submandibular lymph nodes. 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.ccasionally 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.