Orris

Stenson's duct runs parallel to masseter or over it ?

Reading File
Finding Sources
The textbooks are unanimous. Here is the definitive answer:

Stensen's Duct and the Masseter

Stensen's duct (parotid duct) runs over (across the external/anterior surface of) the masseter muscle - not merely parallel to it.

Course in detail

  1. The duct exits from the anterior border of the parotid gland at roughly the level of the tragus.
  2. It travels across the external/superficial surface of the masseter, running roughly parallel to the zygomatic arch (about 1 finger-breadth below it).
  3. At the anterior border of the masseter, it turns sharply medially (deeply).
  4. It then pierces the buccinator muscle obliquely.
  5. Finally it opens into the oral cavity opposite the upper second molar tooth.

Why the confusion?

The duct does run in a direction that is parallel to the zygomatic arch as it crosses the masseter, which sometimes gets misread as "parallel to the masseter." But its relationship to the masseter itself is one of superficial crossing (running over it), not running alongside it.

Sources

  • Gray's Anatomy for Students - "The parotid duct passes anteriorly across the external surface of the masseter muscle and then turns medially."
  • Bailey and Love's Short Practice of Surgery - "The parotid (Stensen's) duct passes over the masseter muscle and enters..."
  • Color Atlas of Human Anatomy Vol. 2 - "passes parallel to the zygomatic arch over the masseter."
  • Scott-Brown's Otorhinolaryngology - "travels across the masseter muscle...turns medially at the anterior border of the masseter."
So the correct answer: Stensen's duct runs OVER the masseter (across its superficial surface). It runs parallel to the zygomatic arch, not to the masseter itself.
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