Perineal fallout and the shedding of skin cells are the reasons for pants instead of skirts. You are really supposed to wear ankle cuffs on the pants but most just use straight legged pants. You should not go sockless either.
All staff members should wear long sleeved tops/jackets unless they are scrubbing in, and then only take the jacket off right before they scrub. This is because of skin cell fallout.
Think of putting glitter on your arms and opening a sterile item onto the sterile field. The glitter would go flying onto the sterile field. Well, skin cells do the same thing, only you cannot see them.
If you do wear dresses, make sure you have panty hose on with them.