Salivary gland, oral endocrine of human or vertebratesalivaGlands of.There are large and small salivary glands in the mouth.Small salivary glands scattered in each partoral cavityIn mucosa (such as lip gland, buccal gland, palate gland, tongue gland).The large salivary glands includeparotid gland、Submandibular glandandSublingual glandThree pairs, they are independent organs located around the mouth, but their ducts open in the oral mucosa.
It is the largest, slightly triangular wedge shaped, located at the front and bottom of the external auditory canal, on the surface of the rear of the masseter muscle, and the rear of the gland is particularly hypertrophic, reaching deep into the posterior mandibular fossa.The parotid duct is sent out from the front end of the gland near the upper edge, and moves forward through the surface of the masseter muscle at about a transverse finger below the zygomatic arch, bypasses the front edge of the masseter muscle, turns to the deep part, passes through the buccal muscle and opens to the buccal mucosa, forming a mucosal nipple at the opening, just opposite to the maxillary second molar.
Submandibular gland
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It is slightly oval, located in the lower mandibular triangle, between the mandibular body and hyoglossal muscle.The submandibular glandular duct originates from the inner surface of the gland, moves forward along the deep surface of the mucosa at the bottom of the mouth, and opens at the sublingual caruncle.
Sublingual gland
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Smallest, slender and slightly flat.It is located in the deep surface of the mucosa at the bottom of the mouth.There are about 5-15 small and large excretory tubes, which directly open to the mucosa at the bottom of the mouth;The other major duct often joins with the submandibular gland duct or opens separately in the sublingual caruncle.
The salivary glands secrete saliva, which can moisten the mouth and is conducive to swallowing and speaking.Human saliva contains amylase, which can preliminarily decompose starch in food.
Large salivary gland
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The great salivary gland has three pairs of parotid gland, submandibular gland and sublingual gland, and their ducts open in the mouth.
（1） General structure of salivary glands
The salivary gland is a compound tubular acinar gland with a thin capsule. The parenchyma of the gland is divided into many lobules, consisting of branched ducts and terminal acini.
1. Alveoli is the secretory part of the gland, which is in the form of vesicles or tubules and consists of a single layer of cubic or conical gland cells.There are myoepithelial cells between glandular cells and basement membrane, and between some duct epithelium and basement membrane. The cells are flat and have protrusions. The cytoplasm contains actin microfilaments.The contraction of myoepithelial cells contributes to the discharge of acinar secretions.There are three types of acini: serous, mucinous and mixed.
(1) Serous acinus: composed of serous gland cells.In HE staining sections, the cytoplasm was deeply stained.The basophilic cytoplasm at the base is strong, and there are many rough endoplasmic reticulum and ribosomes under the electron microscope.The nucleus is round and located at the base.There are many eosinophilic secretory granules (zymogen granules) in the top cytoplasm. The serous acinar secretion is thin and contains salivary amylase.
(2) Mucous alveolus: It is composed of mucous gland cells.In HE staining sections, the cytoplasm was slightly stained, and the secretory granules could not be displayed.The nucleus is oblate and occupies the bottom of the cell.Under the electron microscope, there are thick secretory granules (mucinogen granule) in the top cytoplasm.The secretion of mucinous acini is relatively thick, mainly mucus (glycoprotein).
(3) Mixed alveolus: composed of serous gonad cells and mucous gonad cells.The common form is that the acinus is mainly composed of mucous gonad cells, and several serous gonad cells are located at the bottom of the acinus or attached to the end of the acinus. They are arranged in a half moon shape in the section, so they are called demilune.The secretion of half a month can be released into the acinar cavity through the small tube between mucous cells.
2. The duct is a repeatedly branched epithelial duct, the excretory part of the gland, and its end is connected with the acinus.The salivary duct can be divided into the following sections:
(1) Intercalated duct: it is directly connected with the acinus, with a thin diameter and a single cuboidal or flat epithelium wall.
(2) Striated duct, or secretory duct, is connected with the intercalated duct. The diameter of the duct is the same. The wall of the duct is a single layer of high columnar epithelium. The nucleus is located at the top of the cell. The cytoplasm is eosinophilic.Vertical longitudinal lines can be seen at the cell base. Under the electron microscope, there are plasma membrane inner folds and mitochondria arranged in vertical rows. This structure increases the surface area of the cell base and facilitates the transport of water and electrolyte between cells and tissue fluid.The striated tube epithelial cells can actively absorb Na+in the secretion, discharge k+into the lumen, and can reabsorb or discharge water, so they can adjust the electrolyte content in saliva and the amount of saliva.
(3) Interlobular duct and common duct: striated ducts converge to form interlobular duct, which runs in interlobular connective tissue.The interlobular duct is thicker, and its wall is pseudostratified columnar epithelium.The interlobular ducts gradually converge and thicken, and finally form one or more common ducts opening in the mouth. The ducts near the mouth opening gradually become stratified squamous epithelium, which is continuous with the oral epithelium.
Carina salivary gland
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Carina salivary glandHidden in the upper part of the deep throat, it is located on a piece of cartilage called eustachian tube protuberance, with an average length of about 1.5 inches (3.9 cm).[1]
