Just for perspective: I am a man in my mid-40s and for as long as i can remember i had this question… is it normal that i can shut my nose close just with some muscles?
I always wondered why some people hold their nose shut with their fingers while jumping into a pool or when exposed to some horrible smell… i never had this need. Changing my sons diapers? No problem! Cleaning the latrines while in the army? Just a breeze!
Ehm… yeah… just thought about this…
How else do people blow out birthday candles, and blow up balloons? The air could just escape through the nose!
I think with diving and other situations is to prevent the exposure of the inside of the nose. Especially when jumping in the water and and pressure can be much higher.
From what i know, there are two ways to close your nose. one is via the soft palate. probably everyone can do that.
the other is via the musculis nasalis, which op probably meant. most people can’t do that.