Salivary Gland Pathology

Diagnosis and Management

Eric R. Carlson, Robert A. Ord

• Publisher: Wiley-Blackwell
• Year: 2015
• ISBN:
  9781118949122
• Edition: 2
• Topic: Medicina
• Subtopic: Cirugía y medicina quirúrgica

Salivary Gland Pathology: Diagnosis and Management, Second Edition, updates the landmark text in this important discipline within oral and maxillofacial surgery, otolaryngology/head and neck surgery, and general surgery. Written by well-established clinicians, educators, and researchers in oral and maxillofacial surgery, this book brings together information on the etiology, diagnosis, and treatment of all types of salivary gland pathology. Clear and comprehensive, Salivary Gland Pathology: Diagnosis and Management offers complete explanation of all points, supported by a wealth of clinical and surgical illustrations to allow the reader to gain insight into every facet of each pathologic entity and its diagnosis and treatment. Salivary Gland Pathology: Diagnosis and Management offers comprehensive coverage of all aspects of this topic. Beginning with the embryology, anatomy and physiology of the salivary glands, the first section of the book discusses radiographic imaging, infections, cystic conditions, sialoadenitis and sialolithiasis, and systemic diseases. The second section of the book is devoted to the classification of salivary gland tumors and devotes individual chapters to the discussion of each type. Additions for this section of the second edition include molecular biology of salivary gland neoplasia, radiation therapy, and chemotherapy and targeted therapy for salivary gland malignancies. The book closes with a discussion of pediatric salivary gland pathology, traumatic injuries of the salivary glands and miscellaneous pathologic processes of the salivary glands and ducts, including a section on saliva as a diagnostic fluid. The book is intended for a very diverse audience, including academic oral and maxillofacial surgeons, otolaryngologists / head and neck surgeons, general surgeons, as well as residents in these disciplines. Private practitioners will want to place this publication on the bookshelves of their offices so as to consult the textbook when evaluating a patient with salivary gland pathology.

Chapter 1
Surgical Anatomy, Embryology, and Physiology of the Salivary Glands

John D. Langdon, FKC, MB BS, BDS, MDS, FDSRCS, FRCS, FMedSci

Outline

1. Introduction
2. The Parotid Gland
   1. Embryology
   2. Anatomy
   3. Contents of the Parotid Gland
   1. The Facial Nerve
   2. Auriculotemporal Nerve
   3. Retromandibular Vein
   4. External Carotid Artery
   5. Parotid Lymph Nodes
   6. Parotid Duct
   7. Nerve Supply to the Parotid
3. The Submandibular Gland
   1. Embryology
   2. Anatomy
4. The Superficial Lobe
5. The Deep Lobe
6. The Submandibular Duct
7. Blood Supply and Lymphatic Drainage
8. Nerve Supply to the Submandibular Gland
   1. Parasympathetic Innervation
   2. Sympathetic Innervation
   3. Sensory Innervation
9. The Sublingual Gland
   1. Embryology
   2. Anatomy
   1. Sublingual Ducts
   2. Blood Supply, Innervation, and Lymphatic Drainage
10. Minor Salivary Glands
11. Histology of the Salivary Glands
12. Control of Salivation
13. Summary
14. References

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 0.5 liters of saliva are produced each day but the rate varies throughout the day. At rest, about 0.3 ml/min are 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.

The Parotid Gland

Embryology

The parotid gland develops as a thickening of the epithelium in the cheek of the oral cavity in the 15 mm Crown Rump length embryo. This thickening extends backwards towards 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 intra-uterine life. These projections then merge to form the deep lobe of the parotid gland. By the sixth month of intra-uterine life the gland is completely canalized. Although not embryologically a bilobed structure, the parotid comes to form a larger (80%) superficial lobe and a smaller (20%) deep lobe joined by an isthmus between the two major divisions of the facial nerve. The branches of the nerve lie between these lobes invested in loose connective tissue. This observation is vital in the understanding of the anatomy of the facial nerve and surgery in this region (Berkovitz, et al. 2003).

Anatomy

The parotid is the largest of the major salivary glands. It is a compound, tubuloacinar, merocrine, exocrine gland. In the adult, the gland is composed entirely of serous acini.

The gland is situated in the space between the posterior border of the mandibular ramus and the mastoid process of the temporal bone. The external acoustic meatus and the glenoid fossa lie above together with the zygomatic process of the temporal bone (Figure 1.1). On its deep (medial) aspect lies the styloid process of the temporal bone. Inferiorly, the parotid frequently overlaps the angle of the mandible and its deep surface overlies the transverse process of the atlas vertebra.

Figure 1.1 A lateral view of the skull showing some of the bony features related to the bed of the parotid gland. 1: Mandibular fossa; 2: Articular eminence; 3: Tympanic plate; 4: Mandibular condyle; 5: Styloid process; 6: Ramus of mandible; 7: Angle of mandible; 8: Mastoid process; 9: External acoustic meatus. Source: Surgical Management of the Infratemporal Fossa. (J. Langdon, B. Berkovitz & B. Moxham). ISBN 9781899066797. Reproduced with permission of Taylor & Francis Books UK.

The shape of the parotid gland is variable. Often it is triangular with the apex directed inferiorly. However, on occasion it is more or less of even width and occasionally it is triangular with the apex superiorly. On average, the gland is 6 cm in length with a maximum of 3.3 cm in width. In 20% of subjects a smaller accessory lobe arises from the upper border of the parotid duct approximately 6 mm in front of the main gland. This accessory lobe overlies the zygomatic arch.

The gland is surrounded by a fibrous capsule previously thought to be formed from the investing layer of deep cervical fascia. This fascia passes up from the neck and was thought to split to enclose the gland. The deep layer is attached to the mandible and the temporal bone at the tympanic plate and styloid and mastoid processes (McMinn, et al. 1984; Berkovitz and Moxham 1988; Williams 1995; Ellis 1997). Recent investigations suggest that the superficial layer of the parotid capsule is not formed in this way, but is part of the superficial musculo-aponeurotic system (SMAS) (Mitz and Peyronie 1976; Jost and Levet 1983; Wassef 1987; Thaller, et al. 1989; Zigiotti, et al. 1991; Gosain, et al. 1993; Flatau and Mills 1995). Anteriorly, the superficial layer of the parotid capsule is thick and fibrous but more posteriorly, it becomes a thin translucent membrane. Within this fascia are scant muscle fibers running parallel with those of the platysma. This superficial layer of the parotid capsule appears to be continuous with the fascia overlying the platysma muscle. Anteriorly, it forms a separate layer overlying the masseteric fascia, which is itself an extension of the deep cervical fascia. The peripheral branches of the facial nerve and the parotid duct lie within a loose cellular layer between these two sheets of fascia. This observation is important in parotid surgery. When operating on the parotid gland, the skin flap can either be raised in the subcutaneous fat layer or deep to the SMAS layer. The SMAS layer itself can be mobilized as a separate flap and can be used to mask the cosmetic defect following parotidectomy by reattaching it firmly to the anterior border of the sternocleidomastoid muscle as an advancement flap (Meningaud, et a...