If you watch or place your fingers on your larynx when you swallow, you'll feel it move up & when you yawn, you'll feel it move down...
Now when you sing, ideally, most of the action should take place within your larynx & you should have a neutral, relaxed larynx & throat doing it's thing automatically.
Try looking in the mirror or place your fingers on your larynx as you sing some scales & a song. Does your larynx shoot up when you sing higher notes?
If it does, I bet those higher notes feel strained & uncomfortable & I bet you have unwanted breaks in your voice...
...Am I right?
If this is the case for you, this is what's happening.
You're trying to control your voice via the muscles that come into play when you swallow.
When you swallow, not only does your larynx shoot up but your constrictor muscles also squeeze, reducing the diameter of your pharynx.
Not only does a high larynx position impair the ability of the muscles & cartilages within the larynx but the tense muscles within your throat reduce your resonance & dull your tone. Your brain then interprets this as a blockage & responds by automatically increasing your air flow to try & remove the blockage. To withstand this extra air pressure, the vocal cords have to tense...
...The result of a high larynx position when you sing is a strained, dull, painful, uncomfortable sounding voice which can cause damage to your vocal cords.
