The palatine glands form a continuous layer on the posterior surface of the mucous membrane of the soft palate and around the uvula. They are pure mucous glands.
Developmental The development of the palatine glands begins at approximately the 11th week of intrauterine life with the formation of solid epithelial buds arising from the basal layer of the palatal epithelium. These epithelial cords first appear at the junction of the hard and soft palates and initially develop in the lateral regions before progressing medially. Gland formation is symmetrical on both sides of the palate and does not occur along the midline. Following initial budding, the epithelial cords elongate into the underlying mesenchyme, become flask-shaped, and undergo branching morphogenesis. Canalization of the cords occurs during this period, leading to the formation of the primitive ductal system and early acinar differentiation. Between 14th and 20th weeks of intrauterine life, the secretory end pieces and duct system become increasingly differentiated. Mucous acini predominate, with occasional mixed or serous acini appearing. Cytochemical staining demonstrates PAS-positive, alcianophilic, and metachromatic material within the acini and ducts, indicating active mucin synthesis during this stage. As development progresses, the palatine glands exhibit characteristic histophysiological features, including increasing glandular complexity, maturation of mucous acini, and accumulation of secretory material within the ductal lumina. These findings suggest that functional mucin secretion by the palatine glands begins before birth and continues to mature throughout fetal development.
Anatomical structure According to Céspedes, the palatine salivary glands are made up of many tubuloacinar secretory endpieces, which are found within the lamina propria and are supported by dense connective tissue at 7 days after the baby's birth. These glands are mainly mucous, although some serous cells are also present showing a mixed secretory structure. The polarity of secretory cells is evident, with nuclei basally positioned and secretory granules predominantly in the apical cytoplasm. Two granules were identified: electron-lucent granules that reflect mucous secretion and electron-dense granules that represent serous secretion. In the cytoplasm there are elaborate organelles such as mitochondria as well as rough endoplasmic reticulum and Golgi apparatus, located mostly in the supranuclear region, indicating active secretory activity. Functional differentiation is suggested by myoepithelial cells which cover the basal part of the acini and are associated with microfilaments, mitochondria and Golgi apparatus. There are desmosomal junctions and membrane interdigitations between the secretory and myoepithelial cells. The glandular epithelium is separated from the connective tissue by a distinct basal lamina lined by layers of electron-dense and electron-lucent components. The SEM also reveals the three-dimensional arrangement of irregularly-shaped endpieces and the structural connective tissue framework. However, the glands at this stage are organized structurally and functionally active, with mucous secretion predominating. According to Mäkinen, the human palatine gland secretions (HPS) of adult patients were analyzed using direct samples from the palatal mucosa. This work aimed to characterize the chemical compounds and enzyme composition in these secretions, with comparison to mixed whole saliva samples. Palatine gland secretions from adult subjects contain high levels of glycoproteins and have been described in some papers by showing elevated levels of carbohydrates, hexosamines, and sialic acids. Such a feature is typical of mucin-rich secretions. In contrast to mixed saliva, palatine gland secretions lacked common salivary enzymes such as amylase, peroxidase, and lysozyme. However, they contained highly concentrated arylamidase enzymes. The conclusion drawn is that the secretion from palatine glands is chemically distinct from that of whole saliva and that palatine glands may have special biochemical functions, mainly on the basis of glycoprotein content and arylamidase activity.
Histology Palatine glands are minor salivary glands located under the mucous membrane non each side of the midline of the palate. Palatine glands have multiple histological features. The palatine glands are compound tubuloacinar minor salivary glands composed mainly of mucous-secreting acini. Being compound means they have a branched duct system, and tubuloacinar refers to the presence of both tubular and acinar secretory units. Histologically, the acini are predominantly mucous in nature, appearing pale with flattened basal nuclei due to mucin accumulation. Serous cells are few or absent, unlike the submandibular gland which is mixed but predominantly serous. Their mucous secretion primarily functions to lubricate the palatal mucosa during speech and swallowing. Palatine gland is divided into lobules by thin connective tissue septa that contain blood vessels, nerves, and small ducts. The secretory units consist predominantly of mucous acini, which appear large and pale or foamy in hematoxylin and eosin staining due to the presence of mucin droplets. The mucous cells are pyramidal with flattened, basally located nuclei and a relatively wide lumen. Serous cells are very few or absent, and serous demilunes are rarely seen, unlike in the Submandibular gland. Myoepithelial cells are present between the secretory cells and the basal lamina; these contractile cells assist in expelling the viscous secretion into the duct system. The duct system is relatively simple and poorly developed compared to major salivary glands, with short intercalated ducts, poorly developed or absent striated ducts, and short excretory ducts that open directly onto the palatal mucosal surface. The continuous production of thick mucous secretion functions to lubricate and protect the palatal mucosa during mastication, speech, and swallowing.
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