parotid gland parotid gland the parotid gland is a major salivary gland in many animals. in humans, the two parotid glands are present on either side of the mouth and in front of both ears. they are the largest of the salivary glands. each parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches. there are also two other types of salivary glands; they are submandibular and sublingual glands. sometimes accessory parotid glands are found close to the main parotid glands. "parotid" and "parotids" redirect here. for the carotids, see common carotid artery. parotid glandlocation of the left parotid gland in humans (shown in green).imagedetailspart ofsalivary glandssystemdigestive systemidentifierslatinglandula parotideameshd010306ta98a05.1.02.003ta22800fma59790anatomical terminology etymology the word parotid literally means "beside the ear". from greek παρωτίς (stem παρωτιδ-) : (gland) behind the ear < παρά - pará : in front, and οὖς - ous (stem ὠτ-, ōt-) : ear. structure the parotid glands are a pair of mainly serous salivary glands located below and in front of each ear canal, draining their secretions into the vestibule of the mouth through the parotid duct. each gland lies behind the mandibular ramus and in front of the mastoid process of the temporal bone. the gland can be felt on either side, by feeling in front of each ear, along the cheek, and below the angle of the mandible. the parotid duct, a long excretory duct, emerges from the front of each gland, superficial to the masseter muscle. the duct pierces the buccinator muscle, then opens into the mouth on the inner surface of the cheek, usually opposite the maxillary second molar. the parotid papilla is a small elevation of tissue that marks the opening of the parotid duct on the inner surface of the cheek. the gland has four surfaces – superficial or lateral, superior, anteromedial, and posteromedial. the gland has three borders – anterior, medial, and posterior. the parotid gland has two ends – superior end in the form of small superior surface and an inferior end (apex). a number of different structures pass through the gland. from lateral to medial, these are: facial nerve retromandibular vein external carotid artery superficial temporal artery branches of the great auricular nerve maxillary artery sometimes accessory parotid glands are found as an anatomic variation. these are close to the main glands and consist of ectopic salivary gland tissue. capsule of parotid gland capsule of the parotid gland is formed from the investing layer of the deep cervical fascia. it is supplied by great auricular nerve. the fascia splits to enclose the gland. this splitting occurs between the angle of the mandible and the mastoid process. the superficial lamina (parotidomassetric fascia) is thick and is attached to zygomatic arch. the deep lamina is thin and is attached to styloid process, tympanic plate and the ramus of the mandible. the part of deep lamina extending between the styloid process and the mandible is thickened to form stylomastoid ligament. the stylomandibular ligament separates parotid gland from the superficial lobe of the submandibular gland. location superficial or lateral relations: the gland is situated deep to the skin, superficial fascia, superficial lamina of investing layer of deep cervical fascia and great auricular nerve (anterior ramus of c2 and c3). anteromedial relations: the gland is situated posterolaterally to the mandibular ramus, masseter and medial pterygoid muscles. a part of the gland may extend between the ramus and medial pterygoid, as the pterygoid process. branches of facial nerve and parotid duct emerge through this surface. posteromedial relations: the gland is situated anterolaterally to mastoid process of temporal bone with its attached sternocleidomastoid and digastric muscles, styloid process of temporal bone with its three attached muscles (stylohyoid, stylopharyngeus, and styloglossus) and carotid sheath with its contained neurovasculature (internal carotid artery, internal jugular vein, and 9th, 10th, 11th, and 12th cranial nerves). medial relations: the parotid gland comes into contact with the superior pharyngeal constrictor muscle at the medial border, where the anteromedial and posteromedial surfaces meet. hence, a need exists to examine the fauces in parotitis. blood supply the external carotid artery and its terminal branches within the gland, namely, the superficial temporal and the maxillary artery, also the posterior auricular artery supply the parotid gland. venous return is to the retromandibular veins. lymphatic drainage the gland is mainly drained into the preauricular or parotid lymph nodes which ultimately drain to the deep cervical chain. nerve supply the parotid gland receives both sensory and autonomic innervation. general sensory innervation to the parotid gland, its sheath, and the overlying skin is provided by the auriculotemporal nerve. the autonomic innervation controls the rate of saliva production and is supplied by the glossopharyngeal nerve. the cell bodies of the preganglionic sympathetic fibres usually lie in the lateral horns of upper thoracic spinal segments (t1-t3). postganglionic sympathetic fibers from superior cervical sympathetic ganglion reach the gland as periarterial nerve plexuses around the external carotid artery and their function is mainly vasoconstriction. preganglionic parasympathetic fibers leave the brain stem from inferior salivatory nucleus in the glossopharyngeal nerve and then through its tympanic and then the lesser petrosal branch pass into the otic ganglion. there, they synapse with postganglionic fibers which reach the gland by hitch-hiking via the auriculotemporal nerve, a branch of the mandibular nerve.: 255 it is important to note that the terminal branches of the facial nerve arise in the parotid plexus from within the parotid gland. these nerves then merely pass through the parotid gland and do not innervate the gland itself. histology the parotid gland the gland has a capsule of its own of dense connective tissue but is also provided with a false capsule by the investing layer of the deep cervical fascia. the fascia at the imaginary line between the angle of the mandible and the mastoid process splits into a superficial and a deep lamina to enclose the gland. the risorius is a small muscle embedded with this capsule substance. the gland has short, striated ducts and long, intercalated ducts. the intercalated ducts are also numerous and lined with cuboidal epithelial cells and have lumina larger than those of the acini. the striated ducts are also numerous and consist of simple columnar epithelium, having striations that represent the infolded basal cell membranes and mitochondria.: 273 though the parotid gland is the largest, it provides only 25% of the total salivary volume. the serous cell predominates in the parotid, making the gland secrete a mainly serous secretory product. the parotid gland also secretes salivary alpha-amylase (saa), which is the first step in the decomposition of starches during mastication. it is the main exocrine gland to secrete this. it breaks down amylose (straight chain starch) and amylopectin (branched starch) by hydrolyzing alpha 1,4 bonds. additionally, the alpha amylase has been suggested to prevent bacterial attachment to oral surfaces and to enable bacterial clearance from the mouth. development the parotid salivary glands appear early in the sixth week of the prenatal development and are the first major salivary glands formed. the epithelial buds of these glands are located on the inner part of the cheek, near the labial commissures of the primitive mouth (from ectodermal lining near angles of the stomodeum in the 1st/2nd pharyngeal arches; the stomodeum itself is created from the rupturing of the oropharyngeal membrane at about 26 days.) these buds grow posteriorly toward the otic placodes of the ears and branch to form solid cords with rounded terminal ends near the developing facial nerve. later, at around 10 weeks of prenatal development, these cords are canalized and form ducts, with the largest becoming the parotid duct for the parotid gland. the rounded terminal ends of the cords form the acini of the glands. secretion by the parotid glands via the parotid duct begins at about 18 weeks of gestation. again, the supporting connective tissue of the gland develops from the surrounding mesenchyme. parotid gland swellings