Final answer:
Stains, macules, keratomas, and calluses are skin conditions that arise due to various factors such as pigmentation changes, thickening of epidermis, and repetitive friction. Calluses particularly form to protect skin from repeated pressure or abrasion and can occur on feet and hands. Corns are specialized types of calluses shaped by elliptical motion abrasion.
Step-by-step explanation:
Stains, macules, keratomas, and calluses are all conditions related to the skin. Stains can refer to discolored areas on the skin often caused by pigmentation, while macules are flat, distinct colored areas, like freckles. Keratomas are growths related to thickened areas of the epidermis, often forming calluses which are areas of thickened skin resulting from repetitive friction and pressure. Calluses help to protect sensitive skin underneath by increasing the number of keratinocytes and therefore the thickness of the skin at the point of contact. On the other hand, a corn is a type of callus formed by elliptical-type motion causing abrasion. Conditions like bedsores, which are also known as decubitis ulcers, occur due to prolonged pressure and are considered more serious as they involve necrosis of tissue.
Common sites for callus formation include feet from tightly fitting shoes and hands from repetitive actions such as writing or playing musical instruments. These skin responses are usually harmless and are the body's way of protecting itself, although they may cause discomfort or require treatment if they become excessively thick or irritated.