Salivary Gland PDF

Salivary Gland Dr /Abdel-latif Galal Lecturer of oral Medicine& Periodontology Introduction The salivary glands are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds...

Salivary Gland Dr /Abdel-latif Galal Lecturer of oral Medicine& Periodontology Introduction The salivary glands are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous, or seromucous (mixed). in serous secretions, the main type of protein secreted is alpha- amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions, the main protein secreted is mucin, which acts as a lubricant.  In humans, between 0.5 and 1.5 l of saliva are produced every day.  Classification of Glands Serous Gland- thin, watery secretion rich in enzymes e.g. Parotid gland Mucous Gland- thick, viscous secretion for protection and lubrication. e.g. Sublingual salivary gland Mixed Gland (seromucous)- both watery and viscous material.e.g. Submandibular salivary gland Histology of Salivary glands Both major and minor S.G. composed of parenchyma elements are derived from oral epith. and consists of secretary end piece or acini and these secretary units leading into ducts that open into oral cavity. The connective tissue (C.T.) forms a capsule around the gland and extends into it, dividing groups of secretary units and ducts into lobes and lobules The major salivary glands Parotid gland The two parotid glands are major salivary glands wrapped around the mandibular ramus in humans. These are largest of the salivary glands, secreting saliva to facilitate mastication and swallowing, and amylase to begin the digestion of starches. It is the serous type of gland which secretes alpha-amylase. It enters the oral cavity via the parotid duct (stensens duct) opposite to second molar. They produce 20% of the total salivary content in the oral cavity. Mumps is a viral infection, caused by infection in the parotid gland. Parotid Gland Parotid Gland Submandibular glands The submandibular glands (previously known as submaxillary 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. Around 70% of saliva in the oral cavity is produced by the submandibular glands, they are much smaller than the parotid glands. Submandibular Gland Submandibular Gland 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. About 5% of saliva entering the oral cavity comes from these glands. Sublingual-purely mucous gland Minor salivary glands Around 800 to 1,000 minor salivary glands are located throughout the oral cavity 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 They are 1 to 2 mm in diameter and unlike the major glands, they are not encapsulated by connective tissue, only surrounded by it Their secretion is mainly mucous in nature and have many functions such as coating the oral cavity with saliva.  Minor salivary glands of Palate Aggregations of Mucous acini No striated duct Ducts Intercalated Ducts The primary saliva produced by the secretory end pieces passes first through the intercalated ducts The intercalated ducts are lined by a simple cuboidal epithelium. The overall diameter of the intercalated ducts is smaller than that of the end pieces, and their lumina are larger than those of the end pieces Striated Ducts The striated ducts, which receive the primary saliva from the intercalated ducts, constitute the largest portion of the duct system. These ducts are located within the lobules of the gland, that is, intralobular. Striated duct cells are columnar, with a centrally placed nucleus and pale, acidophilic cytoplasm. Ducts Striated Duct Excretory Ducts The excretory ducts are located in the connective tissue septa between the lobules of the gland, that is, in an extralobular or interlobular location. These ducts are larger in diameter than striated ducts and typically have a pseudostratified epithelium with columnar cells. End piece of salivary gland The functional unit of the salivary glands is the terminal secretory piece called acini with a roughly spherical or tubular shape. It also consists of branched ducts for the passage of the saliva and also plays an important role in the production and modification of saliva. Similarities Between Serous and Mucous Serous and mucous are two types of glands, which make up the salivary glands. Both are exocrine glands, stimulated by the parasympathetic nervous system. Secretions of both glands are involved in lubrication, solubilizing dry food, and oral hygiene. Difference between Serous & Mucous Acini Serous Mucous Thin, watery Thick, viscous Proteinaceous secretion Mucopolysaccharides Central rounded Nucleus Nucleus-flat & peripheral Small Lumen Large Lumen Indistinct cell bondaries Distinct cell boundaries Darkly stained Lightly stained Enzymatic action Protection & lubrication Parotid Gland Sublingual gland Myoepithelial cells: They are contractile cells (contain the contractile filaments actin and myosin).They have many similarities to smooth muscle but are derived from epith. These cells are present around the secretary acini and have stellate shape. Their appearance is resemble the basket cradling the secretary units. Contraction of these cells is thought to provide support for the acini and intercalated ducts during active secretion of saliva. Mixed Salivary Gland Function Protection: Saliva consists of proteins (for example; mucins) that lubricate and protect both the soft and hard tissues of the oral cavity. Buffering: In general, the higher the saliva flow rate, the faster the clearance and the higher the buffer capacity, hence better protection from dental caries. Pellicle formation: Saliva forms a pellicle on the surface of the tooth to prevent wearing. Digestion: Saliva contains amylase, which hydrolyses starch into glucose, maltose, and dextrin. Antimicrobial action: Saliva can prevent microbial growth based on the elements it contains.