What provides nutrients to living cells in the hair's differentiated zone?

The underlying papilla plays a crucial role in nourishing the hair by providing essential nutrients to the living cells located in the hair's differentiated zone. This structure contains blood vessels that supply the necessary rich supply of blood, oxygen, and nutrients which are vital for hair growth and health. The papilla is situated at the base of the hair follicle and is an integral part of the hair bulb, working in conjunction to ensure that the hair cells receive what they need to thrive and produce strong hair strands.

In this context, while other structures like the dermis and the subcutaneous layer contribute to the overall health of the skin and hair, it is specifically the papilla that is tasked with directly supporting the hair follicle's growth through its blood supply. The hair bulb, while it contains the living cells that differentiate into hair, does not provide the nutrients itself; rather, it is the underlying papilla that facilitates this process.