PATHOLOGY

Detailed explanation-1: -Skin color is mainly determined by a pigment called melanin. Melanin is produced by melanocytes through a process called melanogenesis. The difference in skin color between lightly and darkly pigmented individuals is due to their level of melanocyte activity; it is not due to the number of melanocytes in their skin.

Detailed explanation-2: -Melanin is predominantly restricted to the basal layer (or Stratum basale) of the human epidermis, where it is found in both melanocytes (MCs), the cells that make melanin, and in nearby keratinocytes (KCs), the cells of the epidermis that accept melanin.

Detailed explanation-3: -Cells called melanocytes located in the skin, produce melanin. Melanin gives the skin its color. In certain conditions melanocytes can become abnormal and cause an excessive amount of darkening in the color of the skin. Hyperpigmented concentric rings over the tibia are secondary to prior inflammation.