Which feature is characteristic of the apocrine glands?

The characteristic feature of the apocrine glands is that they produce a viscous secretion. These glands are primarily located in areas such as the armpits and groin and are responsible for releasing a thicker, milky fluid that can have a higher lipid content compared to the secretions from other types of sweat glands, like eccrine glands. The secretion often becomes odorous when it interacts with bacteria on the skin surface, contributing to body odor.

The other options pertain to characteristics of different types of glands or functions. For instance, temperature regulation is mainly associated with eccrine glands, which produce a more watery secretion to help cool the body. Apocrine glands do not play a significant role in temperature regulation. Additionally, apocrine glands do not exist in every part of the body; they are specialized and found mainly in specific regions. Lastly, apocrine glands are not limited to the epidermis; they are located deeper in the skin, usually in the dermis layer. Understanding these distinctions helps clarify why the viscous secretion is a defining feature of apocrine glands.