Why does my glans "flare" out during erections?
The cause of the flaring is the same as what causes the shaft of your penis to get large and stiff during erections. Blood enters the penis faster than it exists, causing the penis to expand like a balloon. It also causes the glans, the end of your penis to balloon as well.
As the skin tightens on the glans, it causes the rough texture of the glans to stand up. Your glans has a lot of nerve endings which are particularly sensitive to touch. The textured skin makes it even more sensitive to touch.
The bottom edge of the glans is called the corona. It flares out during erections for the purpose of sexual intercourse. It causes the glans to come in firm contact with the walls of your wife's vagina. Thus, every movement you or she makes during intercourse, sends feelings of pleasure through your glans and through her vagina and clitoris.