Final answer:
Scar tissue lacks hair and melanin, the pigment responsible for skin and hair color. Hair follicles and sweat glands also do not regenerate in scar tissue because it is composed primarily of a dense collagen matrix that prohibits the reformation of these structures.
Step-by-step explanation:
Scar tissue is known to lack hair and melanin production, which are typically found in unaffected skin. This lack of melanin can result in a scar having a different color compared to the surrounding skin. Hair follicles and sweat glands, which are considered accessory structures of the skin, also do not regenerate in scar tissue. Therefore, the scarred area does not grow hair and does not have the same ability to sweat as normal skin.
This is because fibroblasts, which are responsible for generating scar tissue, produce a dense basket-weave pattern of collagen fibers that does not support the reformation of these structures. Moreover, scars and keloids represent an alteration from the original skin structure and texture due to the healing process and are fibrous rather than truly regenerative of the skin's complex architecture, further explaining their lack of hair and melanin.