1.1.4.3 Sweat glands
According to different structures and functions，human sweat glands are usually divided into small glands and apocrine sweat glands.
Small glands，also known as eccrine sweat glands，are single-curved tubular glands composed of secretory parts and ducts.The secretory part is located in the deep part of the dermis and the subcutaneous tissue.It is composed of a single layer of cells，arranged in a tube and coiled into a spherical shape.The ducts are composed of two layers of small cubic cells with relatively smaller diameter，pass through the dermis，and directly opens to the sweat pores.Except for lips，eardrum，nail bed，nipple，medial foreskin，glans，labia minora，and clitoris，the small glands are all over the body，with relatively more in the palms，soles，armpits and forehead，and fewer in the back.The main function of the small glands is to regulate body temperature.The small glands in the palms and soles of the feet also have the effect of improving tactile sensitivity and increasing adhesion.The small glands are dominated by the sympathetic nervous system，and the neurotransmitter is acetylcholine.(https://www.daowen.com)
The apocrine sweat glands，also known as the large glands，are large tubular glands composed of a secretory part and a duct.They are mainly distributed in the armpits，areola，periumbilical，and perineum，occasionally found in the face，scalp，and trunk.In addition，ceruminous glands of the external auditory canal and eyelid ciliary glands are also apocrine sweat glands.The secretory part is located in the subcutaneous fat layer.The gland is a layer of flat，cubic，or columnar secretory cells with myoepithelial cells and basement membrane zone.The structure of the duct is similar to that of the small glands，but its diameter is about 10 times that of the small glands.It opens above the opening of the sebaceous glands in the upper part of the hair follicles and occasionally directly on the skin surface.The secretion of apocrine sweat glands is mainly affected by sex hormones，so the secretion is strong in adolescence.The apocrine sweat glands are also dominated by the sympathetic nervous system，and the neurotransmitter is norepinephrine.