Merocrine glands in dogs are located in their paw pads. These glands are part of the dog's cooling system, activated when the dog is hot. Unlike humans, who sweat across much of their skin, dogs primarily release sweat through these paw pads to help regulate their body temperature. The function of the merocrine glands is to produce sweat that evaporates from the surface of the paw pads, providing a cooling effect that helps to reduce the dog's overall body temperature during hot conditions or vigorous exercise.