The submandibular gland is one of the three major salivary glands found in the humans. The other two are the parotid gland and the sublingual salivary glands. Submandibular glands were previously known as ‘submaxillary glands’.
Location and structure of the Submandibular Gland
The submandibular gland is located in an area beneath the floor of the mouth. These glands are two in numbers and are often referred to as a ‘pair of wall-nut sized’ glands. The saliva they secret is both “serous” and “mucous” in nature. The submandibular gland itself weighs roughly between 7-15 gms.
Anatomically speaking, the submandibular salivary gland is located in the submandibular space in the digastric triangle, otherwise known as the submandibular triangle, formed by anterior and posterior bellies of the digastric muscle and inferior margin of the mandible.
This gland is wedged between the body of the mandible and extends up to the digastric muscle inferiorly. Superiorly the gland is bounded by the mylohyoid muscle and anteroposteriorly the body of the mandible.
The Shape of the Gland
Roughly the submandibular gland can be described as a “J-shaped” gland. The mylohyoid muscle divides the submandibular gland into two parts or lobes. The superficial part, or the superficial lobe, and the deep part, or the deep lobe.
The superficial part is the larger of the two. Both these parts or lobes are connected around the posterior border of the mylohyoid muscle.
Submandibular Gland Surfaces
The gland has four surfaces. They are as follows.
(1) Inferior surface
(2) Medial surface
(3) Lateral surface
(4) Posterior surface
The submandibular duct is also called the Wharton’s duct. The Wharton’s duct starts from the deep part of this salivary gland. The submandibular duct is about 2–4 mm in diameter and 5 cm in length.
Clinical Importance of the Submandibular Gland
The submandibular salivary glands are responsible for the production of more than 60% of (resting) saliva in the mouth. So their preservation is very important for humans.
The submandibular gland and the duct are more prone to retrograde infection by the oral flora than any other salivary glands in the mouth. That’s because both the gland and the duct are placed at a lower level to the oral cavity. But normally such a retrograde flow is limited by the constricted ‘punctum’ of the gland.
The occurrence of salivary stones is most common in the submandibular duct and the glands. It is because of the long and tortuous course of the duct, which leads to the stagnation of the saliva in the duct.
The sharp bend present at the posterior part of the duct also increases the chances of sialolith formation. And it’s these sialoliths which commonly result in the resection of the submandibular gland.
During Neck Dissection
The submandibular gland is commonly excised during the procedure of neck dissection. This is quite strange considering the fact that the submandibular glands don’t contain any nodes.
The neck dissection is a surgical procedure done for controlling the neck lymph node metastasis which may happen in cases of squamous cell carcinoma (SCC) of the head and neck. The main purpose of this procedure is to remove the lymph nodes from the side of the neck into which cancer cells may have migrated or metastasized.
During the excision of this gland, the incision is usually taken 5 cm below the angle of the jaw. This is done to avoid any injury to the marginal mandibular branch of the facial nerve which is present in the region.