Final answer:
Hair is unlikely to regrow in an area affected by a third-degree burn because the burn destroys not only the epidermis and the dermis, but also the hair follicles within these layers. Scar tissue that forms during the healing process does not support the regeneration of hair follicles.
Step-by-step explanation:
When a burn on the forearm destroys the epidermis and the deep dermis and then heals, the capacity for hair growth in the affected area can be compromised. If the burn is categorized as a third-degree burn, it extends through the epidermis and dermis and destroys the tissue. This means that not only the skin but also the structures within, like hair follicles, sweat glands, and sebaceous glands, are damaged. Since these accessory structures are responsible for hair growth, their destruction means that hair will most likely not regrow in the area. Scarring usually occurs because the fibroblasts, while repairing by collagen deposition, create a basket-weave pattern of scar tissue which lacks the typical cellular structure of skin, including hair follicles.