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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
There are two types of sweat glands in man, the eccrine and apocrine glands. The eccrine sweat glands are distributed over the entire body surface except for a few specific regions. They are numerous in the palms and soles. These glands develop independently of hair follicles and are situated in the deep dermis. They traverse the epidermis via a duct to open directly onto the surface of the skin. These glands are simple coiled tubular structures with four major components: the terminal secretory portion, the coiled duct, the straight duct, and the intraepidermal duct. Three types of cells have been described in the eccrine sweat gland secretory coil region. At the periphery of the secretory portion are the myoepithelial cells, which sit on the basement membrane. Clear cells have been observed with lipid inclusions. Intracellular canaliculi pass in between adjacent clear cells. These cells are responsible for producing the aqueous sweat. The last cell type is the dark cell which produces mucin. On the luminal surface of the dark cell, microvilli are located.229–232 Eccrine sweat glands are innervated by postganglionic sympathetic nerve fibers. Blood vessels surround the secretory portion and coil around the ducts of the sweat glands. Eccrine sweat glands are found only in a few mammals with hair. When present, they are usually restricted to the digital pads or the snout.230
Temperature Regulation
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Responses to high temperatures are aimed at decreasing heat gain and increasing heat loss. Decreased heat gain is achieved by behavioural changes (reduced activity, reduced feeding and reduced heat gain from the environment using appropriate clothing and housing). Sweating is the main method of increasing heat loss as the environmental temperature increases. There are about two million sweat glands in the body, but these are not evenly distributed. About 50% of the sweat production occurs in the chest and back, and women have lower rates of sweat production compared with men. Although the maximum rate of producing sweat is 3 L/h, this cannot be sustained, and the maximum amount of sweat produced is 12 L/day. The proximal region of the sweat gland produces a hypotonic solution that is modified by solute reabsorption as the fluid moves along the duct towards the skin surface. At low rates of secretion, the sodium content of sweat is low (5 mmol/L), but at high secretion rates, it can reach 10 times the basal value because there is less time for ductal reabsorption. Evaporation of sweat is important for heat loss; the latent heat of evaporation of water at 37°C is 2.4 kJ/mL, and the majority of this heat comes from the body.
Peripheral Autonomic Neuropathies
Published in David Robertson, Italo Biaggioni, Disorders of the Autonomic Nervous System, 2019
In essential hyperhidrosis, the constituents of sweat and sweat gland morphology are normal. The aetiology of essential hyperhidrosis is unknown and pharmacological blockage of sweat gland activity has been an unsatisfactory treatment for this condition. Sympathectomy cures the socially embarrassing sweating that usually starts in childhood, but does not become burdensome until adult life. If not treated surgically, hyperhidrosis lasts throughout life, and it is most troublesome when it affects the hands, feet and axillae. Recently, abnormal vasomotor function has also been noted in some of these patients, and baroreflex activity becomes normal after surgical extirpation of the relevant sympathetic ganglia. Results of biofeedback therapy for essential hyperhidrosis are conflicting and, in cases in which it has been successful, the permanence of reduction in sweating has not been established.
Anti-ageing peptides and proteins for topical applications: a review
Published in Pharmaceutical Development and Technology, 2022
Mengyang Liu, Shuo Chen, Zhiwen Zhang, Hongyu Li, Guiju Sun, Naibo Yin, Jingyuan Wen
Glands are partial appendages, and the sebaceous glands are the small oil-producing glands directly open to the skin's surface and attach to hair follicles. These glands are most abundant on the scalp and face. They secrete an antibacterial substance known as sebum, a mixture of free fatty acids, glycerides, and cholesterol (Wertz 2018). Sebum acts as a lubricant and is the source of SC plasticizing lipids. The essential function of sebum is to maintain the pH of the skin’s surface (Ma et al. 2019). Sweat glands are present in the lower layers of the dermis and are responsible for temperature regulation. Distributed all over the body, except around the areola, secretions from sweat glands are a diluted salt solution with a pH of around 5 (Ma et al. 2019). Conversely, the apocrine glands are only located in areas such as the armpit and perianal, and they are usually larger than other counterparts (Farah et al. 2020). These appendages also change during puberty, affecting the permeation of the skin (Hirt et al. 2019).
Proposed mechanism of action of tap water iontophoresis for treatment of hyperhidrosis
Published in Cogent Medicine, 2018
The secretory portion of the gland includes dark cells and clear cells, along with myoepithelial cells. Dark cells secrete sialomucin, an acidic glycoproteins that is a precursor of mucin (Constantine & Mowry, 1966; Munger, 1961), which, when combined with water, produces mucus. However, the specific function of the dark cells remains somewhat enigmatic, relative to the well-known secretory function of the clear cells (Bovell, 2015), though it appears that a key facet of sweat production is the release of mucopolysaccharide into the lumen of the gland by dark cells via secretory vacuoles (Munger, 1961). Examination of sweat glands following activation (both those from individuals experiencing hyperhidrosis and those experiencing normal sweat levels) revealed considerable cellular debris in the lumen of the duct, including lipid droplets (Bovell, Clunes, Elder, Milsom, & Jenkinson, 2001). At the same time, dark cells had been degranulated, indicating release of lipid-containing vacuoles. Individuals with anhidrosis and hypohidrosis have eccrine glands with degranulated and shrunken dark cells (Sano et al., 2017), highlighting the importance of dark cell function, and particularly mucin secretion, for normal sweat function. While mucin secretion by dark cells appears to be an integral component of sweat production, the bulk of the sweat production is attributable to the clear cells that secrete water-containing solutes into the lumen (Munger, 1961). Indeed, recent work concludes that clear cells are responsible for the excess secretions characteristic of hyperhidrosis (Bovell et al., 2011).
Investigation on aetiological factors in patients with hyperhidrosis
Published in Cutaneous and Ocular Toxicology, 2018
As distinct from primary form, secondary HH develops as a result of an underlying medical condition. Excessive sweating results from several causes such as drug use, infections, endocrine and metabolic disorders, toxins, genetic diseases, malignancies, spinal cord injuries, cardiovascular or respiratory disorders, anxiety or stress, inflammatory skin diseases, or structural defects associated with abnormal sweat glands2,3,30. Half of our patients were in secondary HH group. Like some other investigators, we found pathologies such as hypoglycaemia and hyperglycaemia, thyroid disease, and cardiovascular disease as aetiological factors in this group of patients30–33.