Here's the breakdown:
* θ - the "th" sound at the beginning
* r - the "r" sound in the middle
* u - the "oo" sound
* ː - the long vowel sound
* /ˈ/ - the stress mark
It's important to remember that phonemes are the smallest units of sound in a language, not letters. So, although the word "through" is spelled with 7 letters, it only has 5 distinct sounds.