Updated 1st of May 2022
There are three major salivary glands in the human mouth, the parotid, submandibular and sublingual glands. The submandibular gland is the second largest one, where the parotid gland is the largest, and the sublingual gland is the smallest. Like all major glands, the submandibular glands exist in pairs. They are located beneath the floor of the mouth.
Historically called the submaxillary glands, the submandibular glands produce saliva. This helps keeping moisture inside the mouth and to lubricate the food as it’s where digestion starts. The saliva secreted by all salivary glands also have a role in tooth decay prevention.
The submandibular glands are divided into two lobes, the superficial lobe (largest) and the deep lobes (smallest). The two lobes are separated by the mylohyoid muscle. They are located under the floor of the mouth and over the digastric muscles, in a region called the submandibular triangle. This triangle is formed by two belies of the digastric muscle, and the inferior margin of the mandible.
The submandibular gland’s main excretory duct is called submandibular duct or Wharton duct. Its size is approximately 5 cm in length and 1.5mm in diameter. It leads to the oral cavity at the sublingual caruncle (or caruncula). The caruncle is a structure located in the floor of the mouth and is on either side of the lingual frenulum.
The gland can be felt by placing a finger inside the mouth and under the tongue at the posterior region.
The gland unit that produces saliva is called adenomeres, and each one contains an acinus (plural: acini). An acinus is a cluster of cells that resembles lobes in a berry. Each acinus is made of cells that produce either serous or mucous saliva. An acinus also has its own mini duct.
Like all salivary glands, the submandibular gland produces saliva in the oral cavity. This moistens the food inside the mouth to start digestion by chewing and swallowing. Saliva also has a role in keeping the mouth and the teeth clean as it neutralizes and washes out bacteria.
When not stimulated, which means when there are no objects/foods in the mouth, the submandibular glands provide most of the saliva in the mouth. But when stimulated, which means that food is inserted in the mouth, the parotid glands take over, producing most of the saliva that helps digestion.
Anomalies and diseases
Submandibular glands usually function without problems. But like other salivary glands, they are subject to several conditions and disorders. Cancers are less common, and they comprise of 3% to 4% of all head and neck tumours.
Sialolithiasis (salivary stones, sialoliths, or calculi), are tiny stones that form and block the saliva flow in the ducts. This condition may induce the submandibular gland to become swollen, causing discomfort and pain. Sialolithiasis most affects mostly people aged 30 to 60, and they are more common in men than in women.
Sialolithiasis can be found in any of the salivary glands, but mostly (80%) in the submandibular glands. The definitive cause of salivary stones is unknown, but they are associated with some factors, including dehydration, mouth trauma, smoking, and periodontal disease (gum disease).
Sialoliths can be diagnosed by palpating manually or by ultrasound with CT or MR sialography (radiographic examination of the salivary glands).
Salivary stones rarely need treatment other than drinking more water and using sialagogues (drugs that promote the secretion of saliva). If conservative treatments fail and symptoms persist, surgery may be recommended to prevent complications and infection.
Sialadenitis is an infection of a salivary gland, which most often affects the parotid and the submandibular glands. Those infections may be caused by bacteria (Staphylococcus aureus), or viruses, such as mumps.
Sialadenitis are more likely to occur when there is a blockage in the gland from a stone, dehydration, or from Sjögren’s syndrome, an autoimmune disorder that affects the glands. Symptoms of salivary gland infections may include pain and swelling around the affected gland, fever, and pus that oozes from the gland.
Sjögren’s syndrome is an autoimmune disorder that reduces moisture produced by the glands of the eyes and mouth. It is named after Henrik Sjögren, a Swedish eye healthcare provider who discovered the condition.
Sjögren’s syndrome may be primary or secondary. Primary Sjögren’s syndrome develops on its own, and secondary Sjögren’s syndrome in conjunction with other autoimmune diseases, such as rheumatoid arthritis and lupus. While Sjögren’s syndrome can affect any sex, females are nine times more likely to be affected than males.
The cause of Sjögren’s syndrome is unknown. But genetics, reproductive hormones, environmental factors, and infections may be associated with the development of this disease.
The most common symptoms of Sjögren’s syndrome are dry eyes and dry mouth, as well as muscle and joint pain. Other symptoms may include an abnormal taste in the mouth, a burning sensation in the eyes, blurry vision, trouble chewing or swallowing, cough, enlarged salivary glands, tooth decay, and vaginal dryness.
Treatment for Sjogren’s syndrome may be limited to managing the dry eye and dry mouth by using over the counter eyedrops and sipping water more frequently. But in most severe cases, some people need prescription medications, or even surgical procedures.
Xerostomia is when there is less saliva in the mouth causing it to feel dry. This happens when salivary glands are in a hypofunction (underperformance) state, producing less saliva than normally needed.
Dry mouth may be caused by side effects from numerous medications, infections, autoimmune disease, systemic diseases like diabetes, or cancer treatments like chemotherapy. Symptoms of xerostomia include the sensation of having dry mouth, difficulty chewing and swallowing, sore throat, cracked lips, mouth sores, and bad breath.
Salivary gland cancers
Of all head and neck cancers, 3% to 4% of them involve the salivary glands. Most of them are benign and they can be removed by surgery. There are a few malignant cancerous tumors of the salivary glands.
Mucoepidermoid carcinomas are the most common cancer of the salivary glands. They mostly occur in the parotid glands but can also be found in the submandibular glands.
Adenoid cystic carcinoma is a usually slow growing cancer and often appears to be low-grade, but it’s very hard to get rid of completely because it tends to spread along nerves. The outlook is best for those with smaller tumors.
Adenocarcinomas are tumors that start in the gland cells. This type of cancer has many types, including acinic cell carcinoma, polymorphous low-grade adenocarcinoma (PLGA), and other rare types of adenocarcinomas.
Salivary gland cancers can also manifest as mixed tumors, affecting multiple tissue types. These may include pleomorphic adenomas, carcinosarcoma, and metastasizing mixed tumor.
Most tumors have no symptoms or pain, which makes them difficult to detect. The most common treatments for salivary gland cancers include surgical removal and radiation therapy.
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- Medical News Today, (What to know about salivary stones).
- Comprehensive ENT, Head & Neck Surgery PC, (Salivary Gland Surgery).
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- KenHub, (Submandibular triangle).
- Verywell Health, (Anatomy of the Submandibular Gland).