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Chapter 1 Surgical Anatomy, Embryology, and Physiology of the Salivary Glands
John D. Langdon, FKC, MB BS, BDS, MDS, FDSRCS, FRCS, FMedSci
Emeritus Professor of Maxillofacial Surgery King’s College London, England
Outline
Parotid Gland Embryology Anatomy Contents of the Parotid Gland Facial Nerve Auriculotemporal Nerve Retromandibular Vein External Carotid Artery Parotid Lymph Nodes Parotid Duct Nerve Supply to the Parotid
Submandibular Gland Embryology Anatomy Superficial Lobe Deep Lobe Submandibular Duct Blood Supply and Lymphatic Drainage Nerve Supply to the Submandibular Gland Parasympathetic innervation Sympathetic innervation Sensory innervation
Sublingual Gland Embryology Anatomy Sublingual Ducts Blood Supply, Innervations, and Lymphatic Drainage
Histology of the Salivary Glands
Case Presentation – Wait, What?
Introduction
There are three pairs of major salivary glands consisting of the parotid, submandibular, and sublingual glands. In addition, there are numerous minor glands distributed throughout the oral cavity within the mucosa and submucosa.
On average, about 1.5 l of saliva are produced each day but the rate varies throughout the day. At rest, about 0.3 ml/min is produced but this rises to 2.0 ml/min with stimulation. The contribution from each gland also varies. At rest, the parotid produces 20%, the submandibular gland 65%, and the sublingual and minor glands 15%. On stimulation, the parotid secretion rises to 50%. The nature of the secretion also varies from gland to gland. Parotid secretions are almost exclusively serous, the submandibular secretions are mixed, and the sublingual and minor gland secretions are predominantly mucinous.
Saliva is essential for mucosal lubrication, speech, and swallowing. It also performs an essential buffering role that influences demineralization of teeth as part of the carious process. When there is a marked deficiency in saliva production, xerostomia, rampant caries, and destructive periodontal disease ensues. Various digestive enzymes – salivary amylase – and antimicrobial agents – IgA, lysozyme, and lactoferrin – are also secreted with the saliva.
Parotid Gland
EMBRYOLOGY
The parotid glands develop as a thickening of the epithelium in the cheek of the oral cavity in the 15 mm Crown Rump length embryo (sixth week of intrauterine life) (Zhang et al. 2010; Berta et al. 2013; Chadi et al. 2017). This thickening extends backward toward the ear in a plane superficial to the developing facial nerve. The deep aspect of the developing parotid gland produces bud‐like projections between the branches of the facial nerve in the third month of intrauterine life. These projections then merge to form the deep lobe of the parotid gland. By the sixth