The Anatomy of the Parotid Gland

The parotid glands are the largest of the three pairs of major salivary glands. When you eat, it isn't just your teeth and jaw that help process your food. Saliva helps to breaks down the food you eat, move it down the throat, and protect you from infections. The other major salivary glands are the submandibular glands and the sublingual glands. In addition, there are hundreds of minor salivary glands.

Anatomy

The parotid glands develop early—at just six to seven weeks into gestation. Starting as tiny buds in the oral cavity, these glands eventually form two lobes that sit just in front of the ears on either side, stretching from the cheekbone down to the jawline. Blood is supplied to the parotid gland by the external carotid artery.

Roughly the size of a walnut, the two lobes of the parotid gland are separated by the facial nerve, or cranial nerve VII. The location of this nerve in relation to the parotid gland is particularly important during surgical procedures involving the parotid gland, since the facial nerve supplies signals that control things like eye and mouth movement.

A number of lymph nodes are located in and around the parotid gland as well.

Structure

The parotid gland itself is wrapped in a layer of connective tissue and is shaped like an inverted pyramid. It is a serous gland, containing a plasma-like fluid that is rich in enzymes. The gland itself is yellowish and irregular-shaped.

The lateral part of the gland—the area that is closest to the surface of the skin—is covered with lymph nodes, and the interior surface is grooved and meets with the jaw and masseter muscle.

Fatty tissue and the facial nerve run between the two lobes of the parotid gland, which opens in the mouth near the second maxillary molar. This opening is known as the parotid duct, or Stensen's duct.

Function

The primary function of the parotid gland is the creation of saliva. It's the saliva itself that performs a number of crucial functions. Saliva is a hypotonic solution created through a joint effort by all the salivary glands. It contains electrolytes, macromolecules, and enzymes.

Saliva has a number of important roles in the body:

• Provides lubrication for the mouth.
• Assists in mastication (chewing).
• Aids in swallowing, speaking, and digesting.
• Helps break down food for digestion. The enzyme amylase is particularly important for breaking down carbohydrates.
• Prevents infection in the mouth and throat.
• Helps prevent dental caries (cavities).

When the parotid glands malfunction or stop working, the flow of saliva is decreased and can cause a host of problems.

Associated Conditions

There are a number of conditions or problems that can impact the health and function of the parotid gland. Since the gland contributes to important overall functions of the body, any problems with this gland can spell trouble for the entire system.

Parotid Gland Tumors

Tumors can grow in either lobe of the parotid gland. While these are usually not cancerous, cancerous tumors can affect the parotid gland.

Removal is the required treatment in either scenario, as these tumors can impact the function of the parotid gland and cause swelling in the face and jaw. While this swelling isn't usually painful, it can cause numbness and even loss of facial movement.

Parotid Gland Cancer

When tumors in the parotid gland are cancerous, they require removal and often additional treatment, as well. The close relationship of the parotid glands to the lymph system means cancer can spread easily from this location, so radiation and chemotherapy may be required if a tumor is cancerous.

Parotidectomy

When tumors are removed from the parotid gland, this surgery is called a parotidectomy. A superficial parotidectomy involves the removal of all or part of the superficial—outer—lobe of the parotid gland. A total parotidectomy involves both the deep and superficial lobes of the gland. Both of these procedures require great precision to avoid damage to the facial nerve.

Sialadenitis

This condition is caused by bacteria, viruses, or obstructions. Salivary flow is decreased, which leads to increased infection, pain, and swelling.

Staphylococcal bacteria and the mumps virus are primary culprits of this condition. It can be treated with oral hydration, warm compresses, antibiotics, and sialogogues—medications that increase saliva.

Sialolithiasis

This condition occurs when a stone or other small particle becomes lodged in the salivary duct. It is the most common cause of salivary gland disease and disorders.

The result of these blockages is painful swelling, often during and after eating. Surgical removal of the duct is often required, and medications like sialogogues can be used to help restore the flow of saliva.

Tests

The first step in diagnosing any condition, including those of the parotid gland, is a thorough physical exam. There are a number of other tests or exams that may also be required to determine the size, extent, and seriousness of any conditions that affect the parotid gland.

Here are a few tests your healthcare provider may want to perform if they suspect you are having a problem with your parotid gland:

• Physical examination, including palpating your head and neck
• A biopsy to collect cells or fluid from your parotid gland, done with a fine needle inserted directly into the gland
• Imaging tests like an ultrasound, computerized tomography (CT), or magnetic resonance imaging (MRI) to better visualize the structure and function of your parotid gland