Apocrine: Glands, Function and Disorders
Apocrine refers to a specific type of secretion and a class of sweat glands found mainly in the armpits and groin area of the human body.
Things worth knowing about "Apocrine"
Apocrine refers to a specific type of secretion and a class of sweat glands found mainly in the armpits and groin area of the human body.
What Does Apocrine Mean?
Apocrine is a medical term describing a specific mode of secretion in which a gland cell releases part of its own cytoplasm along with the secreted substance. The word originates from the Greek words apo (away from) and krinein (to separate). In human biology and dermatology, the term is most commonly used in relation to apocrine sweat glands.
Apocrine Mode of Secretion
Biology distinguishes three fundamental types of glandular secretion:
- Merocrine (eccrine): Secretion is released via exocytosis without loss of cellular material. This is the most common type.
- Apocrine: A portion of the apical cytoplasm (the part of the cell facing the gland lumen) buds off and is released together with the secretion.
- Holocrine: The entire cell disintegrates to become the secretion, as seen in sebaceous glands.
Apocrine Sweat Glands
Apocrine sweat glands are specialized skin glands that differ from the common eccrine sweat glands. They are larger, situated deeper in the dermis, and typically open into hair follicles rather than directly onto the skin surface.
Distribution in the Body
Apocrine glands are predominantly found in the following locations:
- Axillae (armpits)
- Inguinal and genital regions
- Anal region
- Areola of the mammary gland
- External auditory canal (here called ceruminous glands)
Function and Secretion
Apocrine glands produce a viscous, milky secretion rich in proteins, lipids, and steroid compounds. Unlike eccrine glands, apocrine glands play little role in thermoregulation in humans. Their secretion is initially odorless, but when broken down by bacteria on the skin surface, it is converted into odor-active compounds, resulting in characteristic body odor (bromhidrosis).
Hormonal Activation
Apocrine glands become functionally active only at puberty, stimulated by sex hormones (androgens). They remain inactive in children. Their secretion is triggered by emotional stress, pain, and sexual arousal and is controlled via the autonomic nervous system (adrenergic stimulation).
Apocrine Glands and Disease
Disorders of the apocrine glands can cause or contribute to various medical conditions:
- Hidradenitis suppurativa (acne inversa): A chronic inflammatory disease of apocrine glands and hair follicles, characterized by painful nodules, abscesses, and scarring.
- Bromhidrosis: Unpleasant body odor caused by bacterial breakdown of apocrine secretions.
- Fox-Fordyce disease: Blockage of apocrine ducts causing intense itching, mainly in the armpits.
- Apocrine carcinoma: A rare malignant tumor arising from apocrine glands.
Apocrine Glands in Diagnostics
In dermatology and pathology, distinguishing apocrine from eccrine glandular structures is clinically important. Histological examination of tissue samples reveals characteristic features of apocrine cells, such as the so-called decapitation secretion, in which apical cytoplasmic blebs protrude into the gland lumen. These features assist in the diagnosis of skin tumors and diseases of the adnexa (accessory skin structures).
References
- Fritsch, P. - Dermatologie und Venerologie. Springer Verlag, 3rd edition (2018).
- Mescher, A.L. - Junqueira's Basic Histology: Text and Atlas. McGraw-Hill Education, 16th edition (2021).
- World Health Organization (WHO) - International Classification of Diseases (ICD-11). Available at: https://icd.who.int
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