Eccrine Sweat Glands

1. Overview

Eccrine sweat glands are simple, coiled tubular glands that play a primary role in regulating body temperature through the secretion of sweat. They are the most numerous type of sweat gland in the human body and are essential for thermoregulation, waste excretion, and skin hydration. Unlike apocrine glands, eccrine glands function independently of hair follicles and are active from early infancy.

2. Location

Eccrine glands are widely distributed throughout the body but are most concentrated in specific areas:

• Palms of the hands

• Soles of the feet

• Forehead and scalp

• Axillae and trunk

They are found in the dermis and open directly onto the surface of the skin via sweat pores, unlike apocrine glands which empty into hair follicles.

3. Structure

Eccrine sweat glands have a simple anatomical structure consisting of two major parts:

• Secretory portion:

  • Located deep in the dermis or upper hypodermis.

  • Formed by a coiled tubular structure lined with clear cells, dark cells, and myoepithelial cells.

  • Clear cells secrete the watery component; dark cells secrete glycoproteins.

  • Myoepithelial cells contract to expel sweat into the duct.

• Duct portion:

  • Extends through the dermis and epidermis.

  • Reabsorbs sodium and chloride ions, making the final sweat hypotonic.

  • Opens directly onto the skin surface via a pore.

4. Function

Eccrine glands serve several vital functions:

• Thermoregulation: Through evaporative cooling, eccrine sweat reduces body temperature in response to heat or physical exertion.

• Excretion: Eliminates small amounts of metabolic waste products such as urea, lactic acid, and salts.

• Hydration of skin: Maintains the hydration and plasticity of the stratum corneum, contributing to the skin barrier function.

• pH maintenance: Sweat helps maintain the skin’s slightly acidic pH (acid mantle), which inhibits microbial growth.

5. Physiological role(s)

Eccrine sweat glands play essential roles in maintaining internal homeostasis and skin health:

• Body temperature regulation: As part of the autonomic nervous system response, they are activated by sympathetic cholinergic fibers during heat exposure or stress.

• Electrolyte balance: By controlling salt reabsorption in the duct, eccrine glands help regulate sodium loss during sweating.

• Emotional sweating: Activated not just by heat but also emotional stress, especially in palms and soles.

• Protection against microbes: Sweat contains antimicrobial peptides such as dermcidin, aiding in innate immunity.

6. Clinical Significance

Dysfunction or abnormal activity of eccrine sweat glands can result in several clinical conditions:

• Hyperhidrosis:

  • Excessive sweating, often localized (e.g., palms, soles, axillae) or generalized.

  • May be primary (idiopathic) or secondary to conditions like hyperthyroidism or anxiety.

  • Treatment includes antiperspirants, botulinum toxin injections, oral anticholinergics, or sympathectomy.

• Anhidrosis/Hypohidrosis:

  • Absent or reduced sweating, impairing thermoregulation and increasing the risk of heat stroke.

  • May result from genetic conditions (e.g., ectodermal dysplasia), nerve damage, or skin diseases.

• Miliaria (heat rash):

  • Blockage of eccrine ducts leads to sweat retention and inflammatory lesions, especially in hot, humid environments.

• Cholinergic urticaria:

  • Allergic reaction to one's own sweat, triggered by heat or exercise, resulting in hives and itching.

• Cystic fibrosis diagnosis:

  • Sweat chloride testing is used to diagnose cystic fibrosis due to defective chloride reabsorption in eccrine ducts.