Parotid gland
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This article needs additional citations for verification. (March 2009) |
| Parotid gland | |
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| Salivary glands: #1 is Parotid gland #2 is Submandibular gland #3 is Sublingual gland |
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| Latin | glandula parotidea |
| Gray's | subject #177 693 |
| Artery | transverse facial artery |
| Lymph | preauricular deep parotid lymph nodes |
| MeSH | Parotid+Gland |
The parotid gland is a salivary gland in humans. It is a bilateral structure, and the largest of the salivary glands. It is wrapped around the mandibular ramus, and secretes saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.
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Anatomy [edit]
The word 'parotid' (paraotic) literally means around the ear.
The parotid glands are a pair of serous salivary glands located below and in front of the external acoustic meatus draining their secretions into the vestibule of oral cavity through stensen's duct. They are the largest major salivary glands of the human body.
Position [edit]
Each gland lies posterior to the mandibular ramus and in front of the mastoid process of temporal bone.
Shape [edit]
The gland is roughly wedge shaped when seen superficially and is also wedge shaped when seen on horizontal sections.
Parotid Capsules [edit]
The gland has a capsule of its own of dense connective tissue but is also provided with a false capsule by investing layer of deep cervical fascia. The fascia at the imaginary line between the angle of mandible and mastoid process splits into Superficial lamina and a deep lamina to enclose the gland. Risorius is a small muscle embedded with this capsules substance...
Surfaces [edit]
The gland has four surfaces superficial or lateral,superior, anteromedial and posteromedial.
Borders [edit]
The gland has three borders anterior, medial and posterior.
Ends [edit]
The Parotid gland has two ends- upper end in the form of small superior surface and a lower end(apex).
Relation to other structures [edit]
(1)Superficial or lateral relations: The gland is related superficially to the skin. Superficial fascia, superficial lamina of investing layer of deep cervical fascia and Great auricular nerve (anterior ramus of C2 and C3)
(2) Anteromedial relations: The gland is related anteromedially to the mandibular ramus, masseter and medial pterygoid muscles. A part of the muscle may extend between the ramus and medial pterygoid as the pterygoid process. Branches of facial nerve and parotid duct emerge through this surface.
(3) Posteromedial relations: The gland is related posteromedially to mastoid process of temporal bone with its attached Sternocleidomastoid and digastric muscles, styloid process of temporal bone with its three attached muscles (Stylohyoid, Stylopharyngeus and Styloglossus) and carotid sheath with its contained neurovasculature (Internal Carotid artery, Internal Jugular vein, 9th, 10th, 11th and 12th cranial nerves)
(4) Medial relations: The parotid gland comes into contact with the superior pharyngyeal constrictor muscle at the medial border where the anteromedial and posteromedial surfaces meet. Hence there is a need to examine the fauces in parotitis.
Structures that pass through the gland [edit]
These are from lateral to medial: (1) Facial nerve (2) Retromandibular vein (3) External Carotid artery (4) Superficial temporal artery (5) branches of the great auricular nerve
Blood Supply [edit]
The gland is mainly irrigated by External Carotid artery via the posterior auricular artery and the transverse facial.
Venous Drainage [edit]
Venous return is to the Retromandibular vein.
Lymphatic drainage [edit]
The gland is mainly drained into the preauricular or parotid lymph nodes which ultimately drain to the deep cervical chain.
Nerve Supply [edit]
Innervation is entirely autonomic. Postganglionic sympathetic fibers from superior cervical sympathetic ganglion reach the gland as periarterial nerve plexuses around the external carotid artery and their function is mainly vasoconstriction. The cell bodies of the preganglionic sympathetics usually lie in the lateral horns of upper thoracic spinal segments. Preganglionic parasympathetic fibers leave the brain stem from inferior salivatory nucleus in the glossopharyngyeal nerve and then through its tympanic and then the lesser petrosal branch pass into the otic ganglion. There, they synapse with postganglionic fibers which reach the gland by hitch-hiking via the auriculotemporal nerve, a branch of the mandibular nerve.
Pathology [edit]
Inflammation of one or both parotid glands is known as parotitis. The most common cause of parotitis is mumps. Widespread vaccination against mumps has markedly reduced the incidence of mumps parotitis. Other infections such as bacterial infections can cause parotitis as may blockage of the duct, whether from salivary duct calculi or external compression. Stones mainly occur within the main confluence of the ducts and within the main parotid duct. The patient usually complains of intense pain when salivating and tends to avoid foods which produce this symptom. In addition, the parotid gland may become enlarged upon trying to eat. The pain can be reproduced in clinic by squirting lemon juice into the patient's mouth. Surgery depends upon the site of the stone: if within the anterior aspect of the duct a simple incision into the buccal mucosa with sphinterotomy may allow removal; however, if situated more posteriorly within the main duct, complete gland excision may be necessary.
Swelling of the parotid gland may also indicate the eating disorder bulimia nervosa, creating the look of a heavy jaw line.
Eighty to eighty-five percent of tumors of the parotid gland are benign.[1] The most common of these include pleomorphic adenoma (70% of tumors,[1] affecting predominantly females (60%[1])) and Warthin's tumor. Their importance is in relation to their anatomical position and tendency to grow over time. The tumorous growth can also change the consistency of the gland and cause facial pain on the involved side since the facial nerve travels through the gland.[2]
Fifteen to twenty percent of parotid tumors are malignant with the most common tumors being mucoepidermoid carcinoma and adenoid cystic carcinoma. Critically, the relationship of the tumor to the branches of the facial nerve (CN VII) must be defined because resection may damage the nerves, resulting in paralysis of the muscles of facial expression.
Surgical treatment of parotid gland tumors is sometimes difficult because of the anatomical relations of the facial nerve parotid lodge, as well as the increased potential for postoperative relapse. Thus, detection of early stages of a parotid tumor is extremely important in terms of postoperative prognosis.[1]
Operative technique is laborious, because of relapses and incomplete previous treatment made in other border specialties.[1]
Secretion [edit]
The parotid gland secretes alpha-amylase which is the first step in the decomposition of starches during mastication. It breaks down amylose (straight chain starch) and amylopectin (branched starch) by hydrolyzing alpha 1,4 bonds.
The parotid duct opens into the oral cavity near the upper 2nd molar tooth.
Additional images [edit]
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Lateral head anatomy detail
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Parotid gland
See also [edit]
References [edit]
- ^ a b c d e Alexandru Bucur, Octavian Dincă, Tiberiu Niță, Cosmin Totan, Cristian Vlădan (Mar 2011). "Parotid tumors: our experience". Rev. chir. oro-maxilo-fac. implantol. 2 (1): 7–9. ISSN 2069-3850.(webpage has a translation button)
- ^ Fehrenbach; Herring "Illustrated Head and Neck Anatomy", Elsevier, 2007, p. 172
Last, R.J Regional Anatomy Snell, Richard S. Human Anatomy by Regions
External links [edit]
- Illustration at yoursurgery.com
- lesson4 at The Anatomy Lesson by Wesley Norman (Georgetown University)
- Histology at usc.edu
- Parotid+gland at eMedicine Dictionary
Additional images [edit]
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Mandibular division of the trifacial nerve.
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Sympathetic connections of the otic and superior cervical ganglia.
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Horizontal section through left ear; upper half of section.
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Outline of side of face, showing chief surface markings.
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microscopic ducts surrounded by connective tissue
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