Anatomy

Parotid Gland Anatomy (Figs. 2-1, 2-2)

• located between the ramus of the mandible and the external auditory canal and mastoid tip, overlies the masseter muscle (anteriorly) and sternocleidomastoid muscle (posteriorly)

• facial nerve divides the parotid gland artificially into deep and superficial lobes

• the superficial layer of the deep cervical fascia forms the parotid gland fascia which incompletely surrounds the gland

• Histological Cell Type: basophilic, serous cells

• Stylomandibular Ligament: formed by the fascial envelope between the styloid process and the mandible, separates the parotid gland from the submandibular gland

• Stenson's Duct: passes over masseter, through buccinator muscle, and opens opposite to the second upper molar (follows along plane from external auditory canal to columella and buccal branch of CN VII)

Venous Drainage

• superficial temporal vein + maxillary vein ^ retromandibular vein

• retromandibular vein ^ passes deep to the facial nerve ^ anterior and posterior branches

• anterior retromandibular vein + facial vein ^ common facial vein ^ internal jugular vein

Figure 2-1. Positions of the major salivary glands and related nerves.

Sublingual Gland-

Lingual Nerve -

Auriculotemporal Nerve

Parotid Gland

Submandibular Ganglion

Submandibular Gland

Figure 2-1. Positions of the major salivary glands and related nerves.

Figure 2—2. Position of the facial nerve, as illustrated following a superficial parotidectomy. The residual parotid gland illustrated above is the deep lobe.

Facial Nerve and Branches

Parotid Gland (Dissected)

Figure 2—2. Position of the facial nerve, as illustrated following a superficial parotidectomy. The residual parotid gland illustrated above is the deep lobe.

posterior retromandibular vein + posterior auricular vein (over SCM) ^ external jugular vein

Submandibular Gland Anatomy

• within the submandibular triangle (inferior to mylohyoid muscle, superior to the digastrics)

• superficial layer of the deep cervical fascia envelops the gland and contains the marginal mandibular nerve

• hypoglossal nerve runs deep to the digastric tendon and medial to the deep layer of the deep cervical fascia

• facial artery arises from the external carotid artery and courses medial to the posterior digastric muscle then hooks over the muscle to enter the gland and exits into the facial notch of the inferior mandible

• lingual artery runs along the lateral aspect of the middle constrictors, deep to the digastrics, and anteriorly and medially to the hyoglossus

• Histological Cell Type: mixed cells (serous and mucinous)

• Wharton's Duct: opens lateral to frenulum in the anterior portion of the floor of mouth, behind the incisors

Minor Glands and Sublingual Gland Anatomy

• Sublingual Gland: located within the submucosal layer of the floor of mouth

• Minor Salivary Glands: several hundred glands within the submucosal layer of the oral cavity, oropharynx, nasopharynx, and hypopharynx

• Histological Cell Type: mucinous

• Ducts of Rivinus: drain at the sublingual fold or plica of the floor of mouth

Embryology

• derived from the first pharyngeal pouch

• 4th week: parotids formed from the posterior stomodeum (ectodermal) forming cords through the mesenchyme which later forms the capsule; parotid encapsulates late allowing entrapment of lymphoid tissue within the parotid fascia

• 6th week: submandibular glands form as buds in the floor of mouth then grow into the submandibular triangle (endodermal)

• 9th week: sublingual glands form as multiple buds in the floor of mouth (endodermal)

• Pathology: aberrant salivary gland tissue, accessory glands (most common in the parotid), diverticuli

Histology (Fig. 2-3)

• Secretory Unit: acini cells (contain abundant endoplasmic reticulum, golgi apparatus, and secretory granules; produces saliva) — intercalated duct — striated duct (contain abundant mitochondria for energy for water and electrolyte transport) — excretory duct

• myoepithelial cells surround acini and intercalated ducts

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