promotes functional nerve outgrowths to ensure parallel development of nerves and epithelium. Cystic fibrosis transmembrane conductance regulator CFTR causes lumen expansion during development [ 7 ].

The functional unit of a salivary gland is the terminal secretory unit called acini [ 1 , 2 ]. Regardless of size and location, the terminal secretory unit is made up of epithelial secretory cells, namely, serous and mucous acini. The serous and mucous cells along with myoepithelial cells are arranged in an acinus or acini with a roughly spherical or tubular shape and a central lumen.

Serous cells : They are pyramidal in shape with a broad base on the basement membrane, and the apex faces the lumen. The serous cells have a spherical nucleus placed at the basal region of the cell along with numerous secretory granules in which macromolecule components of saliva are stored and are present in the apical cytoplasm.

The granules are zymogen granules and are formed by glycosylated proteins which are released into a vacuole. The serous cells show acid phosphates, esterases, glucuronidase, glucosidase, and galactoside activity. The central lumen usually has fingerlike extensions located between adjacent cells called intercellular canaliculi that increase the size of the luminal surface of the cells [ 2 ].

Mucous cells : The secretory endpieces that are composed of mucous cells typically have a tubular configuration; when cut in cross section, these tubules appear as round profiles with mucous cells surrounding central lumen of larger size than that of serous endpieces. The nucleus is oval or flattened in shape and located above the basal plasma membrane.

Sometimes, mucous cells have bonnet- or crescent-shaped appearance, which is made up of serous cells and are also known as demilunes first described by Giuseppe Oronzo Giannuzzi in The presence of demilunes is not clearly known, but these demilunes occur as a result of artifact during tissue preparation. Nowadays, recent studies like rapid freezing, freeze substitution, and three-dimensional reconstruction techniques have shown that serous cells align with mucous cells to surround a common lumen.

The mucous cells show accumulation of large amounts of secretory product that pushes the nucleus and endoplasmic reticulum against the basal cell membrane. The mucous secretion differs from secretion of serous in two important aspects: The secretion of mucous cells has little or no enzymatic activity and is responsible mainly for lubrication and protection of the oral tissues.

The ratio of carbohydrates to protein is greater, and large amount of sialic acid and occasionally sulfated sugars are present [ 2 ]. In routine histological sections, the secretion of mucous cell appears unstained, and they are strongly stained when special stains like PAS, alcian blue, mucicarmine, etc.

These are the contractile cells associated with secretory endpiece and intercalated duct of the salivary glands. These cells are present between the basal lamina and the secretory or duct cells and are joined to the cells by desmosomes. They appear similar to smooth muscle but are derived from the epithelium. They are also known as basket cells or octopus sitting on a rock. The myoepithelial cells located around the secretory endpieces have stellate-shaped, numerous branching processes with a flattened nucleus and scanty perinuclear cytoplasm, but the cells associated with intercalated ducts have more fusiform shape and are elongated with fewer processes.

These cells accelerate the initial flow of saliva from the acini, reduce luminal volume, support the underlying parenchyma, reduce the back permeation of fluid, and also help to maintain the patency. They maintain the cell polarity and structural organization of cells. They secrete various tumor suppressor proteins such as protease inhibitors and antiangiogenesis factors which provide a barrier against invasive epithelial neoplasm. It consists of hollow tubes that connect initially with the acinus, i.

It is not a pipeline or conduit for the passageway for the saliva, but it actively participates in the production and modification of saliva. On the basis of location, ducts are of two types: Intralobular ducts : Those ducts which are within the lobule. The intercalated and striated ducts are intralobular ducts. Interlobular ducts : Those ducts which lie within the connective tissue within the lobules of the gland. The excretory ducts are interlobular ducts.

These are lined by single layer of cuboidal epithelium and are surrounded by myoepithelial cell bodies, and their processes typically are found along the basal surface of the duct. Under the light microscope, the intercalated ducts are difficult to identify as they are compressed between the secretory units.

Under the electron microscope, the intercalated ducts have centrally placed nuclei and a small amount of cytoplasm containing some rough endoplasmic reticulum and a small Golgi complex.

A few secretory granules may be found in the apical cytoplasm, especially in the cells located near the endpieces. The apical cell surface has a few short microvilli projecting into the lumen, and lateral surfaces are joined by junctional complexes. The macromolecule components, i. The striated ducts receive the primary saliva from the intercalated ducts which constitute the largest portion of the duct system and are lined by columnar cells with a centrally placed large, spherical nucleus and pale, acidophilic cytoplasm.

Under the electron microscope, the basal cytoplasm of the striated duct cells is partitioned by deep infoldings of the plasma membrane producing numerous sheetlike folds that extend beyond the lateral boundaries of the cell and interdigitate with similar folds of adjacent cells.

Between the membrane infoldings, a large amount of radially oriented mitochondria are located in the portion of the cytoplasm. The combination of infoldings and mitochondria accounts for the striations seen in the light microscope.

Obstruction of the ducts, which can happen because of salivary stones or narrowing of the duct from infection, can cause the saliva to back up into the gland and lead to it to swelling up as well.

If you would like to know more about the salivary glands, schedule a consultation with parotid surgeon Dr. Larian today by calling At the Center for Advanced Parotid Surgery, our team of medical professionals specializes in performing minimally invasive parotidectomy with a focus on facial nerve preservation and facial reconstruction.

It really depends upon exactly what was done during the surgery. In most cases, a brief hospital stay of four days or less may be required. In many cases, yes. In fact, it is often safer to do the surgeries concurrently because the parotid surgical procedure carefully traces the facial nerve and positions it safely.

Doing a facelift at the same time lowers the chance of accidentally damaging this nerve at a later time because of its shifted position. Depending on the size of the tumor removed, there may be excess skin on one side of the face that will need to be tightened. To maintain facial symmetry, the other side of the face may also need tightening. So a facelift at this time may be an ideal choice. Larian and his team will advice you if a facelift is an option for you.

The most common approach to dealing with parotid tumors, even benign ones, is to surgically remove them. These tumors can grow to abnormal sizes that can disfigure the face. More importantly, even a benign parotid tumor can become cancerous if left alone to grow.

There are a number of non-surgical procedures that often help the stones go away without surgery. You can plan on one to two weeks for initial incision healing and about six weeks for complete incision healing. Scar creams are advised for use to hasten healing and should be used for the first six weeks. Incisions may continue to change in form for up to two years after surgery, but most scars are hidden behind the jawline and ear and not readily noticeable.

Frequently Asked Questions about Parotid Surgery: At the Center for Advanced Parotid Surgery, our team of medical professionals specializes in performing minimally invasive parotidectomy with a focus on facial nerve preservation and facial reconstruction. How Should I Prepare for Surgery? Ensure all your questions are answered. Write them down when you think of them. You should have a clear idea of exactly what surgery is planned, what will be done, the risks, all your options and what the expected benefits are.

You should tell your surgeon what medications and supplements including herbal and OTC medications like ibuprofen you are currently taking. Ensure that you have stopped taking any medication or supplement that our surgeon asks within the proper timeframe. If you are not already leading a healthy life, it is best to start doing so several weeks before the surgery, not just before. Be active, eat healthy and quit smoking if you smoke.

How long does Parotid surgery take? Most parotidectomies take between 3 and 4 hours. Do salivary gland stones go away on their own? How long does it take for a Parotidectomy to heal?