The retromandibular vein (temporomaxillary vein, posterior facial vein), formed by the union of the superficial temporal and maxillary veins, descends in the substance of the parotid gland, superficial to the external carotid artery but beneath the facial nerve, between the ramus of the mandible and the sternocleidomastoideus muscle.Lateral head anatomy detail The retromandibular vein (temporomaxillary vein, posterior facial vein), formed by the union of the superficial temporal and maxillary veins, descends in the substance of the parotid gland, superficial to the external carotid artery but beneath the facial nerve, between the ramus of the mandible and the sternocleidomastoideus muscle.