Does dirt under the nails prevent the validity of ablution?

Nails must be trimmed before forty nights pass, as the Prophet, peace and blessings be upon him, set a time limit in Sahih Muslim that nails, pubic hair, armpit hair, and mustache should not be left untrimmed for more than forty nights. Therefore, men and women must observe this matter. Wudu (ablution) is valid even with a slight amount of dirt under the nail, as it is excused.