The submandibular glands, previously called submaxillary glands, are major salivary glands located under the floor of the mouth. In adults, each gland weighs about 15 grams. They produce 60–67% of the saliva when the mouth is at rest. When you eat or stimulate saliva, their contribution decreases, and the parotid glands take over, producing around 50% of saliva.
Anatomy and Structure of the Submandibular Gland
Each gland divides into two main lobes and has a complex network of ducts, cells, and blood vessels.
Lobes of the Gland
The submandibular gland is divided into two main sections, or lobes, each with a specific location and function in saliva production.
- Superficial lobe: This is the larger part of the gland and sits above the mylohyoid muscle.
- Deep lobe: Smaller and located beneath the mylohyoid muscle.
- Duct system: The gland releases saliva into the submandibular (Wharton) duct, which loops around the back edge of the mylohyoid muscle and travels to the floor of the mouth. It opens at the submandibular duct papilla, a small prominence near the tongue’s frenulum.
Microanatomy
At the microscopic level, the submandibular gland is made up of tiny secretory units and ducts that work together to produce and deliver saliva efficiently.
- Lobes and lobules: Each lobe contains smaller lobules, and each lobule contains secretory units called adenomeres.
- Acini: Adenomeres consist of acini (small clusters of cells).
- Serous cells: Produce watery saliva with digestive enzymes like amylase.
- Mucous cells: Produce mucus to lubricate food.
- Serous demilunes: Some mucous acini are capped by serous cells shaped like a half-moon, which add enzymes to the saliva.
- Ducts: The gland has long striated ducts and short intercalated ducts that carry saliva from the acini to the main duct (Wharton’s duct).
The submandibular gland is classified based on the structure and arrangement of its secretory cells. It is a branched tubuloacinar gland, consisting of multiple branches, with tubules forming each branch; these tubules contain secretory cells. The gland is also a mixed gland, made up of both serous and mucous cells. Although most cells are serous, the saliva it produces is primarily mucous.
Function of Secretory Cells
The secretory cells of the submandibular gland produce saliva that lubricates food and begins the digestion of starches.
- Mucous cells: Produce mucin, which lubricates the food as it travels through the esophagus.
- Serous cells: Produce salivary amylase, which helps break down starches in the mouth.
Together, these cells produce most of the saliva in the mouth. The sublingual and parotid glands contribute the rest.
Blood Supply
The submandibular gland receives blood from nearby arteries, which provide oxygen and nutrients to support its saliva-producing functions.
- Arteries: The submandibular glands get most of their blood from the submental and sublingual arteries, which branch from the facial artery, and from the lingual artery.
- Veins: The gland is drained by the facial and lingual veins.
Lymphatic Drainage
The submandibular gland drains lymph fluid through nearby lymph nodes, which help the body fight infections and support immune health.
- Drains first into the submandibular lymph nodes
- Then flows to the jugulodigastric lymph nodes
Nerve Supply
The submandibular gland’s nerves control saliva production, with parasympathetic nerves increasing flow and sympathetic nerves adjusting its composition.
- Parasympathetic nerves: Increase saliva production. Signals come from the facial nerve via the chorda tympani, which connects with the lingual nerve before reaching the submandibular ganglion.
- Sympathetic nerves: Reduce blood flow to the gland, which lowers saliva volume but increases enzyme content.
Functions of the Submandibular Gland
The submandibular glands are essential for producing saliva and keeping the mouth healthy. Their main functions include:
- Production and secretion of saliva: The glands continuously produce saliva, which helps keep the mouth moist and aids in speaking and swallowing.
- Role in digestion and lubrication: Saliva contains enzymes like amylase that begin breaking down starches in food. It also lubricates food, making it easier to chew and swallow.
- Antimicrobial properties of saliva: Saliva contains substances that help fight bacteria and viruses, protecting the mouth and teeth from infections.
- Contribution to oral pH balance: Saliva helps neutralize acids in the mouth, preventing tooth decay and maintaining a healthy oral environment.
Common Disorders and Conditions of the Submandibular Gland
The submandibular glands can be affected by several conditions, which may cause pain, swelling, or problems with saliva production. Some of the most common issues include:
- Sialolithiasis (Salivary Stones):
Small stones can form in the ducts of the gland, blocking saliva flow. This can cause pain, swelling under the jaw, and difficulty swallowing, especially during meals. - Infections (Sialadenitis):
Bacterial or viral infections can inflame the gland. Symptoms may include tenderness, redness, swelling, fever, and foul-tasting saliva. - Tumors:
Tumors can develop in the submandibular gland and may be benign (non-cancerous) or malignant (cancerous). Warning signs include a persistent lump, swelling, or pain in the gland area. While benign tumors are more common, malignant tumors require prompt medical attention.
Some malignant submandibular gland tumors include:
- Mucoepidermoid carcinoma
- Adenoid cystic carcinoma
- Acinic cell carcinoma
- Adenocarcinoma
Each has different growth patterns and treatment approaches.
- Other Disorders:
- Autoimmune conditions: Diseases like Sjögren’s syndrome can reduce saliva production and cause dry mouth.
- Impact of dehydration or medications: Lack of fluids or certain medications can reduce saliva flow, which makes the mouth dry and increases the risk of infections or difficulty swallowing.
Role of Clinical Trials in Developing New Cancer Therapies
Clinical trials play a vital role in advancing cancer care by testing potential new treatments, improving existing therapies, and identifying safer, more effective options for patients. They help researchers understand how cancers grow and respond to different approaches. Solid tumor clinical trials are one example of ongoing research, focusing on cancers that form masses in organs or glands. Similarly, head and neck cancer clinical trials are helping researchers evaluate new targeted therapies, immunotherapies, and combination treatments for cancers affecting the throat, mouth, and related areas. These trials support the development of more precise and effective treatment strategies.
Through participating in clinical trials, patients can play a key role in advancing cancer treatments and improving outcomes.
Conclusion:
In conclusion, the submandibular glands play a vital role in saliva production, digestion, and oral health. Understanding their structure, function, and potential disorders helps with early diagnosis and timely care. Latest innovations in medical research continue to improve treatment approaches and patient outcomes. Those interested in advancing cancer treatment can participate in ongoing clinical research studies in Nebraska.
Frequently Asked Questions
How to treat a swollen submandibular gland?
Treatment depends on the cause. Mild swelling often improves with good hydration, warm compresses, gentle massage, and saliva-stimulating foods. Doctors may prescribe antibiotics for infections or recommend procedures to remove stones if blockage occurs.
Where is the submandibular gland located?
The submandibular gland sits beneath the lower jaw, under the floor of the mouth, on both sides of the neck.
Can submandibular lymph nodes be cancerous?
Yes, submandibular lymph nodes can become cancerous, but this is uncommon. Persistent swelling, hardness, or painless lumps should be checked by a doctor to rule out cancer or other serious conditions.
