Lymphatic Drainage of Mouth and Pharynx
Lymphatic fluid, carried by the lymphatic capillaries in the tissues of the mouth and pharynx, is all eventually taken by the lymphatic vessels, either directly or with the interruption by interposed lymph nodes, to the chain of lymph nodes lying along the internal jugular vein. The efferent vessels from these nodes enter into the formation of the jugular lymphatic trunk, which, characteristically, on the left side empties into the thoracic duct near its termination and on the right side into the right lymphatic duct. The thoracic duct and the right lymphatic duct pour their lymph into the bloodstream at the junction of the internal jugular and subclavian veins on the respective side. On either side the jugular trunk may empty directly into the veins near this site.
A more specific description of the lymph nodes involved in the lymphatic drainage of the mouth and pharynx is necessary because of their importance in the metastasis of cancer and the significance attached to the enlargement of a node when an infection occurs in its area of drainage. However, any specific description of lymph nodes is complicated by the facts that lymphatics are quite variable and are difficult or impossible to see in dissection when they are not pathologically conspicuous and that the grouping of the nodes is at best arbitrary and, to quite an extent, artificial. Because of this, descriptions of lymphatics vary greatly, and many different names have been employed for individual nodes and groups of nodes. The number of groups of nodes described for any region can, of course, differ, depending on whether certain nodes are interpreted as forming a separate group or are considered as subsidiaries of another group.
The grouping of the nodes of the head and neck can be described briefly as follows: A pericervical collar of nodes is located at the general region of the junction of the head and neck. From the midline posteriorly to the midline anteriorly, the groups encountered, in order, are occipital, mastoid, parotid, submandibular, and submental nodes. A group of nodes superficial to the sternocleidomastoid muscle and in close relation to the external jugular vein is called the superficial cervical group of nodes; however, some consider them to be an extension of the parotid group. The majority of the groups of nodes not included in the “collar” just described run more or less vertically in the neck. Minor chains of nodes lie along the anterior jugular vein and the spinal accessory nerve, and a major chain of nodes accompanies the internal jugular vein along its entire length. The latter is most commonly designated as the deep cervical group of nodes and is often divided into superior deep cervical nodes superior to the point at which the omohyoid muscle crosses the internal jugular vein and the inferior deep cervical nodes inferior to this point. The retropharyngeal nodes may be an expansion of the superior portion of the superior deep cervical group or a separate group of nodes located between the superolateral part of the pharynx and the prevertebral fascia. Individual nodes are encountered constantly enough in two locations in the superior deep cervical chain that they have merited special naming. A jugulodigastric node is located between the angle of the mandible and the anterior border of the sternocleidomastoid muscle, at about the level of the greater horn of the hyoid bone and between the posterior belly of the digastric muscle and the internal jugular vein. This node receives lymph from the area of the palatine tonsil, tongue, and teeth. A juguloomohyoid node, usually considered as the lowest node of the superior deep cervical group, lies immediately superior to the intermediate tendon or the inferior belly of the omohyoid muscle and may project beyond the posterior border of the sternocleidomastoid muscle. This node receives some vessels directly from the tongue in addition to its other afferents. A subparotid node just inferior to the parotid gland is specially named by some authors. The inferior deep cervical nodes, also called supraclavicular nodes, extend into the posterior triangle of the neck, send expansions along the trans- verse cervical and transverse scapular veins, and inter-mingle with the subclavian and apical axillary lymph nodes. In addition to the groups of nodes described above, some scattered nodes, part of which are often called anterior deep cervical nodes, pertain to the larynx, trachea, esophagus, and thyroid gland.
The groups of nodes specifically involved in the drainage of lymph from specific portions of the mouth and pharynx are indicated briefly in the following statements: The lips have cutaneous and mucosal plexuses from which the lymph drains to the submandibular, submental, and (to a slight extent) superficial cervical groups. Lymph from the central part of the lower lip first drains to the submental nodes. Lymph from the cheek travels mostly to the submandibular nodes but also to superficial cervical nodes and, in part, directly to superior deep cervical nodes. From the anterior part of the floor of the mouth, drainage is, in part, directly to the lower of the superior deep cervical group and, in part, to the submental and submandibular nodes. The posterior part drains to submandibular and superior deep cervical nodes. Lymph from the hard and soft palates may travel directly to superior deep cervical nodes (near the digastric muscle) or to submandibular nodes or, particularly from the soft palate, to retropharyngeal nodes. The lymphatics of the teeth anastomose with those of the gums. Lymph from the superomedial alveolar processes drains similarly to the palate, whereas lymph from the inferomedial alveolar processes drains similarly to the floor of the mouth. Drainage from the lateral alveolar processes is similar to that of the lips and cheek. The jugulodigastric node, or at least a node in that area, may be enlarged when a tooth, particularly in the molar region, is infected. The lymphatic drainage of the tongue goes either directly or indirectly to the superior deep cervical nodes, and, in general, the farther forward the area on the tongue, the lower in the deep cervical chain is the related node. Four sets of collecting vessels of the tongue are described: apical vessels lead to submental nodes and the juguloomohyoid node; marginal vessels to superior deep cervical nodes and perhaps submandibular nodes; basal vessels to superior deep cervical nodes (chiefly, the jugulodigastric node); and central vessels mostly to superior deep cervical nodes, with a few to submandibular nodes. The central vessels from each side of the tongue go to both right and left superior deep cervical nodes. No vessels from the tongue are said to reach any of the more superficial nodes. Drainage from the large salivary glands is much as would be expected: parotid gland to parotid nodes (some of which are described as being in the substance of the gland); submandibular gland, in part to submandibular nodes but mostly to superior deep cervical nodes; and sublingual gland, much like that of the submandibular gland. Part of the lymph from the area of the palatine tonsil goes to the superior deep cervical nodes and much of it to the jugulodigastric node. The mucosa of the pharynx is rich in lymphatics, and the drainage from the roof and upper part of the posterior wall is to the retropharyngeal nodes. The collecting vessels of the laryngeal pharynx gather in the wall of the piriform sinus, pierce the thyrohyoid membrane, and continue to nearby superior deep cervical nodes.