Diseases of the sebaceous glands: symptoms and treatment. Sebaceous gland - location, function and role The cells of the sebaceous gland are called

Sebaceous glands (glandulae sebaceae) - alveolar glands. They are located in the dermis throughout the skin, especially on the face, scalp, interscapular region and sternum. Glands are absent on the palms and soles. Most of the excretory ducts of the sebaceous glands open into the hair follicle, and the excretory ducts of the glands located on the inner layer of the foreskin, labia minora, clitoris, wings of the nose, at the border of the extreme border of the lips, open directly on the surface of the skin. Each hair is surrounded by 6-8 sebaceous glands.
The sebaceous glands originate from the ectodermal germ layer. The main layer of the sebaceous glands consists of cells similar to the basal cells of the epidermis. They constantly multiply, so the composition of the cells is regularly updated. As a result of fatty degeneration of the cells themselves, a secretion of the sebaceous glands is formed, released through the excretory duct into the funnel of the follicle. The main function of sebum is to lubricate the surface of the skin and hair, it gives them softness and protects the hair from brittleness and the skin from dryness.

Sebaceous glands are located almost throughout the skin with the exception of the skin of the palms and soles and are overwhelmingly associated with hair follicles. They can vary significantly in size, location and structure in different areas of the skin. It is most saturated with large S. liquids. skin of the scalp, cheeks and chin (400-900 glands per 1 cm2). Sebaceous glands located in areas of the skin devoid of hair (lips, corner of the mouth, glans penis, inner layer of the foreskin, clitoris, labia minora, nipples and areola of the mammary glands) are called free or separate.

Structure, dimensions and location of the S. zh. in the skin depend on the timing of hair formation. S. zh. are located in the reticular (reticular) layer of the dermis, lying in a somewhat oblique direction between the hair follicle and the pilus levator muscle. When it contracts, the hair straightens, which, by exerting pressure on the hair, promotes increased secretion.

Formed simple S. consists of an excretory duct, lined from the inside with multilayered squamous non-keratinizing epithelium, to the terminal secretory part - a sac, surrounded on the outside by a thin connective tissue capsule. Along the periphery of the sac (under the capsule) there is a continuous layer of undifferentiated cells lying on the basement membrane and having high mitotic activity - the so-called germ layer. Closer to the center of the sac are larger secretory cells containing small fat vacuoles. The closer the cells are located to the center, the more pronounced are the signs of death of the nucleus and the entire cell, the larger and more abundant are the fat vacuoles, which can merge into conglomerates. In the center of the sac there is cellular detritus, consisting of decayed secretory cells, which is the secretion of the gland.

Blood supply of the s. provide blood vessels that nourish the hair root system. S. zh. innervated by cholinergic and adrenergic nerve fibers. The endings of cholinergic nerve fibers reach the basement membrane, located on its surface, while the endings of adrenergic nerve fibers pierce the basement membrane, penetrate the parenchyma and surround secretory cells.
Throughout S.'s life. undergoing significant restructuring. By the time of birth, they are quite developed and function intensively. During the first year of life, the growth of the glands predominates against the background of reduced secretion; later, their partial atrophy occurs, especially in the skin of the legs and back. The period of puberty is characterized by increased growth of S. and increasing their function. In older people, involution of the blood vessels is observed, manifested by a simplification of their structure, a decrease in size, proliferation of connective tissue, and a decrease in the metabolic and functional activity of secretory cells. Part S. zh. May disappear completely with age
The sebaceous glands secrete about 20 g of sebum per day, which in most glands is brought to the surface of the skin through the root sheath of the hair, and in free glands - directly from the excretory duct. Secret S. gives elasticity to the hair, softens the epidermis (in the fetus it protects the skin from maceration), regulates the evaporation of water and the excretion of certain water-soluble metabolic products from the body, prevents the penetration of certain substances from the environment into the skin, and has an antimicrobial and antifungal effect.
Regulation of the function of the stomach. carried out by the neurohumoral route, mainly by sex hormones, which can cause a physiological increase in the activity of S. (hyperplasia, secretion of a large amount of secretion). Thus, in newborns they are influenced by progesterone and pituitary hormones of the mother circulating in the blood, in adolescents during puberty - activation of the gonadotropic function of the anterior pituitary gland, adrenal cortex, and increased activity of the gonads.
Pathology includes malformations, functional disorders, dystrophic changes, inflammatory processes, as well as tumors of the stomach. To malformations of S. zh. include congenital asteatosis (lack of sebaceous secretion or its sharp decrease as a result of insufficient development of the gland), as well as heterotopia of the gland. into the mucous membrane of the mouth and the red border of the lips (Fordyce disease). The appearance of S. in the oral cavity with Fordyce's disease is not accompanied by subjective sensations; they are detected by chance during examination in the form of small translucent pale yellow nodules on the oral mucosa. No treatment is required.
Functional disturbances in the activity of the stomach. are caused by damage to the autonomic central or peripheral nervous system, disruption of hormonal regulation, metabolism, etc. Increased activity of the nervous system. noted in patients with epidemic viral encephalitis as a result of damage to the autonomic centers, with catatonic stupor (substupor), with lesions of the anterior pituitary gland, adrenal cortex, gonads associated with increased function, for example, with Itsenko-Cushing's disease, seminoma, etc. Decreased function of these endocrine glands, as a result of their damage, leads to a decrease in the functional activity of the glands, which is noted, for example, during orchiectomy.
A common pathological condition, which is based on a violation of the secretory function of the stomach. with a change in the chemical composition of the sebaceous secretion, seborrhea occurs. In this case, changes in the skin often lead to the formation of excretory ducts. sebaceous plugs (comedones), as well as atheromas (steatoma) - retention cysts of the stomach. Multiple cysts of the stomach, resulting from nevoid dysplasia of the epidermis, can be observed in pilosebocystomatosis.
Dystrophic changes in S. may be age-related (in old age) or develop as a result of a number of acquired diseases - scleroderma, skin atrophy, etc. Dystrophic changes in the skin are often common. are associated with hereditary characteristics of their morphology and functional activity, in particular with the thinning of the epithelium lining the excretory ducts of the stomach and the secretory epithelium of the sacs, a decrease in secretory function and the formation of superficial epidermal cysts - milia, for example in dystrophic forms of epidermolysis bullosa.
Inflammatory processes in the stomach. are often observed, especially during puberty against the background of seborrhea. They are characterized by the formation of acne, in which the inflammatory process can develop both in the walls of the stomach. and the surrounding tissue (pustular acne), and spread into the deep layers of the skin (indurative acne) around the skin. and hair follicles, often involving subcutaneous tissue (phlegmous acne).
Benign tumor of the stomach. is a true adenoma of the sebaceous gland; observed rarely in adults and elderly people in the form of a dense round, often single nodule on the face or back, it is an encapsulated organoid tumor of a lobular structure.
To malignant tumors of the stomach. include basalioma (see Skin, tumors), which has locally destructive growth. Cancer S. g. - a rare type of epithelial malignant tumor, most often developing from the glands of the cartilage of the eyelids - the meibomian glands.

Function of the sebaceous glands.

The sebaceous glands, being part of the pilosebaceous complex, belong to the holocrine glands. They produce sebum, which contains wax and cholesterol esters, squalene and triglycerides. Sebum is secreted through the excretory duct into the hair follicle and then covers the skin, apparently performing a protective function. In addition, it has antifungal properties. Sebaceous glands are present on the entire surface of the body, with the exception of the palms and soles.

Sebaceous glands are skin glands whose secretion is a fatty lubricant for the surface of the skin and hair.

They are located almost all over the skin, with the exception of the soles of the feet and the skin of the palms. They vary significantly in size, and also have different structures and localization in different areas of the skin. Most accumulation of sebaceous glands is observed in the scalp, as well as on the chin and cheeks. They are also located in areas devoid of hair: in the corners of the mouth, on the lips, clitoris, nipples, labia minora, glans penis, foreskin.

The location, size and structure of the sebaceous glands depend on the period of hair formation. They are located in the reticular (reticular) layer of the dermis and lie in a slightly oblique direction between the hair lifter muscle and its follicle. When the hair muscle contracts, it straightens and exerts pressure, promoting the secretion of the sebaceous gland.

A simple sebaceous gland consists of an excretory duct and a terminal secretory part. The excretory duct is a non-keratinized squamous epithelium lined from the inside, and the terminal secretory part is a sac, externally surrounded by a thin connecting capsule. Under the capsule there is a germ layer - undifferentiated cells with high mitotic activity, which lie on the basement membrane. In the center of the terminal secretory part there is cellular detritus, consisting of decayed secretory cells - the secretion of the gland.

Blood vessels provide blood supply to the glands and nourish the hair root system. The sebaceous glands are supplied by adrenergic and cholinergic nerve fibers. Adrenergic nerve fibers pierce the basement membrane and surround the secretory cells, and cholinergic nerve fibers are located on the surface of the basement membrane.

Throughout a person's life, the sebaceous glands change. At the time of birth, they are very developed and function intensively. During the first year of life, against the background of reduced secretion of the sebaceous glands, their growth predominates; later they partially atrophy, especially in the skin of the back and legs.

During puberty, their growth intensifies again, and the function of the sebaceous glands increases.

In old age, the glands stop developing, which is manifested in a decrease in their size, a simplified structure, and a decrease in the functional and metabolic activity of secretory cells. Some glands disappear altogether with age.

Normally, iron secretes approximately 20 g of sebum per day. The secretion of the sebaceous glands makes hair elastic, regulates water evaporation, softens the epidermis, prevents the penetration of certain substances from the outside into the skin, and has an antifungal and antimicrobial effect.

The function of the sebaceous glands is regulated neurohumorally, mainly by sex hormones, which can sometimes cause an increase in their activity (secretion of too much secretion, hyperplasia). In newborn children, the glands are strongly influenced by pituitary maternal hormones and progesterone, and during puberty they are affected by activation of the gonadotropic function of the anterior part of the pituitary gland, increased activity of the gonads, and activation of the adrenal cortex.

Pathologies of the sebaceous glands

The pathology of the glands consists of malformations, dystrophic changes, functional disorders, inflammation of the sebaceous glands and tumors of the glands.

Dysfunction of the sebaceous glands, as a rule, occurs as a result of damage to the autonomic peripheral or central nervous system, metabolic disorders and hormonal regulation. Often, increased activity of the glands can be observed with catatonic stupor, lesions of the anterior lobe of the pituitary gland, gonads, adrenal cortex, as well as with epidemic viral encephalitis due to damage to the autonomic centers. A decrease in the function of the glands leads to a decrease in the function of the endocrine glands, for example, during orchiectomy.

Often, as a result of malfunction, blockage of the sebaceous glands occurs. One of the most common pathologies, which is based on a violation of secretory function, is seborrhea. With this disease, sebaceous-horn plugs, or comedones, appear in the ducts of the glands, resulting from blockage of the sebaceous glands. Also a common occurrence is the occurrence of atheromas - retention cysts. Multiple cysts also occur in pilosebocystomatosis due to disruption of nevoid dysplasia of the epidermis.

Dystrophic changes can be either age-related or develop due to some acquired diseases (scleroderma, skin atrophy, etc.). Often dystrophic changes are caused by hereditary factors.

Inflammation of the sebaceous glands occurs quite often, especially during puberty. Inflammation is characterized by the formation of acne. In this case, the inflammatory process can involve the walls of the glands and the tissue around them (pustular acne), and can spread into the deeper layers of the skin, sometimes even involving the subcutaneous tissue (phlegmous acne).

Benign tumors of the sebaceous glands include true adenoma of the gland, which most often develops in adults and elderly people and looks like a dense round nodule on the back or face.

Malignant tumors include basalioma, which has locally destructive growth. Most often, sebaceous gland cancer develops from the glands of the cartilage of the eyelids - the meibomian glands.

Sebaceous glands(glandulae sebaseae) - skin glands, the secretion of which serves as a fatty lubricant for the hair and skin surface.

Sebaceous glands located in areas of the skin devoid of hair (lips, corner of the mouth, glans penis, inner layer of the foreskin, clitoris, labia minora, nipples and areola of the mammary glands) are called free or separate.

The structure, size and location of the sebaceous glands in the skin depend on the timing of hair formation. The sebaceous glands are located in the reticular (reticular) layer of the dermis, lying in a somewhat oblique direction between the hair follicle and the hair lifter muscle.
When it contracts, the hair straightens, which, by putting pressure on the sebaceous glands, promotes increased secretion.

The formed simple sebaceous gland consists of an excretory duct, lined from the inside with stratified squamous non-keratinizing epithelium, to the terminal secretory part - a sac, surrounded on the outside by a thin connective tissue capsule. Along the periphery of the sac (under the capsule) there is a continuous layer of undifferentiated cells lying on the basement membrane and having high mitotic activity - the so-called germ layer.

Closer to the center of the sac are larger secretory cells containing small fat vacuoles. The closer the cells are located to the center, the more pronounced are the signs of death of the nucleus and the entire cell, the larger and more abundant are the fat vacuoles, which can merge into conglomerates. In the center of the sac there is cellular detritus, consisting of decayed secretory cells, which is the secretion of the gland.

The blood supply to the sebaceous glands is provided by blood vessels that nourish the hair root system. The sebaceous gland is innervated by cholinergic and adrenergic nerve fibers. The endings of cholinergic nerve fibers reach the basement membrane, located on its surface, while the endings of adrenergic nerve fibers pierce the basement membrane, penetrate the parenchyma and surround secretory cells.

Throughout life, the sebaceous glands undergo significant restructuring. By the time of birth, they are quite developed and function intensively. During the first year of life, the growth of the glands predominates against the background of reduced secretion; later, their partial atrophy occurs, especially in the skin of the legs and back. The period of puberty is characterized by increased growth of the sebaceous glands and an increase in their function. In older people, involution of the sebaceous glands is observed, manifested by a simplification of their structure, a decrease in size, proliferation of connective tissue and a decrease in the metabolic and functional activity of secretory cells. Some sebaceous glands may disappear completely with age,

The sebaceous glands secrete about 20 g of sebum per day, which in most glands is brought to the surface of the skin through the root sheath of the hair, and in free glands - directly from the excretory duct. The secretion of the sebaceous glands gives elasticity to the hair, softens the epidermis (in the fetus it protects the skin from maceration), regulates the evaporation of water and the excretion of certain water-soluble metabolic products from the body, prevents the penetration of certain substances from the environment into the skin, and has an antimicrobial and antifungal effect.

Regulation of the function of the sebaceous glands is carried out neurohumorally, mainly by sex hormones, which can cause a physiological increase in the activity of the sebaceous glands (hyperplasia, secretion of large amounts of secretion). Thus, in newborns they are influenced by progesterone and pituitary hormones of the mother circulating in the blood, in adolescents during puberty - activation of the gonadotropic function of the anterior pituitary gland, adrenal cortex, and increased activity of the gonads.

Pathology includes developmental defects, functional disorders, dystrophic changes, inflammatory processes, as well as tumors of the sebaceous glands. Malformations of the sebaceous glands include congenital asteatosis (lack of sebum secretion or its sharp decrease as a result of insufficient development of the sebaceous glands), as well as heterotopia of the sebaceous glands. into the mucous membrane of the mouth and the red border of the lips (Fordyce disease). The appearance of sebaceous glands in the oral cavity with Fordyce's disease is not accompanied by subjective sensations; they are discovered by chance during examination in the form of small translucent pale yellow nodules on the oral mucosa. No treatment is required.

Functional disturbances in the activity of the sebaceous glands are caused by damage to the autonomic central or peripheral nervous system, disruption of hormonal regulation, metabolism, etc. Increased activity of the sebaceous glands was noted in patients with epidemic viral encephalitis as a result of damage to the autonomic centers, with catatonic stupor (substupor), with lesions of the anterior lobe pituitary gland, adrenal cortex, gonads associated with increased function, for example, in Itsenko-Cushing's disease, seminoma, etc. A decrease in the function of these endocrine glands as a result of their damage leads to a decrease in the functional activity of the sebaceous glands, which is noted, for example, during orchiectomy .

A common pathological condition, which is based on a violation of the secretory function of the sebaceous glands with a change in the chemical composition of the sebaceous secretion, is seborrhea. At the same time, changes in the skin often lead to the formation of sebaceous-horn plugs (comedones) in the excretory ducts of the sebaceous glands, as well as atheromas (steatoma) - retention cysts of the sebaceous glands. Multiple sebaceous cysts resulting from nevoid dysplasia of the epidermis can be observed in pilosebocystomatosis.

Dystrophic changes in the sebaceous glands can be age-related (in old age) or develop in a number of acquired diseases - scleroderma, skin atrophy, etc. Dystrophic changes in the sebaceous glands are often associated with hereditary characteristics of their morphology and functional activity, in particular with the thinning of the epithelium lining the excretory ducts sebaceous glands, and the secretory epithelium of the sacs, a decrease in secretory function and the formation of superficial epidermal cysts - milia, for example in dystrophic forms of epidermolysis bullosa.

Inflammatory processes in the sebaceous glands are often observed, especially during puberty against the background of seborrhea. Characterized by the formation of acne, in which the inflammatory process can develop both in the walls of the sebaceous glands and surrounding tissue (pustular acne), and spread into the deep layers of the skin (indurative acne) around the sebaceous glands and hair follicles, often involving the subcutaneous tissue (phlegmous acne ).

A benign tumor of the sebaceous glands is a true adenoma of the sebaceous gland; observed rarely in adults and elderly people in the form of a dense round, often single nodule on the face or back, it is an encapsulated organoid tumor of a lobular structure.

Malignant tumors of the sebaceous glands include basalioma, which has locally destructive growth. Sebaceous gland cancer is a rare type of epithelial malignant tumor, most often developing from the glands of the cartilage of the eyelids - the meibomian glands.

To understand the formation of acne (blackheads), you need to know the normal structure and location of the pilosebaceous follicles.

Sebaceous pilosebaceous follicle

The pilosebaceous follicle (pilosebaceous bulb, hair follicle) consists of 3 elements:

hair,
hair follicle (bulb),
sebaceous gland.

All hair follicles have a sebaceous gland, which releases its secretion into the funnel of the hair follicle. However, there are also free sebaceous glands, not associated with hair follicles:

meibomian glands of the eyelids,
glands of the preputial sac (the cavity of the foreskin),
glands around the nipple,
sebaceous glands along the edges of the lips and genital mucosa.

The structure of the sebaceous gland

The sebaceous gland is a simple branched gland and consists of 2 parts: end section And excretory duct. The sebaceous glands have the so-called holocrine type of secretion, i.e. During secretion, these cells are completely destroyed and all their contents turn into secretion.

In different areas of the skin, sebaceous glands differ in size and number. The largest of them are located on the face and scalp; they also have the most active secretion. The sebaceous glands are unevenly distributed in the skin. In order decrease in the number of sebaceous glands in the skin can be distinguished:

face, scalp (400-900 sebaceous glands per 1 square cm),
ears, upper half of the body, back between the shoulder blades,
other parts of the body (10-20 times less than on the face).

The terminal section of the sebaceous gland consists of lobules formed by special cells - sebocytes(from lat. sebaceous - sebaceous). Each lobule contains several hundred concentrically (in circles around a common center) sebocytes. There is no lumen in the lobules, and the secretion produced ( sebum) enters the excretory duct, which flows into the hair canal.

On the periphery of the sebaceous gland there are immature, frequently dividing cells (they have no lipids and large nuclei). With the help of hemidesmosomes they are attached to their support - basement membrane. As they move away from the basal membrane, the cells mature: they increase in size, the volume of the nuclei decreases, and fats accumulate inside. Mature cells in the center of the sebaceous gland lose contact with each other and are gradually destroyed. From the destroyed cells, a secretion of the sebaceous gland is formed, which is called sebum. Sebum and sebocyte residues accumulate in the excretory duct of the sebaceous gland and in the hair canal.

Hair canal(follicular canal) has 2 parts:

short top - acroinfundibular(between the confluence of the excretory duct of the sebaceous gland and the funnel of the hair follicle, from the Latin infundibulum - funnel),
long bottom - infrainfundibular(below the confluence of the excretory duct of the sebaceous gland).

The excretory duct of the sebaceous gland opens into the upper part of the hair canal and is lined stratified squamous keratinizing epithelium(like the epidermis).

According to the size of the sebaceous glands, pilosebaceous follicles are divided into 3 types:

pilosebaceous follicles of terminal hair with small sebaceous glands(eyebrows, edges of eyelids, beard area);
sebaceous follicles with average sebaceous glands and short excretory ducts (most common);
sebaceous follicles with large sebaceous glands, wide excretory ducts and wide openings of the follicle.

The openings of hair follicles are called at times. The pores have a diameter of up to 2.5 mm and are visible to the naked eye. Type 3 follicles are found on the face (up to 800 per square cm) and upper torso. Acne affects only type 3 follicles. Acne patients have many more of these follicles than usual.

Functions of the sebaceous glands

The secretion of the sebaceous glands (sebum) is secreted onto the surface of the skin and performs the following functions:

hair lubricant,
softening the skin (giving softness, elasticity),
protection against drying out,
UV protection,
Thanks to its bactericidal and fungicidal action, it protects against fungal and pustular infections. Sapienic acids in the composition of sebum they have direct bactericidal activity.

At normal body temperature, sebum reduces the surface tension of sweat, which allows sweat to be evenly distributed on the skin without the formation of individual droplets.

In addition, the sebaceous glands are independent endocrine organ, responding to changes in the level of androgens - (especially testosterone) and some others. Sebocytes are also capable of synthesizing vitamin D 3.

Sebaceous glands are formed at 13-15 weeks of embryonic development. After birth they are inactive. Activity increases during puberty. After 40 years, age-related changes and aging of the sebaceous glands become noticeable.

Instructions

The sebaceous glands are located on the human skin between the hair follicles and the muscles that lift the hair. According to the structure, the glands can be classified as alveolar type, since they consist of a sac and an excretory duct.

The production of sebum begins when the muscle that lifts the hair is working. Moving along the surface of the hair, the secretion appears on the surface of the skin. Such glands have excretory ducts that open into the hair follicles. There are places on the human body where sebaceous glands are absent. These parts include the feet and palms.

There are also glands that have excretory ducts that open directly onto the surface of the skin, since the excretory flow is connected to the upper layer of the epidermis. They are concentrated in large numbers on those parts of the body where there is no hair. During the day they secrete about 20 g of sebum.

The number and activity of the sebaceous glands changes throughout a person’s life. This is directly related to the problem of teenage acne, pimples and other skin diseases. During this period, intensive work of the sebaceous glands, accompanied by increased secretion, leads to clogging of the pores with sebum. On the face, the sebaceous glands are most dense.

The functions of the sebaceous glands are primarily related to the sebum produced. The rate of sebum formation is influenced by a number of different factors, but mainly it depends on the functioning of the endocrine system and the person’s age. In addition to physiological characteristics, the activity of the sebaceous glands is associated with lifestyle. For example, under severe emotional stress, the amount of secretion can greatly increase compared to its normal production.

Sebum, which consists of a mixture of lipids, helps strengthen the barrier and antimicrobial properties of the skin. In addition, it gives the skin elasticity and protects it from drying out. Sebum contains a number of acids, which neutralize them when alkalis come into contact with the skin. In the event of temperature changes in the air, the sebaceous glands are directly involved in maintaining a constant body temperature due to physical changes in the composition of the water-lipid mantle. Metabolic products, as well as medicinal and toxic substances, are removed from the body by the sebaceous glands due to their abundant blood supply.