The sebaceous glands belong to the group of the exocrine glands. They produce sebum (Latin sebum), which not only moisturizes and nourishes the skin, but also protects it against external factors. The work of the sebaceous glands is mainly regulated by hormones. Read about the functions and structure of sebaceous glands and find out what their diseases are.

Contents:

  1. Functions of the sebaceous glands
  2. Activity of the sebaceous glands
  3. Diseases of the sebaceous glands
    • Seborrhea
    • Acne
    • Seborrheic dandruff
    • Newborn seborrheic eczema
    • Tumors of the sebaceous glands

The sebaceous glandsare located all over the body. The exception is the thick skin of the hands and feet. Most of these glands do not open directly onto the skin's surface, but into the hair follicle. Each hair combined with its extension muscle (this is the muscle whose contraction causes "goosebumps") and the adjacent sebaceous gland to form the so-called sebaceous-hair unit.

Parallel muscle contraction also pushes the sebum out of the gland. There is another very important structure near the opening of the sebaceous gland to the hair follicle. It is the stem cell niche, or "storehouse" of cells capable of dividing. These cells play an important role in the renewal of the epidermis and its products.

The number of sebaceous glands in the skin is more or less constant throughout life and ranges from 100 to 800 / cm² depending on its location. Most of them are found on the scalp, face and upper torso. On the other hand, it is believed that the size of the sebaceous glands increases with age, and this process is most rapid during adolescence.

The sebaceous glands are bubble-shaped, similar to miniature bunches of grapes. They are made of modified epithelial cells that are able to accumulate drops of fat and other components of sebum. For this reason, the cells of these glands when viewed under a microscope have a characteristic, "foamy" appearance.

The sebaceous glands are characterized by a unique way of producing secretions. We call it holocrine secretion(from Greek holos - whole). In this type of secretion, whole cells and their contents die, and at the same time become components of the produced secretion. In order for sebum to be constantly produced, it is necessary to systematically renew the cells of the sebaceous gland through their continuous division. The entire process of creating a new cell, accumulating sebum components, until it dies and is excreted on the outer surface of the skin, takes about a week.

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Functions of the sebaceous glands

The most important function of the sebaceous glands is, of course, the production of sebum, also known as sebum. This secretion is made up of various types of fats such as triglycerides, phospholipids, and cholesterol derivatives. Additionally, sebum contains remnants of the cells from which it is formed, as well as substances with antimicrobial activity. A thin layer of sebum on the skin provides it with adequate hydration, preventing excessive water loss.

It is worth knowing that a similar role is played by a special type of sebaceous gland located in the eyelids - the so-called meibomian glands. The tallow they produce produces a thin, greasy film on the surface of the tear film. As a result, the tears cannot easily evaporate from the surface of the conjunctiva. This way the eye is protected from drying out.

In addition to protection against excessive evaporation, sebum is a layer impermeable to water from the outside. This property makes our skin waterproof. From a chemical point of view, the secretion of the sebaceous glands is slightly acidic. It is one of the factors that help protect against microorganisms. Sebum also has a nourishing function, providing the skin with valuable antioxidants - such as fat-soluble vitamin E.

The sebaceous glands have the ability to produce and transform fats and their derivatives. The lipids produced by them can have both anti-inflammatory and pro-inflammatory effects. Due to these properties, some diseases of the sebaceous glands arise precisely on the basis of local inflammation.

The sebaceous glands develop during the fetal life, usually around the 15th week of life. Even then, they fulfill an important function, producing components of the fetal fluid. It is a special discharge that covers the skin of the fetus and newborn baby. During vaginal delivery, the liquor provides adequate glide, facilitating the passage through the birth canal. The fetal gunk probably has an additional numberother roles: maintains proper skin hydration and prevents it from cooling down, and also constitutes a barrier against external infectious agents.

Activity of the sebaceous glands

The most important factor regulating the size and activity of the sebaceous glands is the concentration of certain groups of hormones. The role of the most important stimulants is assigned to androgens, which include, among others testosterone. The gonads and adrenal glands are the main places for the production of androgens, although the sebaceous glands also have the ability to produce them locally within the skin. The function of inhibiting the production of sebum is performed, among others, by estrogens. In addition to sex hormones, other adrenal hormones (such as cortisol) and hormones produced by the pituitary gland (growth hormone, prolactin) have an effect on the sebaceous glands.

The moment of development of the sebaceous glands in the fetus is related to the stimulation with androgens from the mother and those produced by the placenta. After birth, the secretory activity of the glands declines and remains at a very low level until the onset of puberty. Changes in the hormonal balance and increased production of androgens intensely stimulate the activity of the sebaceous glands. Excessive production of sebum, characteristic of, among others, seborrhea and acne lesions, may be one of the symptoms of endocrine disorders.

Diseases of the sebaceous glands

Most diseases of the sebaceous glands are associated with their excessive stimulation. Uncontrolled secretory activity may have only minor cosmetic effects or lead to more serious inflammation and purulent changes. In addition to the overproduction of sebum, neoplastic processes may also be the cause of diseases of the sebaceous glands, although these are relatively rare cases. The most important diseases of the sebaceous glands include:

Seborrhea

Increased production of sebum, also known as seborrhea, is most commonly seen on the scalp, face and upper torso. Seborrhea causes oily skin and the second blockage of the sebaceous glands. Chronic seborrhea can cause diseases of the smooth (acne) and hairy skin (seborrheic dandruff). At the root of seborrhea are hormonal changes, such as in adolescence, but also genetic factors and deficiencies of certain vitamins. The direct influence on the development of seborrhea is attributed to skin yeast infections.

Acne

Common acne is one of the most common skin diseases - it is estimated that up to 80% of people experience this problem at least once in their life. Acne develops oncaused by many factors: increased seborrhea, hormonal changes, infection with anaerobic bacteria of the speciesPropionibacterium acnes , as well as local inflammation.

Acne with a slight intensity is dominated by blackhead-type lesions associated with overproduction of sebum and excessive keratinization of the epidermis around the hair follicles. In more advanced forms, skin lesions are accompanied by the development of inflammation, bacterial superinfection, and the formation of pus-filled pustules and cysts.

The most common form of acne is juvenile acne, associated with overstimulation with androgens in adolescence. Other disease subtypes include:

  • baby acne (occurring temporarily in the first months of a child's life)
  • drug acne (caused most often by hormonal drugs)
  • cosmetic acne (associated with blockage of the sebaceous glands by cosmetics applied to the face)

We treat acne, depending on its severity, locally or generally. In therapy, preparations from several groups are used simultaneously: anti-seborrhea, antibacterial, anti-inflammatory and exfoliating.

Seborrheic dandruff

Seborrheic dandruff is a condition of the scalp, arising from seborrhea. If the scalp is very greasy, it is called oily dandruff. Skin lesions usually include superficial exfoliation, although in very severe cases scabs and inflammatory infiltrates may form. The treatment usually involves anti-dandruff shampoos.

Newborn seborrheic eczema

Increased activity of the sebaceous glands in newborns is related to stimulation by androgens coming from the outside. Their source is both the mother's organism and placental production. Seborrheic eczema on the scalp is called cradle cap. The skin lesions are not painful, and they are usually not itchy. After several weeks, when androgen levels in the blood of the newborn decrease, seborrheic eczema disappears by itself.

Tumors of the sebaceous glands

Within the sebaceous glands, benign and malignant neoplasms may develop. An example of a benign neoplasm is sebaceous adenomas, usually in the form of multiple nodules on the face. These types of changes are not dangerous and can be surgically removed. In rare cases, benign neoplasms of the sebaceous glands may accompany genetic syndromes associated with an inherited predisposition to the development of malignant neoplasms of internal organs.

An example of such a disease is the Muir-Torre syndrome, in which, in addition to adenomassebaceous diseases there is an increased risk of developing cancer of the gastrointestinal tract and reproductive organs.

The most dangerous cancer that develops in the sebaceous glands is the so-called sebaceous cancer. It is a rare but very aggressive cancer. The most common place of its development are the sebaceous glands in the eyelids. The mainstay of treatment is complete surgical excision of the lesion, as this neoplasm is not susceptible to radiotherapy.

About the authorKrzysztof 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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Category:

Dermatology