Parotid Gland: Function, Innervation, Diseases Associated

The parotid glands are the main salivary glands in your body. One is located directly above each ear, and the other is located below each ear.

In order to lubricate your mouth and help in eating and digestion, the parotid glands, along with the two other principal salivary glands in your mouth (the submandibular and sublingual), produce saliva (spit).

Some people can develop parotitis, an inflammation of the parotid glands. Treatment options for this could include massages of the parotid gland, heated compresses, or antibiotics.

Some people can develop tumours in the parotid gland. Treatment options include surgery to completely or partially remove the parotid gland, radiation therapy, and chemotherapy.

Function Of Parotid Gland

The parotid glands in your mouth create a particular kind of thin, watery saliva. They also produce amylase, a protein that aids in speeding up the digestion of starch.

Oral and general health are significantly influenced by saliva. As an illustration, the saliva that comes from your parotid glands

• Maintains mouth lubrication.
• Assists with digestion.
• Decreases harmful oral bacteria.
• Helps in cavity prevention for your teeth.

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Where Are the Parotid Glands Located?

The parotid glands are located just in front of and beneath each ear. Sublingual and submandibular major pairs of salivary glands are two more pairs that you have.

The Stensen's duct, which your parotid gland joins, is a tube that brings saliva to your mouth and releases it close to your upper molar teeth. Saliva is transported from your sublingual and submandibular glands to the floor of your mouth (under your tongue) by a tube known as Wharton's duct.

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Blood Supply Of Parotid Gland

Blood is supplied to the parotid by the external carotid artery. The maxillary artery and the superficial temporal artery are two terminal branches. The transverse facial artery, which emerges from the superficial temporal artery and travels anteriorly between the zygoma and parotid duct, supplies the parotid duct, parotid gland, and masseter muscle. 

Following its egress from the medial section of the parotid, the maxillary artery feeds blood to the infratemporal and pterygopalatine fossas. The superficial temporal and maxillary veins come together to produce the retromandibular vein, which supplies the parotid with venous outflow. Prior to reaching the external jugular vein, it may have a different structure as it travels deep to the facial nerve.

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Lymphatic Drainage Of Parotid Gland

The lymph nodes and parotid glands are closely related. The deep and superficial cervical lymphatic systems are served by two nodal levels on just one salivary gland alone. The superficial lobe between the gland and the parotid capsule is where the majority of nodes are found.

 It is important to note that skin tumours on the face or scalp might increase the parotid gland's lymph nodes, a sign that cancer has progressed locally. The superficial preauricular lymph nodes drain the anterior pinna, temporal scalp, eyelids, and lacrimal glands, whereas the parotid substance lymph nodes drain the gland, middle ear, nasopharynx, palate, and external meatus.

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Nerve Supply Of Parotid Gland

The parotid gland is innervated by sympathetic and parasympathetic fibres. Vasoconstriction is a result of sympathetic innervation, and salivation is a result of parasympathetic innervation, both of which come from the glossopharyngeal nerve (CN IX). The inferior salivatory nucleus of the medulla is where the parasympathetic fibres begin, and they pass through the jugular foramen to the inferior ganglia.

 The tympanic plexus, located in the middle ear, is made up of a tiny branch of the glossopharyngeal nerve known as the tympanic or Jacobsen's nerve. The lesser petrosal nerve is formed from these preganglionic fibres, which travel via the middle cranial fossa and out the foramen ovale. 

As a result of their synapses in the otic ganglion, the postganglionic parasympathetic fibres connect to the auriculotemporal nerve to innervate the parotid gland and cause it to release saliva.The neurotransmitters acetylcholine (ACh) and norepinephrine (NE) function in the parotid. 

ACh stimulates acinar activity and ductal transit via attaching to muscarinic receptors. Additionally, it makes use of second messenger activity, resulting in the production of inositol triphosphate, which raises the concentration of calcium in the cells.

 Therefore, salivary secretion rises. Norepinephrine delivers sympathetic nerve impulses to the salivary glands via postganglionic sympathetic fibres; sympathetic output thickens saliva. When NE binds to beta-adrenergic receptors, the adenylate cyclase second messenger system is activated, generating cAMP, phosphorylating proteins, and activating enzymes.

The facial nerve passes via the parotid gland, supplying motor power to the muscles used for facial expression but not innervating the gland.

The sternocleidomastoid and masseter muscles have a close link to the parotid gland. The sternocleidomastoid muscle, which forms the rear boundary of the retromandibular fossa, is innervated by the accessory nerve. 

The mandibular ramus and the back of the masseter muscle are both partially covered by the superficial lobe of the parotid gland. The masseteric nerve, a branch of the mandibular nerve, provides innervation to the masseter muscle.

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What Diseases Are Associated With Parotid Gland?

There are a number of medical diseases that can result in pain and parotid gland swelling, including:

• Sialolithiasis. This is the medical word for calcified stones (calculi), which can form and obstruct your parotid gland ducts. Sialolithiasis causes excruciating swelling that gets worse when you eat.
• Sialadenitis. This phrase refers to an infection of the parotid gland brought on by obstructions, bacteria, or viruses. Staph infections and the mumps virus are the culprits.
• Tumours of the parotid gland. These might manifest in either lobe and enlarge your jaw and face. The majority of parotid gland tumours are not malignant. However, malignant parotid gland tumours can grow.
• Cancer of the parotid gland. Salivary gland malignancies, like adenoid cystic carcinoma and mucoepidermoid carcinoma, are uncommon. In actuality, they account for 6% to 8% of all head and neck malignancies. But if you do get parotid gland cancer, you need to get treated right once to stop the disease from spreading to your lymph nodes.

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Diagnosis Of Parotid Gland Disorders

An accurate diagnosis begins with a physical examination, just like with the majority of medical disorders. Your healthcare professional will check for any pain or swelling near your parotid glands.

They could ask for extra testing if they think there's something wrong with your parotid glands, like:

• Needle Biopsy-  Your doctor will draw fluid from your parotid gland during this treatment using a fine needle. They'll deliver the liquid to a lab for analysis.
• Imaging exams- An MRI, ultrasonography, or computed tomography (CT) scan of the salivary glands may be ordered by your healthcare physician.

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Treatment Of Parotid Gland Disorder

Your condition with your parotid glands will be treated according to its underlying cause. You should expect your doctor to recommend medications if, for instance, a bacterial infection results in swelling of your parotid gland.

If you have parotid gland obstruction, your doctor may advise giving yourself a face massage or sucking on lemon candies to increase salivation. Attempting various drugs to stimulate salivary flow may be tried if this doesn't work. Your doctor might advise having the stones removed via surgery if nonsurgical measures are unsuccessful.

In most cases, parotidectomy, or surgery to remove all or part of your parotid gland, is necessary for parotid gland tumours.

Surgery to remove the gland and/or a chemotherapy and radiation treatment regimen may be required for those with parotid gland cancer.

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