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Parotid Gland

  1. Located on side of face, anterior to mastoid tip and external auditory canal, inferior to zygomatic arch, and superior to the lower border of the angle of the mandible. Anteriorly, it overlaps the masseter muscle.
  2. Stenson's duct enters oral cavity through buccal mucosa opposite upper 2nd molar.
  3. Parasympathetic secretory afferents to the parotid leave the inferior salivary nucleus with the glossopharyngeal nerve and travel via Jacobson's plexus in the middle ear to synapse in the otic ganglion. Post-synaptic fibers are distributed to the parotid by the auriculotemporal nerve.
  4. Facial nerve passes through this gland.
  1. Submandibular Gland
    1. Beneath floor of the mouth, inferior to mylohyoid muscles and superior to digastric muscle.
    2. Marginal mandibular branch of the facial nerve travels in the fascia on the lateral surface of this gland.
    3. Parasympathetic secretory afferents to the submandibular gland arise from the superior salivatory nucleus, and leave the brainstem in the facial nerve. They exit the facial nerve at the geniculate ganglion and travel via the chorda tympani to the lingual nerve. Fibers synapse in the submandibular ganglion, and post-synaptic fibers then enter the gland.
    4. The lingual and hypoglossal nerves lie deep to this gland.
    5. Wharton's duct enters the floor of the mouth near the lingual frenula. 
  2. Sublingual Glands - located below the mucous membrane of the floor of the mouth, adjacent to mandible and mylohyoid muscle. Ten to twelve small caliber ducts drain the gland, some emptying into the submandibular duct, and others draining directly into the floor of the mouth. 
  3. Minor Salivary Glands - small collections of salivary gland tissues are scattered throughout the oral mucosa, and can also be seen in the pharynx, supraglottis, nose and sinuses.  
  4. Parotid Gland:
    1. Parotid gland appears on the 4th week of gestational life from the epithelium of the oro-pharynx.
    2. Agenesis of the parotid glands is rare; may be associated with other facial abnormalities.
    3. Cyst arising from the first branchial cleft may be located within the parotid gland
    4. Largest of the salivary glands and it overlaps the masseter muscle.
    5. VIIth Nr.  passes through and divides the gland into a superficial and deep lobe
    6. The deep surface of the gland lies alongside the back of the throat, near the tonsils Stenson's duct enters oral cavity through buccal mucosa opposite upper 2nd molar.
    7. Parasympathetic secretory afferents to the parotid leave the inferior salivary nucleus with the glossopharyngeal nerve and travel via Jacobson's plexus in the middle ear to synapse in the otic ganglion. Post-synaptic fibers are distributed to the parotid by the auriculotemporal nerve. 
  5. Submandibular Gland
    1. Beneath floor of the mouth, inferior to mylohyoid muscles and superior to digastric muscle.
    2. Marginal mandibular branch of the facial nerve travels in the fascia on the lateral surface of this gland.
    3. Parasympathetic secretory afferents to the submandibular gland arise from the superior salivatory nucleus, and leave the brainstem in the facial nerve. They exit the facial nerve at the geniculate ganglion and travel via the chorda tympani to the lingual nerve. Fibers synapse in the submandibular ganglion, and post-synaptic fibers then enter the gland.
    4. The lingual and hypoglossal nerves lie deep to this gland.
    5. Wharton's duct enters the floor of the mouth near the lingual frenula.  
  6. Sublingual Glands - located below the mucous membrane of the floor of the mouth, adjacent to mandible and mylohyoid muscle. Ten to twelve small caliber ducts drain the gland, some emptying into the submandibular duct and others draining directly into the floor of the mouth.  
  7. Minor Salivary Glands - small collections of salivary gland tissues are scattered throughout the oral mucosa, and can also be seen in the pharynx, supraglottis, nose and sinuses. Minor glands are muco-serous only Ebner gland (posterior lingual gland) like parotid, is pure serous.  
  8. Trauma:
    1. Laceration:  Parenchymal damage only – usually heals by it self.
    2. Injury to Stenson’s duct – should be repaired over a small catheter.
    3. Injury to facial nerve – should be repaired within 72 hours.
    4. Injury to Stenson’s duct may cause chronic salivary fistula.
    5. Acute obstruction or ligation of parotid duct causes complete atrophy of the gland.
    6. Any foreign body should be removed. 
  9. Sialoadinitis:
    1. In viral infection Mumps is the most common infection. Its treatment is symptomatic.
    2. Low grade bacterial infection of salivary gland is usually self limiting.
    3. Stenson’s duct obstruction by Stone/stricture also causes intermittent painful swelling → Sialogram should be done → obstruction should be relieved by →
    4. Transorally (if the stone is near the duct end).
    5. By external incision (If the stone is deep).
    6. Parotidectomy (If multiple stone / stricture is present). 
  10. Acute Suppurative Parotitis:
    1. Characterized by presence of pus and seen in debilitated/ dehydrated/ or in patients with poor oral hygiene.
    2. Commonest causing organism is Staph. aureus.
    3. Initial treatment is proper hydration/ antibiotics/ improving oral hygiene.
    4. If abscess develops then it is drained by giving a J shaped incision (see 1st diagram).

Description: PAROTID_GLAND_FIG1_t

Parotid gland, Fig. 1

Axial contrast-enhanced CT images of parotid glands. Increased attenuation of left parotid gland due to sialadenitis, with intraglandular abcedation (asterisk). Note associated cellulitis of parapharyngeal space (arrowhead).

Description: PAROTID_GLAND_FIG2_t

Parotid gland, Fig. 2

Axial T2-weighted spin-echo image of parotid glands. Lobulated soft tissue mass with high signal intensity, in the superficial part of the left gland. Pleomorphic adenoma.

 

 

 

Description: PAROTID_GLAND_FIG3A_t

Description: PAROTID_GLAND_FIG3B_t

Description: PAROTID_GLAND_FIG3C_t

 

Parotid gland, Fig. 3: Axial T2-weighted (a) and gadolinium-enhanced T1-weighted spin-echo images (b 1 cm caudal to c) of a patient with a history of left facial nerve paralysis for several months. Ill-defined soft tissue mass in the left parotid gland (asterisk); by perineural tumour spread along the auriculotemporal nerve (arrowhead, b-c), the neoplasm reaches the main stem of the mandibular nerve, causing denervation muscle atrophy of the masticator muscles (compare masseter muscles (arrows) and lateral pterygoid muscles (arrowheads, a).

  1. Salivary Gland Tumors
    1. Tumors of the salivary glands are grouped into epithelial, nonepithelial, and metastatic categories. Benign epithelial tumors include pleomorphic adenoma (80%), Warthin tumor, monomorphic adenoma, intraductal papilloma, oncocytoma etc.
    2. Benign nonepithelial tumors (mesenchymal origin) include lipoma, hemangioma, lymphangioma (cystic hygroma), and neural sheath tumors. Q
    3. Pleomorphic adenomas make up 70% of parotid gland tumors and 50% of submandibular gland tumors.
    4. Of minor SGTs, 50% are malignant.
    5. Mucoepidermoid cancer is the most common parotid malignancy.
    6. Overall, adenoid cystic carcinoma is the most common malignant tumor of all minor salivary glands and, specifically, the submandibular gland 
  2. Benign Epithelial Tumors
    1. Pleomorphic adenoma
    2. Commonly located at the tail of the parotid.
    3. Lesions arising from the deep lobe develop primarily within the parapharyngeal space and present late with symptoms related to pharyngeal compressionQ
    4. It consists of epithelial and connective tissue. It is round, smooth, and freely mobile.
    5. The term pleomorphic adenoma describes its multiples histological components, including myxoid, mucoid, chondroid, and other element.
    6. Malignant mixed tumour has a tendency for perineural and perivascular invasion and significant cellular atypia
    7. It has a thin, delicate capsule with occasional projections into the surrounding parotid tissue, so obtaining clean margins is mandatory to minimize recurrence.
    8. If the parotid is the gland involved, superficial parotidectomy with standard facial nerve dissection and preservation is the procedure of choice.
  3. Warthin tumor (ie, papillary cystadenoma lymphomatosum, cystic papillary adenoma, adenolymphoma) Q
    1. It is the second most common benign tumour of the parotid gland.
    2. In gross appearance, it is a smooth, soft parotid mass.
    3. It is well encapsulated and contains multiple cysts.
    4. Histologically, it has a heavy lymphoid stroma and aciniform epithelial cells lining the cystic areas with papillary projections.
    5. Malignant transformation has not been observed. The recurrence rate is 5%.
    6. The Warthin tumor tends to be bilateral (10% of cases) 
  4. Lymphoepithelial hyperplasia (Mikulicz disease)
    1. Manifest as a diffuse enlargement of the parotid gland, or it may manifest as a discrete mass.
    2. Histologically, the lesion is composed of a diffused, well-organized lymphoid tissue and lymphocytic interstitial infiltrate.
    3. More frequent in females, with peak incidence in the fourth and fifth decades.
    4. Growth of this tumor is slowly progressive, and it gives rise to pain around the ear or the retromandibular area.
  5. Intraductal papilloma
    1. Intraductal papilloma is a small, smooth lesion that is found in the submucosal layer. Microscopically, it consists of a cystically dilated duct partially lined with a cuboidal epithelium with complex anatomizing papillary fronds filling the cystic area.  
  6. Oxyphil adenoma (oncocytoma)
    1. Oncocytomas of the salivary glands are very uncommon.
    2. Such neoplasms occur in women, after fifth decade (female-to-male ratio of 2:1), and the superficial lobe of the parotid is commonly involved.




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