As skin cells move towards the surface, what happens to their nutrient supply?

As skin cells migrate towards the surface of the skin, their nutrient supply becomes poorer, which ultimately leads to cell death. This process occurs because the outer layers of the skin, known as the epidermis, are avascular; that is, they do not contain blood vessels. Nutrients are transported to the deeper layers of the skin where the living cells are located. As cells move upward through the epidermis, they are increasingly distanced from their blood supply, leading to a gradual decline in available nutrients. Consequently, these cells undergo a process called keratinization, where instead of thriving, they eventually die and form a protective barrier made primarily of keratin, which is the main protein in the skin. This transition is essential for maintaining healthy skin, providing a tough, protective outer layer while also allowing for the shedding and renewal of skin cells.