Which of the following is NOT a function of skin?

The function that is not primarily associated with the skin is blood circulation. While the skin plays a role in regulating blood circulation through its blood vessels and can influence blood flow to the skin surface for various physiological responses, the primary functions of the skin itself include protection, sensation, and temperature regulation.

Protection refers to the skin's role as a barrier against environmental factors such as pathogens, chemicals, and physical abrasions. Sensation involves the skin's ability to detect stimuli through specialized nerve endings, contributing to our sense of touch and perception of pain, temperature, and pressure. Temperature regulation is achieved through mechanisms such as sweating and adjusting blood flow to the skin, which helps maintain a stable internal body temperature.

Therefore, while blood circulation is a crucial physiological process, it is not a direct function of the skin itself in the same manner as the other listed functions.