Venous Drainage of Mouth and Pharynx
As elsewhere in the body, the veins of the face, oral cavity, and pharynx are more variable than are the arteries. The veins in this region tend to lie more superficially than the arteries and form plexuses substituting for single, definite vessels.
The internal jugular vein eventually receives almost all of the blood derived from the mouth and pharynx. This vein begins as a continuation of the sigmoid sinus at the jugular foramen and descends in the neck lateral to the internal and then common carotid arteries to about the level of the sternoclavicular joint, where it joins the subclavian vein to form the brachiocephalic vein.
For the most part, the arteries described in the previous section have veins of the same name accompanying them, but the veins into which these drain differ in various ways from the branches of the external carotid artery. The superior thyroid vein does not differ greatly from the superior thyroid artery, but it does usually empty directly into the internal jugular vein. Frequently, one encounters a middle thyroid vein with no corresponding artery that also empties into the internal jugular vein.
The deep lingual vein, often more than one channel, accompanies the corresponding artery from the tip of the tongue to the anterior border of the hyoglossus muscle, where the major vein receives the sublingual vein and then accompanies the hypoglossal nerve on the lateral surface of the hyoglossus muscle, as well as a smaller vein(s) that runs alongside the lingual artery. Near the posterior border of the hyoglossus muscle, one of these veins receives the dorsal lingual veins, and then they either join to form a short lingual vein or continue separately to empty either into the common facial vein or directly into the internal jugular vein.
The facial vein follows a not-so-tortuous path (compared with the artery) from the medial angle of the eye to the lower border of the mandible near the anterior margin of the masseter muscle. From here it courses posteriorly in the submandibular triangle (not as sheltered by the mandible as the artery) to join the anterior division of the retromandibular vein in the formation of a common trunk that empties into the internal jugular vein. The anterior facial vein receives tributaries corresponding mostly to the branches of the facial artery but also some communications from the pterygoid plexus, one of which is often called the deep facial or external palatine vein.
The maxillary vein is sometimes a distinct vein with tributaries corresponding to the artery, but more commonly appears as one or more short veins that drain the pterygoid plexus and join the superficial temporal vein in the formation of the retromandibular vein. The pterygoid plexus is partly superficial and partly deep to the lateral pterygoid muscle. The tributaries are those veins that correspond to the branches of the maxillary artery, and the plexus communicates with the cavernous sinus by small veins passing through the foramina in the floor of the middle cranial fossa and with the pharyngeal plexus, in addition to the other connections previously mentioned.
The bulk of a pharyngeal plexus of veins lies superficial to the pharyngeal constrictor muscles. This plexus communicates in all directions, with connections to the internal and external jugular veins, pterygoid plexus, common facial vein, lingual vein, superior thyroid vein, and a submucosal plexus, which is best developed in the lower part of the posterior pharyngeal wall.
The posterior division of the retromandibular vein joins the posterior auricular vein to form the external jugular vein, and an anterior jugular vein begins in the chin superficial to the mylohyoid muscle and courses inferiorly and then laterally to empty into the external jugular vein.