SEBACEOUS GLANDS

From Big Medical Encyclopedia

SEBACEOUS GLANDS (glandulae sebaceae) — glands of skin, the secret to-rykh serves as fatty lubricant for hair and the surface of skin.

Page. are available only in leather of mammals. At birds, amphibians and other animals of gland of skin only remind Page., without being essentially those. Being essentially similar on gistol. to a structure, Page. can have essential distinctions in sizes, localization and complexity of a structure not only at different types of animals, but also in different sites of skin of a separate individual.

Embryology

Concerning terms of formation of Page. opinions are contradictory. So, by data I. I. Podvysotskoy (1971), their education occurs both in the early post-natal period, and in the period of puberty. According to other data, laying of the Village. at the person occurs for 3 — 6 months of embryonic development in an upper third of an outside root vagina of a hair in the form of kolboobrazny accumulation of the epithelial cells growing into a surrounding derma. From a venter of this accumulation of cells the secretory department, from the tyazh connecting to an outside root vagina — an output channel, from surrounding connecting fabric — the capsule of Page forms. The simple gland formed thus, expanding, turns in branched, and sometimes and difficult, lobular.

Topography

Page. are located practically on all skin except for skin of palms and soles and are in the majority connected with follicles of hair (a sebaceous gland of a hair — gl. sebaceae pili). It is most sated with large Pages. skin of a pilar part of the head, cheeks and a chin (400 — 900 glands on 1 cm2). Page., the bays located in the sites of skin deprived of hair (a corner of a mouth, a balanus, an internal leaf of a prepuce, a clitoris, small vulvar lips, nipples and peripapillary circles of mammary glands), received the name free, or separate, Page. (gll. sebaceae separatae).

Anatomy, histology and age changes

Structure, size and arrangement of Page. in skin depend on terms of a bookmark hair (see). Page. are located in a mesh (reticular) layer of a derma, lying in a little slanting direction between a follicle of a hair (folliculus pili) and a muscle-podnimatelem of a hair (m. arrector pili). At its reduction there is a straightening of a hair, to-ry, putting pressure upon Page., promotes the strengthened allocation of a secret (see. Piloerektion ).

Mikropreparat of skin with located in it a sebaceous gland and a follicle of a hair: 1 — a follicle of a hair; 2 — an output channel of a sebaceous gland; 3 — the sack of a sebaceous gland filled with a secret from the broken-up secretory cells; 4 — a rostkovy layer of cells of a sebaceous gland; 5 — a muscle-podnimatel of a hair; coloring hematoxylin-eosine; x 80.

Created simple by Page. (fig.) consists of an output channel (ductus gl. sebaceae) covered from within multilayer flat not - a keratosic epithelium, and a trailer secretory part — a sack (sacculus gl. sebaceae), surrounded outside with the thin connective tissue capsule. On the periphery of a sack (under the capsule) the continuous layer of the undifferentiated cells lying on a basal membrane and having high mitotic activity, a so-called rostkovy layer of cells of Page is located. These cells are rich with RNA and have an underdeveloped cytoplasmic reticulum and Golgi's complex. Closer to the center of a sack larger secretory cells with the developed Golgi's complex and not granular cytoplasmic reticulum containing separate small fatty vacuoles are located. The closer cells are disposed to the center, especially signs of death of a kernel and all cell are expressed in them, the fatty vacuoles are larger and more plentiful, to-rye can merge in conglomerates. In the center of a sack there is a cellular detritis consisting of the broken-up secretory cells to-ry and is a secret of gland.

Blood supply of Page. provide the blood vessels feeding root system of a hair (see Hair).

Page. are innervated by cholinergic and adrenergic nerve fibrils. The terminations of cholinergic nerve fibrils reach a basal membrane, being located on its surface whereas the terminations of adrenergic nerve fibrils probodat a basal membrane, get into a parenchyma and surround secretory cells. There are also specific and topographical differences in character of a cholinergic innervation of Page.

Throughout life of Page. are exposed to considerable reorganization. By the time of the birth they are rather developed and function intensively. Within the first year of life growth of glands against the background of reduced secretion prevails, further there is their partial atrophy, especially in skin of shins and spins. Strengthening of growth and increase in function of Page is characteristic of the period of puberty. At elderly people involution of Page is observed., shown in simplification of their structure, reduction of the sizes, growth of connecting fabric and decrease in metabolic and functional activity of secretory cells. Part of the Village. with age can disappear completely. Degree of an atrophy of Page. in different areas of a body it is various, napr, in skin of a pilar part of the head it is less expressed, than in other areas.

Physiology

Page. per day allocate apprx. 20 g of skin fat, a cut at the majority of glands it is brought to the surface of skin through a root vagina of a hair, and at free glands — directly from an output channel. Allocation of a secret happens on holocrine type (see. Glands ). Secret of Page. gives elasticity to a hair, softens epidermis (at a fruit protects skin from maceration), regulates evaporation of water and removal from an organism of nek-ry water-soluble products of exchange, interferes with penetration into skin of nek-ry substances from the environment, renders antimicrobic and anti-fungal effect.

Regulation of function of Page. it is carried out in the neurohumoral way, generally sex hormones (see), to-rye can cause fiziol. strengthening of activity of Page. (a hyperplasia, allocation of a large number of a secret), napr, at newborns — influence circulating in blood of progesterone and hypophyseal hormones of mother, at teenagers during puberty as a result of activation of gonadotropic function of a front share of a hypophysis, bark of adrenal glands, increase in activity of gonads.

Pathology

Pathology of Page. includes malformations, functional disturbances, dystrophic changes, inflammatory processes, and also tumors.

To malformations of Page. carry an inborn asteatosis (lack of sebaceous secretion or its falloff as a result of underdevelopment of Page.), and also heterotopy of Page. in a mucous membrane of a mouth and a red border of lips — Fordyce's disease. Emergence of Page. in an oral cavity at this disease is not followed by subjective feelings, they are found accidentally at survey in the form of small translucent small knots of pale yellow color on a mucous membrane of a mouth. Treatment at Fordyce's disease is not required.

Functional disturbances activity of Page. are caused by defeat of a vegetative, central or peripheral nervous system, disturbance of gorkhmonalny regulation, an obkhmen of substances, etc. Strengthening of activity of Page. it is noted at patients with epidemic viral encephalitis as a result of defeat of the vegetative centers, at the mental diseases which are followed by symptoms of a vagotonia (psychoses, etc.), at defeats of a front share of a hypophysis, bark of adrenal glands, the gonads tied with strengthening of their function, napr at Itsenko's disease — Cushing (see. Itsenko — Cushing a disease ), to a seminoma (see), etc. Depression of function of the specified hemadens as a result of their defeat leads to reduction of functional activity of Page., what is noted, e.g., at an orkhiektomiya (see. Castration , Postkastratsionny syndrome ).

Extended patol. a state, to-rogo disturbance of secretory function of Page is the cornerstone. with change of chemical composition of a grease secret, is seborrhea (see). At the same time seborrheal changes of skin quite often lead to formation in output channels of Page. grease and horn traffic jams — comedones, and also atheromas (oleocysts) — deep retentsionny cysts of Page. (see. Epidermoid cyst ). Multiple cysts of Page., resulting from a nevoid dysplasia of epidermis, can be observed at to a pilosebotsistomatoza (see).

Dystrophic changes Page. can be observed as age changes (at senile age) or at a number of acquired diseases — sclerodermas (see), atrophies of skin (see), etc. However quite often dystrophic changes of Page. are connected with hereditary features of their hmorfologiya and functional activity, in particular, thinning of the epithelium covering output channels of Page., and a secretory epithelium of sacks, decrease in secretory function and formation of superficial epidermal cysts — milium (see), napr, at dystrophic forms of a violent epidermolysis (see. Epidermolysis violent ).

Inflammatory processes in the Village. are observed often, especially during puberty against the background of seborrhea. Are characterized by education eels (see), at to-rykh inflammatory process can develop as in walls of Page. and the fabric (pustular eels) surrounding it and to extend in deep layers of skin (indurative eels) around Page. and follicles of hair, it is frequent with capture of hypodermic cellulose (phlegmonous eels).

Benign tumor Page. — adenoma of a sebaceous gland true — is observed seldom at adult and elderly people in the form of dense roundish, is more often than a single small knot on a face or a back, is the encapsulated organoid tumor of a lobular structure. Incorrectly call adenomas like Pringl, Allopo — Leredda — Darya (see. Adenoma of sebaceous glands ) and Balzera — Menetriye (see. Epithelioma adenoid cystous ) nevus of Page. (cm. Nevus ).

To to malignant tumors Page. carry to bazaliy (see), differing in mestnodestruiruyushchy growth and being intra epidermal cancer. Cancer of Page. — the rare kind of cancer developing from Page., the century, so-called meibomian glands is more often from glands of a cartilage (see. Skin, tumors ).



Bibliography: Kalantayevsky K. A. Gistomorfologiya of sebaceous glands of the person in ontogenesis, Nauch. izv. Kazakhsk. medical in-that, t. 16, page 174, Alma-Ata, 1960; Yu. Seborey's Queens and eels, Minsk, 1972; P about d in y with about c to and I am I. I. Age evolution of sebaceous glands, in book: Theory and practice of dermas. - venerol., under the editorship of E. V. Maystrakha, etc., page 346, L., 1971; V. E. Falcons, Shaba-d and sh S. A. and 3 e l and to and N and T. I. K to a question of an innervation of sebaceous glands, Izv. Academy of Sciences of the USSR, it is gray. biol., No. 6, page 805, 1980, bibliogr.; The sebaceous glands, ed. by W. Montagna, Oxford, 1963.


S. S. Kryazheva; Yu. K. Eletsky (An., gist., embr.).

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