Updated 13th of March 2022
The sublingual gland is one of the three major salivary glands in the human mouth. Those are the parotid glands, the submandibular glands, and the sublingual glands, each one present in pairs. Salivary glands produce either serous type of saliva (watery fluid), mucous (thick and slippery fluid), or seromucous (a mix of both).
The mouth also has hundreds of minor salivary glands located all over, and their secretion is mainly mucous.
The sublingual glands are the smallest of the major salivary glands, and they provide 3 to 5 % of the total saliva volume, producing predominately mucous saliva.
Sublingual glands are called this way because they are located underneath the tongue, below the floor of the mouth. They are bordered on the side by the mandible bone, and underneath by the mylohyoid muscle (the neck muscle that runs from the mandible to the hyoid bone). They have an oval, almond shape and each has 8 to 30 minor glands around it.
The sublingual glands can be felt behind each lower canine tooth. The index finger can palpate a gland by compressing this area.
The ducts of Rivinus are a group of 8 to 20 excretory ducts that drain the sublingual gland. The largest of all, the sublingual duct of Bartholin, joins the submandibular duct of Wharton to drain through the sublingual caruncle. The sublingual caruncle is a papilla located between to the sublingual gland and the lingual frenulum. Most of the remaining small sublingual ducts of Rivinus come out separately into the mouth also near the lingual frenulum.
Anomalies and disease
Salivary glands are subject to several disorders, with the major one being the ranula. Cancers are less common, and they comprise of 3% to 4% of all head and neck tumours.
A ranula is a type of mucocele (swelling caused by a mucous retention cyst) that occurs under the tongue. Ranulas are the most common disorder associated with the sublingual glands because the secreted saliva has a higher content in mucin (a molecule that forms mucus) compared to other salivary glands.
Ranulas are mostly caused by trauma to the delicate sublingual gland ducts. When those ducts rupture, the evacuated mucin forms a cyst within the surrounding connective tissues area. To be more precise, ranulas are pseudocysts, and the difference with cysts is that they don’t have epithelial lining of their wall (a kind of containing membrane).
Ranulas need no treatment if they are small and asymptomatic. But if they grow too large and cause pain and dysphagia (difficulty of swallowing), it would be recommended to remove them surgically.
Sometimes mucin from the gland or ducts can accumulate under the mylohyoid muscle and cause swelling in the neck. In this case it is referred to a cervical ranula.
Sialolithiasis (salivary stones, sialoliths, or calculi), are small stones that form and block the saliva flow in the ducts. They are also a common salivary gland disease, and by blocking the flow of saliva, the stones can cause discomfort and pain.
Sialoliths can be diagnosed by palpating manually or by ultrasound with CT or MR sialography (radiographic examination of the salivary glands).
Although salivary stones mainly impact the submandibular gland, they may also occur in the sublingual gland. Salivary stones rarely need treatment other than the conservative ones, which consist of drinking more water and using sialagogues (drugs that promote the secretion of saliva). If conservative treatments fail and symptoms persist, surgery may be recommended.
Salivary gland inflammation
Sialadenitis refers to salivary gland inflammation and may be caused by bacterial or viral infection. The inflammation of a salivary gland may be followed by fever, pain, and swelling. If the cause of sialadenitis is a bacterial infection, then antibiotics are recommended. If the cause is viral, then it’s advised to drink lots of water and take sialagogues (drugs that stimulate the production of saliva).
Surgery is only recommended if an abscess complicates the infection. Surgery consists of either draining the salivary gland, or the partial or its total excision.
When the salivary gland inflammation becomes chronic, it can be related to autoimmune conditions (like the Sjogren’s syndrome), or to radiation exposure. If there is a long-term loss of function of salivary glands, regenerative therapy can help restore the production of saliva.
Salivary gland cancers
Of all head and neck cancers, 3% to 4% of them involve the salivary glands, including the sublingual gland. In general, the larger the size of the gland, the higher the odds of a mass being benign.
Adenoid cystic carcinoma and mucoepidermoid carcinoma are the most common sublingual gland malignancies. Mucoepidermoid carcinomas are mostly common in the parotid glands, and they are usually low grade, but can also be intermediate or high grade. Adenoid cystic carcinoma is usually slow growing and often appears to be low-grade, but it’s very hard to get rid of completely because it tends to spread along nerves.
Most tumors have no pain or symptoms, making them difficult to diagnose. The treatments of salivary gland cancers include surgical tumor removal and radiation therapy.
- Yi Sui, Siqi Zhang, Yongliang Li, Xin Zhang, Waner Hu, Yanrui Feng, Jingwei Xiong, Yuanyuan Zhang & Shicheng Wei. (Generation of functional salivary gland tissue from human submandibular gland stem/progenitor cells). Stem Cell Research & Therapy volume 11, Article number: 127 (2020).
- Kessler AT, Bhatt AA. (Review of the Major and Minor Salivary Glands, Part 1: Anatomy, Infectious, and Inflammatory Processes). J Clin Imaging Sci. 2018;8:47.
- Holmberg KV, Hoffman MP. (Anatomy, biogenesis and regeneration of salivary glands). Monogr Oral Sci. 2014;24:1-13.
- Jeewanjot S. Grewal; Bruno Bordoni; Jamie Shah; Jesse Ryan. (Anatomy, Head and Neck, Sublingual Gland). StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
- TeachMe Anatomy, (The Sublingual Gland).
- Wikipedia, (Sublingual gland).
- Medical News Today, (What to know about salivary stones).
- Cleveland Clinic, (Sialadenitis (Swollen Salivary Gland)).
- Comprehensive ENT, Head & Neck Surgery PC, (Salivary Gland Surgery).
- American Cancer Society, (What Is Salivary Gland Cancer).