Sweat glands are structures formed in the human skin, adapted to the production and secretion of sweat. Their most important task is to regulate our body temperature. Contrary to appearances, sweat secretion is a rather complicated process, controlled by both nervous and hormonal signaling. On average, human skin has from 1.5 million to 5 million sweat glands. Find out how the sweat glands are built, what is the production of sweat, and in which conditions the functioning of the sweat glands can be altered.
Sweat glands(Latinglandulae sudoriferae ) take part in the thermoregulation process through the secretion of sweat. In humans, we are dealing with eccrine sweat glands and apocrine sweat glands.
Structure and types of sweat glands
The structure of the sweat glands is not too complicated. They consist of two main structures: secretion coils and sweat ducts.
The secretory part is located in the deep layers of the dermis (the so-called reticulate layer), while the drainage lines lead through the successive layers of the skin, finally exiting the epidermis.
The secretory part consists of two types of cells: light and dark. Each of them is responsible for the secretion of other ingredients into the sweat. Clear cells produce large amounts of watery discharge, while regulating its electrolyte composition (i.e. sodium, potassium, calcium and chloride content).
In turn, dark cells are responsible for the secretion of the so-called glycoproteins, or proteins related to the sugar chain. Both the secretory parts and the drainage ducts of the sweat glands are lined with a special type of cell - the so-called myoepithelial cells (to be exact, muscle-epithelial cells). Their most important function is contractility, thanks to which sweat can be squeezed out of the ducts leading to the outer surface of the skin.
There are two types of sweat glands, differing in location, functioning and composition of the secretion produced. These include eccrine and apocrine (also known as odorous) glands.
- eccrine sweat glands
The eccrine glands are theremost frequently located around the hands and feet. It is worth mentioning that these are the only skin products in these locations - but we will not find hair or sebaceous glands there. In addition to the hands and feet, eccrine glands are found almost everywhere - on the scalp, trunk and limbs. We won't find them only in the skin of the lips and genitals.
Most people who talk about sweat glands mean the eccrine subtype - it is responsible for the production of watery sweat, thus enabling the regulation of body temperature.
- apocrine sweat glands
Apocrine glands are also called scent glands. It is their secretion that is responsible for the unpleasant smell of sweat that arises when it comes into contact with the bacteria that inhabit the surface of our skin. The apocrine glands do not go directly outside the epidermis, but into the hair follicles. For this reason, they are found only in the hairy skin. The greatest concentration of this type of gland is in the armpits, around the groin and perineum. Their discharge is relatively thick and oily.
The apocrine glands are not stimulated by an increase in body temperature, but remain dependent on emotional stimuli (for example, fear). Their functioning begins only in the period of sexual maturation under the influence of changes in the levels of sex hormones. Apocrine glands play an important role in animals, influencing, among other things, their sexual behavior.
Sweat production. Sweat gland functions
About 99% of sweat is water. The remaining 1% is for ions (mainly sodium and chloride), as well as small amounts of metabolic products such as urea, ammonia and uric acid.
Sweat production must be strictly controlled by the body - unrestricted activity of the sweat glands could result in excessive loss of water and valuable electrolytes. Under normal circumstances, our sweat glands produce approximately 500-750 ml of sweat per day. However, during intense exercise such as a marathon, sweat secretion can be as high as 2-3 liters per hour.
The work of the sweat glands is primarily controlled by the autonomic nervous system. Its activity is independent of our will - we are not able to stimulate or inhibit sweating at our own request.
The most important role of the sweat glands is to regulate the body's temperature. The increase in our body temperature stimulates the brain's thermoregulation center, which activates the sweat glands through the fibers of the nervous system.
Evaporation of sweat fromThe skin's surface requires the release of certain amounts of heat, so that the body temperature is lowered. Thermoregulation is "de alt with" mainly by the eccrine glands.
The apocrine sweat glands are innervated adrenergically. This means that their most important stimulant is the stress hormone adrenaline. For this reason, the activity of the apocrine glands is greatest in emotional stress situations - fear, pain or high stress.
Apart from nervous regulation, the hormonal balance has a significant influence on the work of the sweat glands. The most important hormone is aldosterone produced in the adrenal glands. The main task of aldosterone is to regulate the water and electrolyte balance. Thanks to it, it is possible to reabsorb sodium ions from the originally produced sweat. In this way, the body prevents excessive loss of this element.
Some scientific studies indicate that sweat glands may be involved in the regeneration of the epidermis and wound healing. Probably the most important role here is played by the precursor cells of these glands, although the exact mechanisms of their participation in repair processes have not been known yet.
Sweat glands - dysfunction
Diseases related to sweat glands can arise on various grounds. Their cause can be both the improper work of the glands themselves and a disturbance in the regulation of the nervous system or the endocrine system. Inflammatory and neoplastic processes can take place within the sweat glands. It is also worth remembering that disturbances in the amount and composition of sweat can be a symptom of many systemic diseases. The most important diseases affecting the sweat glands are:
- excessive sweating (hyperhidrosis)
Hyperhidrosis is a state of excessive sweating - sweat production then exceeds the amount required to maintain a normal body temperature. Excessive sweating can affect your entire body as well as specific locations (for example, the hands themselves).
We distinguish primary hyperhidrosis, the cause of which has not been known so far, and secondary hyperhidrosis - arising from other diseases. Excessive sweating can be a symptom of hormonal, neurological and cancer disorders. Examples of diseases associated with hyperhidrosis are: hyperthyroidism, diabetes mellitus (especially in situations of hypoglycaemia, i.e. a sudden drop in blood glucose) and Parkinson's disease.
Hyperhidrosis may also be one of the symptoms of neoplasms of the lymphatic system - lymphomas. In this case, drenching night sweats typically occur. Another causes of hyperhydrosis aredisturbance of the functioning of the autonomic nervous system that controls sweat secretion. Damage to the autonomic nerve fibers from trauma (such as a spinal cord injury) or neuropathy may manifest as increased sweating.
In the treatment of hyperhydrosis, antiperspirants, drugs inhibiting the activity of the autonomic nervous system as well as powders and dusts that dry the skin are used. In local hyperhidrosis, local injection of botulinum toxin (botox) brings good results.
Surgical procedures are reserved for the most advanced cases: removal or destruction of sweat glands, as well as cutting nerve fibers innervating specific groups of these glands. However, before we start treating hyperhidrosis symptomatically, we should carefully check if it is not a sign of another systemic disease.
Treatments to reduce excessive sweating
- decreased sweating (hypohydrosis, anhydrosis)
Reduced sweating, or hypohydrosis, occurs much less frequently than hyperhidrosis. However, it is much more dangerous - the lack of sweat production makes it impossible to lower the body temperature in overheating situations. The complete lack of sweating is called anhidrosis. The cause of decreased sweating is usually generalized skin diseases that change its structure. One of the examples of such diseases is hypohydrotic ectodermal dysplasia, which is a congenital disorder of the development of the skin and its appendages. Improperly developed sweat glands are not able to act as thermoregulators, which in extreme cases may even be life threatening.
- prickly
Potówki is a problem that mainly affects infants and young children, although sometimes it also occurs in adults. These are tiny, itchy, or burning blisters that appear in overheated areas. Their source is the local overproduction of sweat combined with its difficult outflow. Removal of the cause - local overheating - usually causes skin lesions to disappear.
- multiple abscesses of armpits
Multiple abscesses of the armpits, also known as inverted acne, is an inflammatory disease of the apocrine sweat glands. It is caused by a bacterial infection, most often caused by staphylococci. Purulent lesions appear only in places where there are apocrine glands - in the armpits and (less often) in the perineum. Treatment consists of local antibiotics and surgical incision of abscesses.
- cystic fibrosis
Cystic fibrosis is an example of a disease in which the composition of sweat is disturbed. Due to the inborn mutation of the channels in the cell membrane of the sweat gland epithelium, chloride ions are not reabsorbed and the sweat becomes very s alty. Increased chloride excretion is the basis of the sweat test, which is a very simple and useful tool for the diagnosis of cystic fibrosis.
- sweat gland tumors
Both benign and malignant neoplasms can develop from sweat gland cells. Sweat gland cancers are usually more aggressive compared to more common skin malignancies, such as, for example, squamous cell carcinoma. Tumors of the sweat glands are very rare. For this reason, their treatment is a big challenge, as there is a lack of studies on large groups of patients that would allow to compare the effectiveness of different methods of therapy.
About the author
Krzysztof BialaziteA medical student at Collegium Medicum in Krakow, slowly entering the world of constant challenges of the doctor's work. She is particularly interested in gynecology and obstetrics, paediatrics and lifestyle medicine. A lover of foreign languages, travel and mountain hiking.
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