Surgical Anatomy of Salivary Glands

Surgical Anatomy of Salivary GlandsDr. Mohey Eddin ElbannaProf. of General Surgery Ain Shams University

Salivary Glands

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Prof. Mohey El-Banna

Embryology The major salivary glands develop from the 6th6th-8th weeks of gestation as outpouchings of oral ectoderm into the surrounding mesenchyme. The parotid develops first, growing posteriorly as the facial nerve advances anteriorly; eventually, the fully developed parotid surrounds VII. However, the Parotid is the last to become encapsulated, after the lymphatics develop, resulting in its unique anatomy with entrapment of lymphatics in the parenchyma of the gland3 Prof. Mohey El-Banna

Salivary epithelial cells are often included within these lymph nodes, leading to development of Warthins tumors and Lymphoepithelial cysts within the Parotid gland. The other major salivary glands do NOT have intraparenchymal lymph nodes.4 Prof. Mohey El-Banna

Function of SalivaAt least 8 major functions of saliva have been identified: 1) Moistens oral mucosa. Mucin layer is the most important nonimmune defense mechanism in the oral cavity. 2) Moistens dry food and cools hot food. 3) A medium for dissolved foods to stimulate the taste buds. 4) Buffers oral cavity contents due to high concentration of bicarbonate ions. 5) Digestion. Alpha-amylase, contained in saliva, breaks 1-4 Alpha1glycoside bonds, while lingual lipase helps 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 calcium and phosphate. 8) Protects the teeth. This signifies a saliva protein coat on the teeth which contains antibacterial compounds. Thus, salivary hypofunction results in dental caries.

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The intraoral complications of salivary hypofunction 1) Candidiasis 2) Oral Lichen Planus (usually painful) 3) Burning Mouth Syndrome (normal appearing oral mucosa with a subjective sensation of burning) 4) Recurrent aphthous ulcers 5) Dental caries. The best way to evaluate salivary function is to measure the salivary flow rate in stimulated (e.g., by using a parasympathomimetic as pilocarpine) and unstimulated states. Xerostomia is NOT a reliable indicator of salivary hypofunction. There is a hierarchy of sensory stimuli such that swallow>mastication>taste>smell>sight>thought. Stimulation results in an increase in total salivary flow from 0.3 cc/min to >1 cc/min. The salivary response is directly related to a subjects state of hunger

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The Parotid Gland The largest salivary gland Lies wedge-shaped between the mandible wedgeand sternomastoid and over both Relations: Above: external auditory meats and temporotemporomandibular joint Below: post belly digastric Anteriorly: mandible and masseter Medially: styloid process and its muscles7 Prof. Mohey El-Banna

Structures at the Angle of the Mandible Medial relations of the parotid: the styloid process and its muscles separate the gland from the internal jugular vein Internal carotid artery The last four cranial nerves Lateral wall of the pharynx8 Prof. Mohey El-Banna

Relations of the Parotid

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Parotid Bed

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Deep relations of Parotid

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Fascia The parotid is enclosed in a split in the investing fascia The parotid lymph nodes lie both on and below the parotid gland Antero-inferiorly, the fascia is Anterothickened to form the stylomandibular ligament; the only structure that separates the parotid from the submandibular glands12 Prof. Mohey El-Banna

The Facial Nerve The parotid gland is divided into superficial and deep lobes by three structures traversing the gland: The Facial Nerve The retromandibular vein (post facial) formed by the superficial temporal and maxillary The external carotid artery dividing at the neck of the mandible into the superficial temporal and maxillary

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Relation of the Facial Nerve and Parotid The parotid develops in the crotch formed by the 2 divisions of the facial nerve As it enlarges it overlaps the nerve trunks, the superficial and deep parts fuse and the nerve becomes buried within the gland It is not a sandwich14 Prof. Mohey El-Banna

Facial Nerve

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The Facial Nerve Emerges from the stylomastoid foramen Winds laterally to the styloid process Surgical Exposure In the inverted V between the bony external auditory meatus and the mastoid process Just beyond the point the nerve dives into the post aspect of the parotid and bifurcates almost immediately into its two main divisions

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Branches of the Facial N The nerve then gives rise to 2 divisions: 1) Temperofacial (upper) 2) Cervicofacial (lower) 17

Followed by 5 terminal branches: 1) Temporal 2) Zygomatic 3) Buccal 4) Marginal Mandibular 5) Cervical Prof. Mohey El-Banna

Branches

The two divisions may be completely separate, may form a plexus of intermingling fibers, or may form crosscrosscommunications that be divided safely during dissection

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Nerve Injury Clinical examination of the Parotid should include examination of the Facial nerve Malignant tumors of the parotid may involve VII and cause facial palsy, while benign tumors never affect VII During Superficial Parotidectomy, the nerve is exposed posteriorly in the space bet the bony canal of external auditory meatus and the mastoid process It is then traced anteriorly into the gland to excise the gland superficial to nerve branches19 Prof. Mohey El-Banna

The Parotid Duct Stensens duct is 5 cm long. Arises from the anterior part of the gland and runs over the masseter one finger below the zygomatic arch to pierce the buccinator and open opposite the second upper molar tooth

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Parotid Duct orifice Clinical examination of the parotid gland should include examination of the duct orifice opposite the upper 2nd molar for signs of inflammation, and palpated for stone Parotid Sialogram is performed by injecting a contrast through a canula placed in the orifice of the duct21 Prof. Mohey El-Banna

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Submandibular Gland Large superficial lobe and a small deep lobe, that connect around the mylohyoid Superficial lobe lies at the angle of the Jaw, wedged bet the mandible and mylohyoid and overlapping the digastric

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Superficial and Deep Relations Superficially: The skin, the platysma, the capsule (deep fascia), the cervical branch of Facial Nerve, and the Facial Vein Deeply: the deep aspect lies against the mylohyoid for the most part. But posteriorly lies on the hyoglossus and comes in contact with the lingual and hypoglossal nerves. Both nerves lie on the hyoglossus as they pass forward to the tongue

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The facial Artery Posterior Arches over its superior aspect to reach inferior border of the mandible and then ascends on to the face in front of the masseter

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Facial artery


The Submandibular Duct Arises from the deep part of the gland, runs forward to open at the side of the frenulum linguae Lies beneath the mucosa of the floor of the mouth along the side of the tongue Lingual nerve loops around the duct, doubledoublecrossing it, by passing from lateral beneath, then medial The sublingual salivary gland is also medial to the duct.28 Prof. Mohey El-Banna

Clinical Applications Submandibular LN are adherent to the gland and partly between it and the mandible Differentiating bet submandibular LN and Salivary gland: The salivary gland can be palpated bimanually as it extends into the floor of the mouth. The Lymph Nodes are only felt below the mandible. LN may be multiple and a space separates them from the mandible29 Prof. Mohey El-Banna

Clinical Applications A stone in the submandibular duct can be felt bimanually in the floor of the mouth and can be seen if large The presence of LN adherent to the gland makes removal of the gland part of block neck dissection

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Autonomic Innervations Parasympathetic Stimulation results in abundant, watery saliva with a decrease in [amylase] in saliva and an increase in [amylase] in the serum. Acetylcholine is the active neurotransmitter, binding at muscarinic receptors in the salivary glands. The parasympathetic nervous system is the primary instigator of salivary secretion. Parasympathetic Interruption to salivary glands results in atrophy, while sympathetic interruption doesnt cause a significant change. It was once thought that the sympathetic nervous system antagonizes the parasympathetic nervous system, but this is now known not to be true

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Autonomic Innervation In the case of the parotid, parasympathetic fibers originate from CN IX In the case of the Submandibular and Sublingual glands, the parasympathetic fibers originate in CN VII

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Sympathetic Innervation Stimulation by the sympathetic nervous system results in a scant, viscous saliva rich in solutes with an increase in [amylase] in the saliva and no change in [amylase] in the serum. For all of the salivary glands, these fibers originate in the Superior Cervical ganglion and travel with arteries to reach the glands: 1) External Carotid artery for the Parotid 2) Lingual artery for the Submandibular, and 3) Facial artery in the case of the Sublingual.

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The Most Common Tumors Histologically, salivary gland tumors are the most heterogenous group of tumors of any tissue in the body Of salivary gland neoplasms, >50% are benign Approximately 70% to 80% of all salivary gland neoplasms originate in the parotid The palate is the most common site of minor salivary gland tumors The frequency of malignant lesions varies by site.34 Prof. Mohey El-Banna

Malignant Tumors Approximately 20-25% of parotid, 35-40% of 2035submandibular tumors, 50% of palate tumors, and > 90% of sublingual gland tumors are malignant The most common benign salivary tumor is pleomorphic adenoma, comprising 50% of all salivary tumors and 65% of parotid gland tumors The most common malignant salivary tumor is the mucoepidermoid carcinoma, comprising 10% of all salivary gland neoplasms and 35% of malignant salivary gland neoplasms, occurring most often in the parotid gland.

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Other types of malignant tumors

Monomorphic Adenoma (Warthins tumor) Malignant mixed salivary tumor (Malignant Pleomorphic carcinoma) Adenoid Cystic Carcinoma Acinic cell cancer Adenocarcinoma Squamous cell carcinoma36 Prof. Mohey El-Banna

Q&A1- Mark following statements as true (T) or false (F):

A-The Parotid gland is the last to be encapsulated B-The Parotid gland has intraparenchymal lymphatics C- The hypoglossal nerve divides the parotid gland into superficial and deep lobes D-The parotid duct opens in the floor of the mouth E-The parotid secretion is mucus and viscous

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Q 22- Mark following statements as true (T) or false (F):

A-The Parotid gland is separated from the submandibular gland by the stylomastoid ligament B- Benign tumors of the parotid may cause facial never palsy C- The facial Nerve divides into 2 trunks, each giving 3 branches D- The superficial and deep lobes of the parotid gland are completely separated by the facial nerve E- The facial nerve trunk may be injured during superficial parotidectomy

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Q33-Mark following statements as true (T) or false (F):

A-The submandibular gland consists of a large deep lobe and a small superficial lobe B-Both lobes of the submandibular gland are separated by the facial nerve C-Salivary stones form more commonly in the submandibular duct D-Submandibular sialadenectomy is part of block neck dissection E-Hypoglossal N runs below the deep part of the submandibular gland39 Prof. Mohey El-Banna

Q44-Mark following statements as true (T) or false (F):

A- Pleomorphic adenoma is the most common salivary gland tumor B- Mucoepidermoid carcinoma is the most common salivary gland tumor C- Parotid gland tumors are most commonly malignant D- Sublingual gland tumors are most commonly malignant E- Malignant Salivary gland tumors are treated by Surgical excision followed by postoperative radiotherapy

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Key to Answers Q 1 A: T, B: T, C: F, D: F, E: F Q 2: A: T, B: F, C: F, D: F, E: TQ 3: A:F, B: F, C:T, D: T, E: T Q 4: A: T, B: F, C: F, D: T, E: T

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Surgical Anatomy of Salivary Glands

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