What are Apocrine Glands?
Apocrine glands are a type of
gland that belongs to the larger family of
exocrine glands. They are primarily found in specific areas of the body such as the axilla (armpits), the areola of the nipple, and the anogenital region. These glands are associated with hair follicles and are responsible for producing a thick, milky secretion that becomes mixed with bacteria on the skin's surface, leading to body odor.
Histological Structure
The histological structure of apocrine glands is quite distinct. These glands are coiled, tubular structures located in the dermis and subcutis. The secretory portion of the gland comprises a single layer of
epithelial cells that surround a lumen. The cells have a large, round nucleus and abundant eosinophilic cytoplasm, which is due to the presence of numerous secretory granules. The ducts of apocrine glands are lined by a double layer of cells and open directly into hair follicles.
Mechanism of Secretion
Apocrine glands employ a unique mechanism of secretion known as
apocrine secretion. In this process, the apical portion of the secretory cells pinches off, releasing cytoplasm along with the secretory product into the gland lumen. This is different from other types of exocrine glands, such as
merocrine glands, which release their products via exocytosis without losing any part of the cell.
Function and Role in the Body
While the exact physiological role of apocrine glands is not entirely understood, they are believed to play a role in human pheromone production. The secretion from these glands is initially odorless but becomes odorous when acted upon by skin bacteria. This suggests a role in social and sexual communication. Additionally, apocrine glands are thought to have a role in thermoregulation and lubrication of the skin. Clinical Significance
Several clinical conditions are associated with apocrine glands. One common condition is
hidradenitis suppurativa, a chronic inflammatory disorder that affects apocrine gland-bearing areas of the body. In this condition, blockages and infections of the glands lead to painful nodules and abscesses. Another condition is
apocrine gland carcinoma, a rare form of cancer that arises from the apocrine glands. Understanding the histology of these glands is crucial for diagnosing and managing such conditions.
Comparison with Other Gland Types
Apocrine glands differ from other types of glands, such as
eccrine glands and
sebaceous glands. Eccrine glands are widely distributed across the skin and are involved in thermoregulation through the secretion of a watery sweat that evaporates to cool the body. Sebaceous glands, on the other hand, secrete sebum, an oily substance that lubricates the skin and hair. Both eccrine and sebaceous glands employ different secretion mechanisms compared to apocrine glands.
