Final answer:
It takes approximately 48 days for cells to move from the stratum basale to the surface of the skin, during which time they differentiate into keratinocytes and contribute to the protective keratin barrier.
Step-by-step explanation:
The journey from the stratum basale to the skin's surface involves the migration of skin cells through the different layers of the epidermis. Starting as basal cells, they undergo mitosis and differentiate into keratinocytes, eventually reaching the stratum corneum.
It takes about 48 days for these cells to progress from the stratum basale to the surface, where they form a protective keratin barrier and are ultimately shed. This turnover rate is an average value and can be influenced by several factors including age, health, and environmental exposure.