now, that's all nice and gross and stimulating in various ways, but the question remains: why are the nostrils round? - cause your fingers are too - so, why are the fingers round? - 'cause of the friction; to illustrate, imagine a glass of Wodka-Martini ....
Somehow all this visual aide stuff is shite without a nice scary formula to go with it. Show them kids you still know something they don't! and end your short lecture, with "see, it's simple logic."