Neural Control of Sweat Secretion: A Review

Y. Hu, C. Converse; M.C. Lyons; W.H. Hsu

Disclosures

The British Journal of Dermatology. 2018;178(6):1246-1256. 

In This Article

Abstract and Introduction

Abstract

Background: Humans have 4 million exocrine sweat glands, which can be classified into two types: eccrine and apocrine glands. Sweat secretion, a constitutive feature, is directly involved in thermoregulation and metabolism, and is regulated by both the central nervous system (CNS) and autonomic nervous system (ANS).

Objectives: To explore how sweat secretion is controlled by both the CNS and the ANS and the mechanisms behind the neural control of sweat secretion.

Methods: We conducted a literature search on PubMed for reports in English from 1 January 1950 to 31 December 2016.

Results and Conclusions: Acetylcholine acts as a potent stimulator for sweat secretion, which is released by sympathetic nerves. β–adrenoceptors are found in adipocytes as well as apocrine glands, and these receptors may mediate lipid secretion from apocrine glands for sweat secretion. The activation of β–adrenoceptors could increase sweat secretion through opening of Ca2+ channels to elevate intracellular Ca2+ concentration. Ca2+ and cyclic adenosine monophosphate play a part in the secretion of lipids and proteins from apocrine glands for sweat secretion. The translocation of aquaporin 5 plays an important role in sweat secretion from eccrine glands. Dysfunction of the ANS, especially the sympathetic nervous system, may cause sweating disorders, such as hypohidrosis and hyperhidrosis.

Introduction

Humans have a powerful capability to maintain body temperature, release waste products and respond to emotional stresses by sweating. Nearly 4 million exocrine sweat glands are widely distributed in the integument throughout the entire human body.[1] The sweat glands begin to develop during the third month of fetal development as a cord of epithelial cells, and resemble adult sweat glands in the eighth month.

There are two principal sweat gland types in humans: eccrine and apocrine (Figure 1[2]). Eccrine glands comprise 90% of the total number of sweat glands,[1] which cover the entire body and are involved in thermoregulation.[3] Apocrine sweat glands are located mainly in the axillae, the mons pubis, the external auditory meatus, the areolae and the circumanal area.[4] The apocrine to eccrine sweat gland ratio in the axillary region is 1 : 1 and 1 : 10 in the rest of the body.[2]

Figure 1.

Basic structure of sweat glands. The eccrine sweat gland is made of tubular epithelia comprising the secretory coil and a reabsorptive sweat duct (RSD). The RSD comprises a straight segment (traversing the dermal layer) and the intraepidermal sweat duct, which opens directly onto the skin surface. Apocrine glands are located in the subcutaneous fat deep in the dermal layer, and are composed of a glomerulus of secretory tubules that funnel toward an excretory duct that opens into the hair follicle.2 Apocrine sweat glands do not usually open directly onto the surface of the skin as eccrine sweat glands do. Instead, these glands open and secrete sweat into the hair follicles' piliary canals.

This review explores how sweat secretion is controlled by both central nervous system (CNS) and autonomic nervous system (ANS) and mechanisms behind the neural control of sweat secretion.

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