Submandibular Gland

The submandibular gland is the second of the three major salivary glands, after the parotid and before the sublingual gland. It is situated both superiorly and inferiorly to the posterior aspect of the mandible in the submandibular triangle of the neck and makes up part of the floor of the oral cavity.

Borders

The mylohyoid muscle runs through the lobules of the gland and sections it off into superficial and deep parts. The superficial portion of the submandibular gland can be seen in the submandibular triangle of the neck and is covered by the investing layer of deep cervical fascia.The deep portion of the submandibular gland is that which limits the inferior aspect of the oral cavity. It lies between the hyoglossus muscle and the mandible. It ends at the posterior border of the sublingual gland.

Histology

This glandular mass is responsible for the production of 70% of the over salivary output. It secretes both serous and mucinous saliva, although the majority of it is serous, with a 3:2 ratio in it’s favor. It’s duct, which connects the gland with the oral cavity proper is known as Wharton’s duct and opens at the lingual papilla, which can be found on either side of the lingual frenulum. It runs along the gland and is approximately four centimeters in length and between two and four millimeters wide.

Blood Supply and Innervation

The facial and lingual arteries contribute to the blood supply of the submandibular gland and in turn their venous drainage is provided by the corresponding veins. The secretory mechanism of the submandibular gland is regulated directly by the parasympathetic nervous system by which it is stimulated and indirectly by the sympathetic nervous system by which it is inhibited. These exact fibers include presynaptic fibers from the facial nerve (CN VII) via the chorda tympani to the submandibular ganglion and postsynaptic fibers from cells in the submandibular ganglion that together make up the parasympathetic secretomotor fibers. The vasoconstrictive sympathetic fibers stir from the superior cervical ganglion.

Pathology

Sialoliths, otherwise more simply known as salivary stones can occur in all of the major salivary glands, but can be seen most frequently in the submandibular gland. Since this is the gland that provides the majority of the salivary product, it stands to reason that the salivary contents are most likely to accumulate within it or its duct if there is an imbalance in the contents of a disruption of the saliva flow. If a stone lodges itself in the salivary duct it can partially or completely occlude the tube, which causes the glands to become painfully congested and swollen. Ultrasonic means are the best way to diagnose a salivary stone and they are easily removed surgically either intra or extra orally. If this phenomenon reoccurs frequently, the gland will be removed and pseudo saliva is prescribed.