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10.05: Zone M3 – Superior Posterior Cheek

YOUR ASSIGNMENT FOR THIS LESSON

✅ Step #1: Review all content below.

✅ Step #2: Image the M3 zone on your own with your ultrasound, and using the checklist provided on this page, check off all key structures to be identified in this location

TRANSDUCER POSITION AT M3

Note: Clip is sped up.

STANDARD M3 ORIENTATION:
TRANSVERSE

The intersection of the vertical line from the lateral canthus to the horizontal line from the lateral commissure is the location of M3.

QUICK TIP
  • First, identify the teeth, which will appear hyperechoic (bright) like bone. Adjust the depth of penetration so the teeth are visible at the bottom of the screen.
  • Next, slide the probe posteriorly until you can visualize the anterior portion of the masseter muscle, as identified in M1 and M2.
  • In the region anterior to the masseter, you will see a hypoechoic (dark) cobblestone-like area, which is the buccal fat pad.
    • Just deep to this fat pad, although it can be hard to see at times, is a hypoechoic linear structure known as the buccinator muscle.

EXAMPLE OF TRANSVERSE IMAGE ACQUIRED AT M3

Standard image acquired at M3. (Transverse| Left side is patient's anterior). See key below for lables.*

ANATOMICAL LEGEND FOR M3 LOCATION IN TRANSVERSE

*Standard image acquired at M2 labeled with key anatomical structures.
Deep Fat Compartments

KEY VESSELS IN THE REGION

DOPPLER IMAGES ACQUIRED AT M3 OF KEY VESSELS

Note: Pay attention to the facial artery and vein at M2. The vein will be more posterior closer to the mandible. The artery will run more anterior.
Play Video
QUICK TIP
  • At M3 it is very possible to see both the facial vein or artery or both simultaneously! 
    • To determine which vessel is which recall that the facial vein is posterior to the facial artery. Track any vessel you see back to M2. There identify both the artery and vein, the most anterior vessel (one furthest from the masseter muscle) will be the facial artery.
  • Both these vessels will run within the buccal fat anterior to the masseter muscle at M3.
    • Generally the artery will be deeper, but do not rely on this to differentiate these vessels!
  • At M3 these are large caliber vessels with higher rates of flow, this makes doppler imaging easy. 

DO IT YOURSELF CHECKLIST

Structures to Identify on Ultrasound for M3

Once you have completed this checklist, mark this part of the lesson as complete.