The structure and role of the basaphil membrane. Structure and functions of the basal lamina (membrane) Basal membrane

basement membrane

Not to be confused with Basal lamina.

The basement membrane (pink) beneath the vascular endothelium and skin epithelium.

basement membrane- a thin acellular layer that separates connective tissue from the epithelium or endothelium. The basement membrane consists of two plates: light (lamina lucida) and dark (lamina densa). Sometimes a formation called a fibroreticular plate (lamina fibroreticularis) is adjacent to the dark plate.

Corneal Fuchs' dystrophy: in the upper part of the corneal section, upon magnification, a basement membrane is visible, usually separating the corneal epithelium from the main substance of the cornea - the stroma. Closer to the center, the ectopic position of the basement membrane is also noticeable - it deviates and passes directly into the thickness of the epithelium above the two cysts. From a review by Klintworth, 2009.

Compound

The basement membrane is formed by the fusion of two plates: the basal lamina and the reticular plate (lamina reticularis). The reticular lamina is connected to the basal lamina by anchoring fibrils (type VII collagen) and microfibrils (fibrillin). Both plates together are called the basement membrane.

The basal lamina may subsequently divide into two layers. The light layer is closer to the epithelium and is called lamina lucida. The dark layer is closer to the connective tissue and is called lamina densa. Lamina densa is electron dense - 30–70 nanometers in width, consists of an underlying network of reticular collagen (type IV) fibrils (a precursor to fibroblasts) that averages 30 nanometers in diameter and 0.1–2 micrometers in thickness.

Notes

Links

Basal membrane - humbio.ru
Basement Membrane Zone (English) - The most important stages in the study of basement membranes, website of the journal Nature.

Wikimedia Foundation. 2010.

Basal implant
Basaglia

See what “Basement membrane” is in other dictionaries:

BASAL MEMBRANE- in vertebrates and humans, a boundary film between the epithelium (or endothelium) and the adjacent loose connective tissue. Serves to strengthen the epithelial cell layer... Big Encyclopedic Dictionary

BASAL MEMBRANE- non-cellular structure in vertebrates and many others. invertebrates at the border of the epithelial layer and the underlying connective tissue. The material of BM in an electron microscope has a fine-grained appearance or is represented by filaments of diameter. 3 5 nm. Contains... ... Biological encyclopedic dictionary

basement membrane- in vertebrates and humans, a boundary film between the epithelium (or endothelium) and the adjacent loose connective tissue. Serves to strengthen the epithelial cell layer. * * * BASAL MEMBRANE BASAL MEMBRANE, in vertebrates... ... encyclopedic Dictionary

basement membrane- (membrana basalis, LNH) 1) a layer of intercellular substance delimiting the epithelium, muscle cells, lemmocytes and endothelium (except for the endothelium of lymphatic capillaries) from the underlying tissue; Possessing selective permeability, B. m. participates in ... ... Large medical dictionary

basement membrane- (Greek basis - basis, lat. membrane - skin, membrane) - a thin membrane in the cochlea of the inner ear, on which the organ of Corti (spiral) is located. Includes various parts of the membrane that are supposed to vibrate in response to... ... Encyclopedic Dictionary of Psychology and Pedagogy

BASAL MEMBRANE- A thin membrane in the cochlea of the inner ear on which the organ of Corti (spiral) is located. Along its length from the base (close to the stirrup) to the apex, it has different thickness, stiffness and mass. Various parts of the membrane vibrate in... ... Explanatory dictionary of psychology

basement membrane- (biol.) in vertebrates and humans, a boundary film between the epithelium (See Epithelium) (or endothelium (See Endothelium)) and the underlying loose connective tissue (See Connective tissue), from which it is formed. B. m. consists of... ... Great Soviet Encyclopedia

BASAL MEMBRANE- in vertebrates and humans, the boundary film between the epithelium (or endothelium) and the adjacent loose connective tissue. cloth. Serves to strengthen the epithelial cell layer... Natural science. encyclopedic Dictionary

Bruch's membrane- Layers of the retina RPE retinal pigment epithelium OS outer segment of photoreceptors IS inner segment of photoreceptors ONL outer nuclear layer OP ... Wikipedia

Membrane- 1. A thin layer of fibrous tissue that serves as the shell of an organ or tissue, the lining of a cavity, a septum, or a fastening structure. See also Basal membrane. The membrane is mucous, the membrane is serous. 2. Surrounding the cell... ... Medical terms

Books

Atlas. The basement membrane of human skin at different age periods. The book contains materials on the ultrastructure of human skin. The epidermis, the dermo-epidermal junction zone and the dermis are considered. Particular attention is paid to the structure and function of the basement membrane...

basement membrane is, basement membrane is waterproofing
basement membrane- a thin acellular layer that separates connective tissue from the epithelium or endothelium. The basement membrane consists of two plates: light (lamina lucida) and dark (lamina densa). Sometimes a formation called a fibroreticular plate (lamina fibroreticularis) is adjacent to the dark plate. Corneal Fuchs dystrophy: in the upper part of the corneal section, upon magnification, a basement membrane is visible, usually separating the corneal epithelium from the main substance of the cornea - the stroma. Closer to the center, the ectopic position of the basement membrane is also noticeable - it deviates and passes directly into the thickness of the epithelium above the two cysts. From a review by Klintworth, 2009.

1 Structure of the basement membrane
2 Functions of the basement membrane
3 Chemical composition of the basement membrane
4 Notes
5 Links

The structure of the basement membrane

Light plate (lamina lucida/lamina rara) - thickness 20-30 nm, light fine-grained layer, adjacent to the plasmalemma of the basal surface of epithelial cells. From the hemidesmosomes of epithelial cells, thin anchor filaments are directed deep into this plate, crossing it. Contains proteins, proteoglycans and pemphigus antigen.
Dark plate (lamina densa) - thickness 50-60 nm, fine-grained or fibrillar layer, located under the light plate, facing the connective tissue. The plate is woven with anchor fibrils that look like loops (formed by type VII collagen), into which collagen fibrils of the underlying connective tissue are threaded. Ingredients: collagen IV, entactin, heparan sulfate.
Reticular (fibroreticular) plate (lamina reticularis) - consists of collagen fibrils of connective tissue associated with anchor fibrils (many authors do not distinguish this plate).

Type of contact between the basement membrane and the epithelium: hemidesmosome - similar in structure to the desmosome, but it is a connection of cells with intercellular structures. Thus, in epithelia, linker glycoproteins (integrins) of desmosomes interact with proteins of the basement membrane. Function - mechanical. Basement membranes are divided into:

two-layer;
three-layer:
intermittent;
solid.

Functions of the basement membrane

Structural;
Filtration (in the renal glomeruli);
Cell migration pathway;
Determines cell polarity;
Affects cellular metabolism;
Plays an important role in tissue regeneration;
Morphogenetic.

Chemical composition of the basement membrane

Type IV collagen contains 1530 amino acids in the form of repeats, interrupted by 19 separating sections. Initially, the protein organizes into antiparallel dimers, which are stabilized by disulfide bonds. Dimers are the main component of anchor fibrils. Provides mechanical strength of the membrane.
Heparan sulfate proteoglycan - is involved in cell adhesion and has antigenic properties.
Entactin has a rod-shaped structure and binds together laminins and type IV collagen in the basement membrane.
Glycoproteins (laminin, fibronectin) - act as an adhesive substrate, with the help of which epithelial cells are attached to the membrane.

Notes

Klintworth GK (2009). "Corneal dystrophies". Orphanet J Rare Dis 4 : 7. DOI:10.1186/1750-1172-4-7. PMID 19236704.
M Paulsson; Basement membrane proteins: structure, assembly, and cellular interactions; Critical Reviews in Biochemistry and Molecular Biology, Vol 27, Issue 1, 93-127, 1992

Links

Basal membrane - humbio.ru
Basement Membrane Zone (English) - The most important stages in the study of basement membranes, website of the journal Nature.
Basement membrane - http://www.pathogenesis.ru

Basal membrane- This is a thin acellular layer that separates the connective tissue of the skin (dermis) from the epithelium. basement membrane is formed through two layers:

light (Latin “lamina lucida”) – the thickness of the layer is up to 30 nm, contains elements such as: proteins, proteoglycans, pemphigus antigen;
dark (Latin “lamina densa”) – the thickness of the layer is up to 60 nm, contains elements such as collagen, entactin, heparan sulfate.

Basal layers are found not only in epithelial tissues, but also in areas where other types of cells are in contact with connective tissue, such as around muscle cells, fat cells, and Schwann cells of nervous tissue.

The firmness and elasticity of the skin largely depends on the quality and integrity of the basement membrane. The membrane is responsible for delivering all the necessary nutrients to the dermis, thereby restoring and rejuvenating the skin. Active processes of intracellular collagen synthesis take place in the basement membrane. It performs mechanical, barrier and metabolic functions for the epidermis and plays an important role in controlling cellular behavior. Through it, the cells of the basal layer of the epidermis are nourished, and consequently, its structure is improved and local immunity is strengthened. Through activation of the membrane, metabolic processes in the dermis are improved, collagen production is stimulated, which is the basis for improving the overall appearance and health of the skin.

basement membrane has the greatest connection with epithelial cells in the area of hemidesmosomes. It is here that “anchor-type” filaments pass from the plasmalemma of epithelial cells from the light layer to the dark one, which, together with bundles of “anchoring” collagen fibrils moving in the opposite direction, ensures a strong connection of the underlying tissue directly with the epithelial one.

Basement membrane - composition of elements

The basement membrane contains the following elements:

Type IV collagen forms the supporting framework of the basement membrane. If type IV collagen is in a healthy state, then the membrane functions correctly, holding both layers of skin together (connective tissue and epidermis).
Type VII collagen - is an anchor-clip that tightly holds and fastens collagen fibrils (bundles) of the basement membrane with collagen fibrils from the dermis, i.e. Type VII collagen “fastens” and holds type IV collagen bundles (the basement membrane that “keeps the epidermis in tone”) and type I and III collagen fibers (the main space of the dermis). As a result, if everything functions and is synthesized on time, we get densely woven skin tissue, which can be described as “young”;
Heparan sulfate proteoglycan is a component involved in cell adhesion processes, demonstrating antigenic properties;
Dimers are a key component of fibrils, providing special membrane strength;
Entactin is a component that binds collagen in the membrane with glycoproteins;
Glycoproteins are an adhesive substrate through which epithelial cells are fixed to the membrane.

Functions of the basement membrane:

The functions of the basement membrane include the following:

Supportive - maintains the shape of organs and blood vessels.
Filtering - forms a selective barrier not only for the movement of molecules, but also cells.
Serves as a specific pathway for cell movement.
Determines cell polarity.
Affects cellular metabolism. Has a regulating effect on skin development.
Plays an important role in tissue regeneration after damage; in case of inferiority of the basement membrane, blisters often form and scar tissue develops.

basement membrane

BASAL MEMBRANE. The junction of the epidermis and dermis occurs in the zone of the basement membrane, which is a compacted amorphous intercellular substance into which the cytoplasmic membranes of basal cells, desmosomes and reticulin (argyrophilic) fibers are embedded.

The basement membrane is the site of fixation of components necessary for immune processes in a number of severe immune-dependent diseases (lupus erythematosus, bullous pemphigoid, Dühring's dermatosis, etc.) and the site of development of subsequent damaging processes.

The basement membrane is of particular importance in the transmission of inducing factors between the dermis and epidermis.

Through the basement membrane, metabolic processes take place between the epidermis, which does not have a blood supply, and the underlying dermis.

Dermis

DERMA consists of connective tissue fibers (collagen, elastic, reticular), cellular elements (histiocytes, fibroblasts, etc.) and an amorphous ground substance.

The dermis is divided into papillary and reticular layers. Upper papillary layer covered with a basement membrane, directly connected to it and the epidermis, has a wavy surface, contains thinner (than the reticular layer) collagen fibers, and many elastic and reticular fibers. The turgor and elasticity of the skin depend on the anatomical and physiological properties of these fibrous structures (especially elastic fibers).

During life, collagen fibers are renewed and re-synthesized. Elastic fibers are not restored, so in old age and with certain diseases their number decreases, function decreases, and the skin becomes sluggish and flabby.

Mesh layer The dermis has coarser collagen fibers that intertwine with each other, are arranged in bundles parallel to the surface of the skin, and determine its tension (Langer's lines). This is the most durable part of the leather. Collagen fibers in the deeper sections form powerful fibrous cords and a large-loop network, woven into the fascia and aponeuroses of the underlying tissues.

Subcutaneous base

The subcutaneous base is formed from a fibrous framework and fat cells. Its thickness is variable. There is no subcutaneous base on the eyelids, under the nail plates, in the area of the foreskin and labia minora, it is insignificant (up to 2 mm) on the nose, ears, and red border of the lips. The subcutaneous base is most pronounced in the area of the buttocks and abdomen (10 cm or more).

The dermis and subcutaneous tissue contain a well-developed network of blood and lymphatic vessels. Large arterial vessels, coming from the underlying fascia and aponeuroses, they form a deep network at the border with the subcutaneous base. Supplying blood to the hypodermis and dermis, they form thin plexuses around the hair follicles, sebaceous and sweat glands (double network). Repeatedly anastomosing with each other, the vessels create a superficial network at the base of the papillary layer, from which capillary loops are formed in each papilla.

Venous vessels They basically repeat the course of the arterial ones, but have three plexuses.

Lymphatic system located in the papillary layer in the form of sinuses; in the deeper layers of the dermis it forms tubules, lacunae and capillaries. In the subcutaneous layer, the lymphatic vessels are large, with valves. Some skin vessels may be in a collapsed state and function only under heavy loads.

Innervation of the skin. Individual centers of the skin analyzer are scattered throughout the cerebral cortex, and the main part is located in the posterior central gyrus. The dermis and subcutaneous base contain sensory cerebrospinal and autonomic nerves. In the dermis proper, the subcutaneous base, some of the nerves end in the form of encapsulated plexuses - tactile (Meissner), lamellar (Vater-Pacini), Ruffini corpuscles, Krause flasks. Nerve fibers without membranes end in the epidermis. Smooth and cross-striated The muscles of the skin are located in the dermis and subcutaneous layer. A bundle of smooth muscle fibers “connects” the hair follicle and the dermal papilla. When they contract, the skin on the surface becomes bumpy (“goose bumps”), and the hair takes on a more vertical position (stands on end).

Smooth muscles not associated with hair follicles are present in the skin of the scalp, on the forehead, cheeks, back of the hands and feet, in the skin of the scrotum, foreskin, around the nipples of the mammary glands, anus and armpits.

The transversely striated muscles of the skin are the facial muscles.

basement membrane called an electron-dense structure associated with the basal plasma membrane of the epithelial cell, but lying outside the cell (Fig. 1.3.1, 1.3.2).

Rice. 1.3.1. Light-optical (a) and ultrastructural (b) structure of the basement membrane: a - basement membrane (arrow) of the epithelium of the renal tubules; b - ultrastructure of the basement membrane of the anterior epithelium of the cornea (arrow indicates anchor fibrils)

Rice. 1.3.2. Schematic representation of the structure of the basement membrane and hemidesmosome (according to V.L. Bykov, 1999): 1 - light plate; 2 - dense plate; 3 - reticular plate; 4 - plasmalemma; 5 - hemidesmosome; 6 - intermediate filaments; 7-anchor filaments; 8-anchor fibrils; 9 - collagen fibrils

The basement membrane can be very thin, to the extent that it cannot be distinguished by light microscopy. Thick membranes are also found. Thick basement membranes are called " glassy membranes" There are also basement membranes visible to the naked eye (lens capsule).

Thick basement membranes the eyes are a multitude of intertwining thin basement membranes folded into a complex multilayer structure. Stratified basement membranes can be composed of thick laminae (the periphery of the corneal epithelium) or thin laminae (the internal limiting membrane of the ciliated epithelium).

Some basement membranes (lens capsule) have a distinct fibrous structure.

Basement membranes are transparent, have elastic properties, are capable of contraction and collapse when they are destroyed (collapse of Descemet’s membrane after a penetrating wound of the cornea).

Free surfaces of thick glassy-like basement membranes smooth. For this reason, they reflect light intensely. This explains the shiny surface of Descemet's membrane, lens capsule, and retinal limiting membrane.

Ultrastructural studies have revealed that basement membranes have a rather complex structure. They have three layers.

The first layer is the light plate (lamina lucida). This layer has a thickness of 30-50 nm and is adjacent to the plasmalemma of the basal surface of epithelial cells. Thin anchor filaments are directed from the hemidesmosomes of epithelial cells deep into this plate. The light plate contains glycoproteins (including the sulfated glycoprotein laminin) and pemphigus antigen (promoting the attachment of the basal part of epithelial cells), as well as proteoglycans (heparan sulfate).
The second layer is a dense plate (lamina densa). This layer has a thickness of 50-60 nm and consists of granular and fibrillar material. This layer faces the epithelial tissue. Weaved into this plate are anchor fibrils that look like loops (formed by type VII collagen), into which collagen fibrils of the underlying connective tissue are threaded. The lamina densa contains type IV collagen and entactin. heparan sulfate, type V collagen and the adhesive glycoprotein fibronectin.
Third - reticular plate (lamina reticularis) consists of collagen fibrils of connective tissue associated with anchor fibrils. It consists of fibrils formed by collagen types I and III. Although, according to some authors, this plate should not be classified as the basement membrane itself, it forms the bulk of the structure that is revealed by the PAS reaction or staining with silver salts.

The functions of the basement membrane are

maintaining normal architecture, differentiation and polarization of the epithelium;
ensuring a tight connection of epithelial cells with the underlying connective tissue;
selective filtration of nutrients, provision and regulation of epithelial growth along the underlying connective tissue during its development and reparative regeneration.

Violation of the structure and function of the basement membrane leads to the development of a number of organ diseases, including the eyeball (diabetic microangiopathy).