The parotid gland, the largest of the salivary glands, weighs approximately 15–30 g and is 6 × 4 cm in dimensions. The parotid gland is located bilaterally on each side of the face in front of the ears and extends to the lower borders of the mandible. Each gland is covered by fibrous connective tissue capsule that secretes serous fluid, a watery and protein-rich solution. The parotid gland is shaped like an inverted pyramid. It is positioned inferior to the zygomatic arch, anteroinferior to the external acoustic meatus, anterior to the mastoid process, and posterior to the ramus of the mandible (Fig. 1.2). The gland is divided into a base, an apex, and lateral, anterior, and posterior surfaces. Its laterosurface is situated right below the skin and superficial fascia of the head. The anterior surface of the gland is grooved by the ramus of the mandible and masseter muscle (from this depression the maxillary artery leaves the gland). The posterior surface is grooved by the mastoid process, the sternocleidomastoid muscle, and styloid process. From this site, the external carotid and the facial nerve enter the gland. The apex of the gland is located between the angle of the mandible and the sternocleidomastoid muscle. From this area, the retromandibular vein and the facial nerve leave the gland [12] (Fig. 1.2).

The parotid gland has a large duct (Stensen’s duct) that crosses the masseter muscle and opens near the upper second molar in the oral cavity (Fig. 1.3). Blood supply is provided by the terminal branches of external carotid artery (ECA). The facial nerve and its branches form an important landmark, dividing the parotid into superficial and deep lobes. The main sensory nerve within this gland is the auriculotemporal nerve (Fig. 1.2). Secretomotor supply to the parotid is derived from the glossopharyngeal nerve (IX), via the tympanic branch, tympanic plexus, lesser petrosal nerve, and the pterygopalatine ganglion. The parotid contains superficial lymph nodes in its superior lobe. These nodes drain deeply to the deep cervical nodes or superficially to the superficial cervical nodes [6].

The submandibular gland is approximately half of the weight (7–10 g) and size (4–5 cm) of the parotid gland. This gland is also encapsulated, but there is no fibrous connective tissue. The submandibular gland is located in the submandibular triangle formed by the anterior and posterior bellies of the digastric muscle and the inferior margin of the mandible (Fig. 1.1b). The gland present three surfaces: lateral (connected to medial surface of the mandible), medial (connected to the mylohyoid, hyoglossus, and digastric muscles), and inferior (shielded by the skin and platysma muscle). The gland is divided into superficial and deep lobes, the latter being the majority part of the gland. The deep lobe projects from the mylohyoid and hyoglossus muscles. The submandibular duct, also referred to as Wharton’s duct, exits from the deep part of the gland adjacent to the mandibular second molar and ascends anteriorly to the floor of the mouth (Fig. 1.4). As the duct exits the gland, it lies inferior to the lingual nerve. The blood supply originates from the facial and lingual artery and submental and facial veins. The innervation of this gland relies on submandibular ganglion and lingual nerve located superiorly to the deep process of the gland (Fig. 1.1) [2, 6, 12].

The sublingual gland is the smallest of the major salivary glands. It is almond shaped and is located underneath the mucous membrane of the floor of the mouth between the mandible and genioglossus muscle (Fig. 1.1c). The sublingual gland is not covered by a fascial capsule. This gland has approximately 8–20 small ducts (the ducts of Rivinus), which exit the superior aspect of the gland and open along the sublingual fold on the floor of the mouth. Occasionally, several of these ducts may join to form a common duct (the duct of Bartholin), which typically empties into the Wharton’s duct. The secretions from sublingual and submandibular glands flow through this duct and excrete into the floor of the mouth below the tongue. The sublingual and submental arteries are the main source of circulation in this salivary gland. The lingual, the chorda tympani, and the sympathetic nerves are responsible for its innervation (Fig. 1.1) [2, 6, 12].

The minor salivary glands are widely distributed throughout the oral mucosa, palate, uvula, floor of the mouth, posterior tongue, retromolar and peritonsillar area, pharynx, larynx, and paranasal sinuses. There are hundreds (600–1,000) of these small glands ranging in size from 1 to 5 mm (Fig. 1.5). Unlike the major glands, the minor glands present a single duct that secretes directly into the oral cavity. These glands can secrete serous, mucous, or mixed saliva. Additionally, minor salivary glands may be found at the superior pole of the tonsils (Weber’s glands) and at the base of the tongue (von Ebner’s glands). Parasympathetic innervation is derived from the lingual nerve, except for the minor glands of the palate, which receive their parasympathetic fibers from the palatine nerves, fed by the sphenopalatine ganglion.

In parotid glands, secretory end pieces present themselves as an encapsulated spherical structure with 8–12 of only serous cells (Fig. 1.9). Each of these cells is pyramidal in shape: the broad base is adjacent to the connective tissue called stroma, while its narrow apex faces the central lumen (Fig. 1.9). The submandibular gland has similar secretory end pieces; however, it contains both mucous- and serous-secreting cells (Fig. 1.10). Mucous cells form the main lining of these submandibular gland secretory acini, while a group of serous-secreting cells lie on the periphery and are referred to as serous demilune (Fig. 1.11) [5, 6].