Complex sentence: Non-keratinised surfaces must be kept moist by bodily secretions to prevent them drying out and dying, whereas keratinised surfaces are protected from abrasion by keratin and kept hydrated and protected from dehydration by glycolipids produced in the stratum granulosum.
Split into simpler sentences: Non-keratinised surfaces must be kept moist by bodily secretions to prevent them drying out and dying. Keratinised surfaces are protected from abrasion by keratin and kept hydrated and protected from dehydration by glycolipids produced in the stratum granulosum.