Apocrine secretion describes a unique method by which certain glands in the human body release their products. This process involves the shedding of a portion of the secretory cell’s cytoplasm and membrane along with the substance being released. This distinguishes it from other forms of glandular secretion where cells remain largely intact, making it a distinct type of bodily fluid.
The Apocrine Glands and Their Secretion Process
Apocrine glands are primarily found in specific areas of the human body, including the armpits (axillae), the area around the nipples (areolae), and the anogenital region. These glands are typically associated with hair follicles, with their ducts opening into the pilary canal rather than directly onto the skin surface. This anatomical arrangement means the secreted product travels along the hair shaft to reach the skin.
The cellular mechanism of apocrine secretion involves a part of the cell budding off. Secretory cells accumulate material at their apical ends, forming small protrusions. These membrane-bound portions, containing both the secretory product and some cytoplasm, then pinch off from the main cell body and are released into the gland’s lumen. While this process involves some loss of cellular material, the cell remains largely functional.
What Apocrine Secretion Does
Apocrine secretion is characterized by its viscous, oily composition, which includes fatty acids, proteins, and steroids. This secretion is initially odorless when released from the gland. However, its interaction with bacteria naturally present on the skin’s surface leads to the breakdown of these components. This bacterial decomposition generates the strong smell commonly associated with body odor.
The primary biological function of apocrine secretion in humans is not fully understood, but its role in producing body odor through bacterial interaction is clear. Beyond odor, there is ongoing research into its potential roles in human communication, such as pheromonal communication or contributing to an individual’s unique scent signature.
Apocrine Secretion Compared to Other Glands
Apocrine secretion differs from other types of glandular secretions, especially from eccrine sweat glands. Eccrine glands are found over most of the body, and their ducts open directly onto the skin surface. Their primary function is thermoregulation, producing a thin, watery sweat that helps cool the body through evaporation. This eccrine sweat is largely composed of water and salts.
In contrast, apocrine glands are concentrated in specific areas like the armpits and groin, and they release their product into hair follicles. The secretion from apocrine glands is thicker, more viscous, and contains lipids, proteins, and steroids. Apocrine glands become active only after puberty due to hormonal changes, whereas eccrine glands are functional from birth. The mechanism of secretion also differs, with apocrine glands releasing cellular material, while eccrine glands secrete their product via exocytosis without losing cell parts.