ANATOMY Major salivary glands Minor salivary glandsPairedparotid , Palate ,Submandibular , nasal cavity ,Sublingual . oral cavity .
EmbryologyThe major salivary glands develop from the 6th-8th weeks ofgestation as outpouchings of oral ectoderm into the surroundingmesenchyme. The parotid enlage develops first, the fullydeveloped parotid surrounds CN VII. Parotid gland develops in itsunique anatomy with entrapment of lymphatics in the parenchymaof the gland. Furthermore, salivary epithelial cells are oftenincluded within these lymph nodes.The minor salivary glands arise from oral ectoderm andnasopharyngeal endoderm. They develop after the major salivaryglands.During development of the glands, autonomic nervous systeminvolvement is crucial; sympathetic nerve stimulation leads toacinar differentiation while parasympathetic stimulation is neededfor overall glandular growth.
Parotid glandThe parotid gland overlies the angle of themandible .Superiorly is related to zygoma .Posteriorlly is related to cartilage of ear canal .Medially is related to parapharyngal space
Facial nerve & parotid glandThe facial n. exits the stylomastoid foramen andruns through the substance of the parotidgland , splitting into its 5 main branches. The plain of facial nerve is used to divide thegland into “ superfacial “ and “ deep “ lobes .
Branches of facial n. within parotid gland2 divisions: 1) Temperofacial (upper) 2) Cervicofacial (lower)5 terminal branches: 1) Temporal 2) Zygomatic 3) Buccal 4) Marginal Mandibular 5) Cervical3
The surgical landmarks of CN VIIintraoperatively :1) Tragal pointer – points to the main trunk of CN VII proximal tothe Pes and 1-1.5 cm deep and inferior to the pointer .2) Tympanomastoid suture – traced medially, the main trunk ofVII is encountered 6-8 mm deep to the suture line .3) Posterior belly of Digastric muscle – is a guide to theStylomastoid foramen; the trunk of VII is just superior andposterior to the cephalic margin of the muscle .4) Styloid process – sits 5-8 mm deep to the Tympanomastoidsuture; the trunk of VII lies on the posterolateral aspect of theStyloid near its base .
The Auriculotemporal nerve :The Auriculotemporal nerve , a branch of V-3, runs anterior to theEAM, paralleling the superficial temporal artery and vein. This nervecarries Parasympathetic postganglionic fibers from the otic ganglionto the Parotid gland. Thus, when this nerve is injuredintraoperatively, aberrant parasympathetic innervation to the skinresults in Frey’s Syndrome (i.e., gustatory sweating). This nervemay be resected intentionally to avoid Frey’s Syndrome. In addition,the Auriculotemporal nerve provides sensory innervation to theparotid capsule, and the skin of the auricle and temporal region. Asa result, referred pain from parotitis can involve the auricle, EAM,TMJ, and temples.
Parotid ductStensen’s duct (parotid duct) arises from the anteriorborder of the Parotid and runs superficial to themasseter muscle, then turns medially 90 degrees topierce the Buccinator muscle at the level of thesecond maxillary molar where it opens onto the oralcavity. The buccal branch of CN VII runs with theparotid duct. The duct measures 4-6 cm in lengthand 5 mm in diameter.
Submandibular glandSuperolaterally , the submandibular gland abutsthe body of the mandibleMedially the lingual and hypoglossal nerves,Anteriorly , the mylohyoid muscle .Posteriorly , the tail of parotid gland .Lateraly , marginal branch of facial n.
The Submandibular duct (Wharton’s duct) :Wharton’s duct exits the medial surface of the gland and runsbetween the Mylohyoid (lateral) and Hyoglossus muscles and on tothe Genioglossus muscle. Wharton’s duct empties into the intraoral cavity lateral to thelingual frenulum on the anterior floor of mouth. The length of theduct averages 5 cm.The Lingual nerve wraps around Wharton’s duct, starting lateraland ending medial to the duct, while CN XII parallels theSubmandibular duct, running just inferior to it.The identification of CN XII, the Lingual nerve, and Wharton’s ductis absolutely essential prior to resection of the gland.
Sublingual GlandThis gland lies just deep to the floor of mouth mucosa betweenthe mandible and Genioglossus muscle. It is boundedinferiorly by the Mylohyoid muscle. Wharton’s duct and the Lingual nerve pass between theSublingual gland and Genioglossus muscle.The Sublingual gland has no true fascial capsule.The Sublingual gland is drained by approximately 10 small ducts(the Ducts of Rivinus), which exit the superior aspect of thegland and open along the Sublingual fold on the floor ofmouth.Occasionally, several of the more anterior ducts may join to forma common duct (Bartholin’s duct), which typically emptiesinto Wharton’s duct.
Minor Salivary GlandsThe minor salivary glands lack a branching network of drainingducts. Instead, each salivary unit has its own simple duct.The minor salivary glands are concentrated in the Buccal, Labial,Palatal, and Lingual regions. In addition, minor salivary glands maybe found at the superior pole of the tonsils (Weber’s glands), thetonsillar pillars, the base of tongue (von Ebner’s glands),paranasal sinuses, larynx, trachea, and bronchi.The most common tumor sites derived from the minor salivaryglands are the palate, upper lip, and cheek.
Microanatomy of the Salivary GlandsThe secretory unit (salivary unit) consists of the acinus, myoepithelialcells, the intercalated duct, the striated duct, and the excretory duct. All salivary acinar cells contain secretory granules; in serous glands,these granules contain amylase, and in mucous glands, these granulescontain mucinMyoepithelial cells send numerous processes around the acini andproximal ductal system (intercalated duct), moving secretions towardthe excretory duct.The lumen of the acinus is continuous with the ductal system, madeup of (from proximal to distal) the intercalated duct, the striated duct,and the excretory duct.The intercalated duct is lined by low cuboidal epithelial cells.The striated duct is lined by simple cuboidal epithelial cells proximallyExcretory ducts are lined by simple cuboidal epithelium proximally andstratified cuboidal or pseudostratified columnar epithelium distally.
The sublingual glands are another tubuloacinar gland, but in this case mucous cellspredominate. Acini are composed of both serous and mucous cells with the serouscells mostly displaced to the terminal portion of the acini as outpocketings. Theyappear as darkly staining crescents of cells (serous demilunes) around the ends ofmucous tubules
Function of Saliva1) Moistens oral mucosa.2) Moistens dry food and cools hot food.3) Provides a medium for dissolved foods to stimulate the taste buds.4) Buffers oral cavity contents. Saliva has a high concentration of bicarbonate ions.5) Digestion. Alpha-amylase, contained in saliva, breaks 1-4 glycoside bonds, while lingual lipasehelps break down fats.6) Controls bacterial flora of the oral cavity.7) Mineralization of new teeth and repair of precarious enamel lesions. Saliva is high in calciumand phosphate.8) Protects the teeth by forming a “Protective Pellicle”. This signifies a saliva protein coat on theteeth which contains antibacterial compounds. Thus, problems with the salivary glandsgenerally result in rampant dental caries.
Pseudoparotomegaly1- Hypertrophy of the masseter ( young women ).2- Aging ( absorption of adipose tissue & salivary glands become more obvious ) .3- Dental causes ( dental infection spreads to lymph nodes within parotid or submandibular ) .
4- Tumors in parapharyngeal space- Chemodectoma .- Glomus vagal tumors .- Schwanoma of vagus .- Schwanoma of sympathetic trunk .- Enlarged lymph nodes .-T.B.- Metastatic.Tumour → displace parotid or submandibular gland .
5- Tumors of Infratemporal fossa- Haemangioma .- Haemangiosarcoma .- Leimyosarcoma .- Hydatid cyst .- Liposarcoma .- Metastatic lymph node(s) .- Tumour extend through mandibular notch or under zygomatic arch .
Mucoceles of salivary glandsMucoceles- Most common reactive condition of the minor salivary glands- Mucoceles form when trauma to excretory ducts of the minor glands allows the spillage of mucus into the surrounding connective tissue- formation of painless, smooth surfaced, bluish lesions
mucocelesThe lower lip is the mostfrequent site followed by thebuccal mucosa , the ventralsurface of the tongue, the floorof the mouth, and theretromolar region .Treatment:• observation• surgical excision .
RanulasRanulas- The result of blocked sublingual gland ducts .- Ranulas are unilateral, soft-tissue lesions, often with a bluish appearance.- They vary in size and may cross the midline of the mouth and cause deviation of the tongue- A mucosal extravasation that herniates the mylohyoid muscle is called a "plunging" ranula
Treatment of ranulaTreatment of a RanulaSurgical excision of the involved glandand marsupializationMarsupialization: suturing its walls toan adjacent structure, leaving thepacked cavity to close by granulation
Irradiation Reaction- A common side effect of tumoricidal doses of ionizing radiation is xerostomia- Frequent sips of water and frequent mouth care are the most effective interventions for xerostomia- Saliva substitutes (e.g., mixed solutions of methylcellulose, glycerin, and saline) or pilocarpine hydrochloride may help these symptoms
SialectasisPathogenesis : - The epithelial debris within salivary gland lead to formation of a stone which blockades the salivary gland duct , causing swell up of the gland & if persists for some days , infection & abscess formation will occur .
Sialectasis - Clinical picture- History : - painful swelling of the gland during meal .- Examination : - 1- Submandibular gland ; stone in the duct can be palpated or seen . 2- parotid gland : the mout of the duct is oedamatous & pouting . Drainage of saliva from the duct can be seen when massage the gland .
Sialectasis - Investigations1- Plain radiograph : radio opaque stone .2- Sialogram : normal . Overfilled Obstruced duct Sialectasis ; cystic , globular or saccular
salivary stones80 % occur in the submandibular gland10 % occur in the parotid gland7 % occur in the sublingual gland80 % of submandibular stones are radio opaque Most parotid stones are radiolucent
If partial obstruction occurs swelling may be mild with chronic painful enlargement of the gland
If diagnostic doubt then stone can be demonstrated by sialogram
Sialectasis- treatment1- No treatment .2- Peroral removal of a calculus .3- Marsupialization of the duct .4- Ligation of duct ( dismissed ) .5- Duct dilatation ( dismissed ) .6- Tympanic neurectomy .7- Removal of submandibular gland .8- Total parotidectomy .
Treatment is by either removal of stone from duct or excision of the gland
Necrotizing Sialometaplasia- Usually involves minor salivary glands -- Occurs secondary to vascular infarct due to -• smoking, trauma, DM, vascular disease,- Age range 23-66 yrs- 1-4 cm ulceration- resembles mucoepidermoid carcinoma and SCCA clinically and histologically- Usually heal in 6-10 weeks-
Nutrition DisordersNutrition disorders such as pellagra (ie,niacin deficiency), kwashiorkor (ie, proteindeficiency), beriberi (i.e, thiaminedeficiency), and vitamin A deficiency areassociated with parotid gland enlargementMalabsorption syndromes (e.g., parasiticand protozoan infections, amebicdysentery, celiac sprue) also can causemalnutrition and result in salivary gland dysfunctionObesity & parotid ( excessive ingestion of starch ) .
Metabolic Conditions Patients with alcoholic cirrhosis oftenexperience asymptomatic enlargements of their parotid glands, which are attributed to chronic protein deficiency Diabetes mellitus and hyperlipidemia cause fatty infiltrations that replace the functional parenchyma of the salivary glands and decrease the flow of saliva
Immunologic conditionsHIV may manifest with parotid glandenlargement and parotidlymphadenopathy often are observed inthese immunocompromised patients.Parotid gland enlargement may be causedby benign lymphoepithelial lesions in thegland, hypertrophied periparotid lymphnodes, or secondary infections from CMV