The Major Lips
A woman's major lips (the outer lips of the vulva) respond differently, depending on whether she has given birth to children or not. If she has not given birth, sexual excitement will cause her major lips to flatten out and expose the vaginal opening. The major lips of a woman who has given birth, on the other hand, are rather large and now grow even larger as a result of engorgement. Nevertheless, they also expose the vaginal opening.

The Minor Lips
The minor lips (the inner lips of the vulva) swell considerably in all women and also change their color to a progressively deeper red. The clitoris (just as the penis) increases in size as its erectile tissue becomes filled with blood. This increase is usually most noticeable in the diameter of the clitoral shaft.