Retromandibular vein

The retromandibular vein (temporomaxillary vein, posterior facial vein) is a major vein of the face. It is formed within the parotid gland by the confluence of the maxillary vein, and superficial temporal vein. It descends in the gland and splits into two branches upon emerging from the gland. Its anterior branch then joins the (anterior) facial vein forming the common facial vein, while its posterior branch joins the posterior auricular vein forming the external jugular vein.

Origin
The retromandibular vein is formed within the parotid gland  by the confluence of the maxillary vein, and superficial temporal vein. 

Course
It descends inside parotid gland,  superficial to the external carotid artery (but beneath the facial nerve), between the sternocleidomastoideus muscle and ramus of mandible. It emerges from the parotid gland inferiorly, then immediately divides into two branches: 
 * an anterior branch which passes anterior-ward to unite with the (anterior) facial vein forming the common facial vein (which then empties into the internal jugular vein).
 * a posterior branch which penetrates the investing layer of the deep cervical fascia before  uniting with the posterior auricular vein forming the external jugular vein.

Function
The retromandibular vein provides venous drainage to the superior cranium, and significant drainage to the ear.

Clinical significance
Parrot's sign is a sensation of pain when pressure is applied to the retromandibular region.