The submandibular lymph nodes sit between the submandibular salivary glands, which are underneath the tongue, and the mandible, or lower jawbone. Occasionally one or more of the lymph nodes may be embedded deep within the salivary gland.
The lymphatic system is part of the immune system, which helps the body fight diseases and other harmful agents. Lymph nodes act as points of filtration and cell multiplication within this system. They filter the lymphatic fluid of unwanted debris and bacteria and serve as early warning devices for the presence of infection.
The submandibular nodes are small, usually measuring approximately 1 centimeter in a healthy adult. The submandibular duct, which brings lymph fluid to the node, is approximately 5 to 6 centimeters long in the average adult. The wall of the duct is thin and flexible. As the duct runs forward, it passes between the sublingual gland and genioglossus (the primary muscle of the tongue) to create an opening in the floor of the mouth. As the duct travels through the deepest part of the submandibular gland, it connects with tributaries draining into the lobe.
The arterial blood supply to the submandibular nodes arises from multiple parts of the facial and lingual arteries. Venous blood drains into the deep lingual vein. These lymph nodes filter lymph from the submaxillary (salivary) gland, tongue, mouth, lips, cheek, nose and conjunctiva (the membrane that covers the eyeball and underside of the eyelid).
Swollen submandibular nodes usually indicate an active viral or bacterial infection and are commonly associated with infections of the sinuses, eyes, and ears.