Final answer:
Hypopigmentation is a reduction in skin pigment, resulting in lighter patches of skin. This can occur due to various reasons, including skin diseases like vitiligo. Hyperpigmentation is an increase in skin pigment and is associated with conditions like Addison's disease.
Step-by-step explanation:
Hypopigmentation refers to areas of skin where the pigment (melanin) is reduced, resulting in lighter colored patches compared to the surrounding normal skin. This can occur for various reasons such as post-inflammatory processes, genetic conditions like albinism, or skin diseases such as vitiligo. In vitiligo, an autoimmune process targets and destroys melanocytes—the cells responsible for producing melanin—leading to depigmentation and the appearance of lighter skin patches. In contrast, hyperpigmentation involves an increase in skin pigment, as seen with Addison's disease, and results in darkening of the skin.
The skin protects itself from ultraviolet radiation through a tanning response, where it produces additional pigment to absorb future UV exposures, maintaining the health and integrity of living cells below. Over time, aging and certain disease processes can alter skin pigmentation and its ability to protect itself from environmental damage.
Within the integumentary system, the hypodermis and deep fascia play crucial roles in skin structure and function. The hypodermis, with its fat stores, has a significant impact on the appearance and texture of the skin. As one ages or experiences certain health conditions, these structures can change leading to hypopigmentation or hyperpigmentation and altering the protective functions of the skin.