What is the primary function of eccrine (merocrine) sweat glands?

The primary function of eccrine (merocrine) sweat glands is thermal regulation. These glands are distributed widely across the body, particularly on the palms, soles of the feet, and forehead. Their main role is to secrete a watery sweat directly onto the skin's surface, which helps to cool the body through the process of evaporation. When the body temperature rises due to exercise or environmental heat, eccrine sweat glands activated, allowing sweat to evaporate and thus lowering the body's temperature.

In contrast, other options relate to functions that are not the primary purpose of eccrine sweat glands. While protection against pathogens can be attributed to other mechanisms in the skin, such as the acid mantle and other immune functions, eccrine glands primarily focus on thermoregulation. Water absorption is not a function of these glands, as they do not absorb water but rather secrete it to the outside of the body. The production of sebum is carried out by sebaceous glands, not eccrine sweat glands, which specifically are responsible for sweat secretion.