Final answer:
The syllable with the primary accent in the word 'myometrium' is 'tri'.
Step-by-step explanation:
The primary accent in the word 'myometrium' falls on the third syllable, which is 'tr'. The syllables in this word are divided as follows: my-o-me-tri-um. The primary accent or stress is placed on the syllable 'tri', making it the syllable with the primary accent.