Renal epithelium in urine - what does this mean? Characteristics of various types of integumentary epithelium Some terms from practical medicine

2. From the nephroganotomy

1. Staining: hematoxylin, eosin

provide regeneration);

Stratified squamous non-keratinizing epithelium of the cornea

1. Staining: hematoxylin

2. From ectoderm

3. Consists of layers:

· basal layer

spinous layer

cover cells

4. Lines the anterior (oral cavity, pharynx, esophagus) and final section (anal rectum) of the digestive system, the cornea. Mechanical protection.

Stratified squamous epithelium of the skin

1. Staining: hematoxylin

2. From ectoderm

3. Consists of layers:

· basal layer

spinous layer

granular layer

shiny layer

layer of horny scales

4. Epidermis of the skin. Protection from mechanical damage, radiation, bacterial and chemical exposure, distinguishes the body from the environment.

5. The basal layer contains stem cells for regeneration

Stratified transitional epithelium of the bladder mucosa

1. Staining: hematoxylin, eosin

2. From ectoderm

· basal layer

· intermediate layer

cover cells

4. Lines hollow organs, the wall of which is capable of strong stretching (pelvis, ureters, bladder). Protective.

5. The basal layer contains stem cells for regeneration

Rough fibrous bone tissue. Total preparation of the gill arch of the fish cover

1. Coloring: no.

2. From mesenchyme.

3. Ossein fibers are arranged randomly and disorderly. Osteoblasts and osteocytes are located in the lacunae.

4. Present in cranial sutures, places of attachment of tendons to bones; in the embryonic period, first, in place of the cartilaginous model of the future bone, coarse-fibrous bone is formed, which then becomes fine-fibrous.

Cross section of the diaphysis of a decalcified long bone (tibia)

1. Staining: thionin + picric acid, Schmorl method

2. From mesenchyme

3. 1) Periosteum (periosteum).

2) External general (general) plates - bone plates surround the bone along the entire perimeter, and between them are osteocytes.

3) Osteon layer. Osteon (Haversian system) is a system of 5-20 cylinders of bone plates, concentrically inserted into each other. A blood capillary runs through the center of the osteon. Osteocytes lie between the bone plates-cylinders in the lacunae. The spaces between adjacent osteons are filled with intercalary plates - these are the remains of the decaying old osteons that were here before these osteons.

4) Internal common (general) plates (similar to external ones).

5) Endooste - similar in structure to the periosteum.

4. Regeneration and growth of bone in thickness is carried out due to the periosteum and endosteum.

White adipose tissue

1. No coloring

2. See the rest above

Hyaline cartilage

1. Staining: hematoxylin, eosin

2. From mesenchyme

3. Cells – chondrocytes, chondroblasts, chondroclasts, semi-stem cells, stem cells. Chondrocytes are the main cells, oval-round in shape with basophilic cytoplasm, located in lacunae, forming isogenic groups

Intercellular substance - collagen fibers, elastic fibers and ground substance

Around the isogenic groups there is a clearly defined basophilic zone - the so-called territorial matrix

The weakly oxygenic areas between the territorial matrices are called the interterritorial matrix.

4. Covers all articular surfaces of bones, is contained in the sternal ends of the ribs, in the airways. Support-mechanical, protective.

5. Regeneration thanks to stem and semi-stem cells

Dog cerebellum

1. Color: AgNO 3

2. From the neural tube

3. Layers of bark:

Molecular (stellate and basket cells)

Ganglion (pyriform Purkinje cells)

Granular (granule cells, Golgi cells and spindle cells)

White matter: afferent and efferent fibers

4. Regulation of motor acts

Single-layer cuboidal epithelium of the renal tubules

1. Staining: hematoxylin, eosin

2. From the nephroganotomy

3. Consists of a single layer of sharply flattened cubic cells. When cut, the diameter (width) of the cells is equal to the height.

4. Found in the excretory ducts of the exocrine glands, in the convoluted renal tubules.

5. Regeneration occurs due to stem (cambial) cells, evenly scattered among other differentiated cells.

Single-layer multirow ciliated epithelium of the trachea

1. Staining: hematoxylin, eosin

2. From the endoderm of the epichordal plate

3. All cells are in contact with the basement membrane, but have different heights and therefore the nuclei are located at different levels, i.e. in several rows. Within this epithelium there are different types of cells:

Short and long intercalary cells (poorly differentiated and among them stem cells; provide regeneration);

Goblet cells - have the shape of a glass, do not perceive dyes well (white in the preparation), produce mucus;

- ciliated cells have ciliated cilia on the apical surface.

4. Lines the airways. Purification and humidification of passing air.

Exercise 1. Examine and sketch preparations 1,2,3,4,5.

Drug No. 2. Tall prismatic (cylindrical) epithelium. Rabbit kidney. Hematoxylin-eosin
At low magnification, the kidney tubules are clearly visible, cut in different directions. Depending on how they were cut, the tubules can be in the form of circles or ovals and have a lumen of varying sizes. Connective tissue fibers and blood vessels are visible between the tubules. Under high magnification, you should find a cross section of the renal tubule, where a number of tall cylindrical cells adjacent closely to each other are clearly visible. The cells are located on a thin basement membrane. Cells have basal and apical edges. The nucleus lies closer to the basal part of the cell. Draw a cross-section of one tubule, indicating the listed structures.	Single-layer cylindrical epithelium of the collecting ducts of the kidney: 1- cylindrical cells; 2- basement membrane; 3- connective tissue and vessels surrounding the tubes
Drug No. 3. Low prismatic epithelium. Rabbit kidney. Hematoxylin-eosin.
On the preparation at low magnification, find a cross section of the renal tubules. The size of the lumen may vary. Epithelial cells are arranged in one row and fit very tightly to each other, forming a continuous layer. Determine the shape of epithelial cells by comparing their width and height. Between the cells in the apical part, end plates can be seen. The nuclei are round, large and lie closer to the basal part and almost at the same level. The basement membrane separates the epithelial cells from the underlying connective tissue. Connective tissue contains a large number of blood capillaries. Examine the specimen under high magnification, examine the basement membrane,	Low prismatic epithelium of rabbit renal tubules: 1-lumen of the tubule; 2 – prismatic cells; 3 – basement membrane; 4 – connective tissue and vessels surrounding the tubules. having the appearance of a thin oxyphilic border on the outside of the tubule, consider the cytoplasm and nuclei of epithelial cells. Draw a cross-section of one tubule, indicating the listed structures.

Drug No. 4. Single-layer squamous epithelium (mesothelium). Impregnation with silver nitrate + hematoxylin. Total drug

A total film preparation of the intestinal mesentery, in which the lateral borders of tightly adjacent epithelial cells of irregular shape were revealed by impregnation with silver nitrate. The thinnest parts of the preparation are painted light yellow, and the convoluted borders of the cell (1) are painted black. The cell contains one or two nuclei. This is due to the fact that the mesentery consists of two layers of epithelium, and between them there is a thin layer of connective tissue. Nuclei (2) are counterstained with hematoxylin. Examine the preparation under high magnification and sketch 5-6 cells, indicating the tortuous cell boundaries, nuclei and cytoplasm

Single-layer squamous epithelium (mesothelium) of the omentum: 1-epithelial cells; a-cytoplasm; b-core;

Drug No. 5. Transitional epithelium. Rabbit bladder. Hematoxylin-eosin.

The specimen is a cross-section of the bladder wall. The inside of the wall is lined with transitional epithelium. The epithelial layer forms folds. Examine the preparation at low magnification. The epithelial layer is represented by several layers of cells: the basal layer, the intermediate layer and the superficial layer. The cells of the intermediate layer are of various shapes (round, cubic and irregular polygonal, and on the surface - elongated if the layer is not stretched), some of them are binucleate. The lowest layer of the epithelial layer is separated from the connective tissue by a thin basement membrane.

Transitional epithelium of the bladder (epithelium with an unstretched organ wall): 1- superficial cells with a cuticle on the surface; 2- cells of the intermediate layers of the epithelium; 3- cells of the basal layer of the epithelium; 4- loose connective tissue A blood vessel can be seen located in the loose connective tissue (4).

INDEPENDENT WORK.

Exercise 1. Draw a diagram of the structure of a desmosome, hemidesmosome and its relationship with the basement membrane, noting the main chemical components of these structures.

Task 2. Draw up a diagram of the morphological classification of epithelia, giving relevant examples.

Recommended further reading.

1. Shubnikova E.A. Epithelial tissues.-M.: Publishing house of Moscow State University, 1996.-256 p.

2. Ham A., Cormack D. Histology.-M., Mir, 1983.-T.2.-P.5-34.

Laboratory work No. 2

Topic: Epithelial tissues. Glandular epithelium. Exocrine glands

Purpose of the lesson.

After self-studying theoretical material and working in a practical lesson, the student should know:

1..Characteristics of glandular epithelial cells, features of their structure.

2.Classifications and typical examples of different types of glands.

3. The secretory cycle of glandular epithelial cells, its morphofunctional characteristics and the structure of various types of secretory cells.

Topic study plan

Glandular epithelia

Definitions and classification

Types of secretion

Merocrine

Apocrine

Holocrine

Epithelial tissues, or epithelia (erithelia), cover the surfaces of the body, mucous and serous membranes of internal organs (stomach, intestines, bladder, etc.), and also form most of the glands. In this regard, a distinction is made between the integumentary and glandular epithelia.

Covering epithelium is a border tissue. It separates the body (internal environment) from the external environment, but at the same time participates in the metabolism of the body with the environment, performing the functions of absorbing substances (absorption) and excreting metabolic products (excretion). For example, through the intestinal epithelium, products of food digestion are absorbed into the blood and lymph, which serve as a source of energy and building material for the body, and through the renal epithelium, a number of nitrogen metabolism products are released, which are waste products for the body. In addition to these functions, the integumentary epithelium performs an important protective function, protecting the underlying tissues of the body from various external influences - chemical, mechanical, infectious, etc. For example, the skin epithelium is a powerful barrier to microorganisms and many poisons. Finally, the epithelium covering the internal organs located in the body cavities creates conditions for their mobility, for example, for contraction of the heart, excursion of the lungs, etc.

Glandular epithelium carries out a secretory function, that is, it forms and secretes specific products - secretions that are used in processes occurring in the body. For example, the secretion of the pancreas is involved in the digestion of proteins, fats and carbohydrates in the small intestine.

SOURCES OF DEVELOPMENT OF EPITHELIAL TISSUE

Epithelia develop from all three germ layers starting from the 3rd-4th week of human embryonic development. Depending on the embryonic source, epithelia of ectodermal, mesodermal and endodermal origin are distinguished.

Structure. Epithelia are involved in the construction of many organs, and therefore exhibit a wide variety of morphophysiological properties. Some of them are general, allowing one to distinguish epithelia from other tissues of the body.

Epithelia are layers of cells - epithelial cells (Fig. 39), which have different shapes and structures in different types of epithelium. There is no intercellular substance between the cells that make up the epithelial layer and the cells are closely connected to each other through various contacts - desmosomes, tight junctions, etc. Epithelia are located on basement membranes (lamellas). The basement membranes are about 1 µm thick and consist of an amorphous substance and fibrillar structures. The basement membrane contains carbohydrate-protein-lipid complexes, on which its selective permeability to substances depends. Epithelial cells can be connected to the basement membrane by hemidesmosomes, similar in structure to the halves of desmosomes.

Epithelia do not contain blood vessels. Nutrition of epithelial cells occurs diffusely through the basement membrane from the side of the underlying connective tissue, with which the epithelium is in close interaction. Epithelia have polarity, that is, the basal and apical sections of the entire epithelial layer and its constituent cells have a different structure. Epithelia have a high ability to regenerate. Epithelial restoration occurs due to mitotic division and differentiation of stem cells.

CLASSIFICATION

There are several classifications of epithelia, which are based on various characteristics: origin, structure, function. Of these, the most widespread is the morphological classification, which takes into account the relationship of cells to the basement membrane and their shape on the free, apical (from the Latin apex - apex) part of the epithelial layer (Scheme 2).

In morphological classification reflects the structure of epithelia, depending on their function.

According to this classification, first of all, single-layer and multilayer epithelia are distinguished. In the first, all epithelial cells are connected to the basement membrane, in the second, only one lower layer of cells is directly connected to the basement membrane, and the remaining layers are deprived of such a connection and are connected to each other. According to the shape of the cells that make up the epithelium, they are divided into flat, cubic and prismatic (cylindrical). In this case, in multilayered epithelium, only the shape of the outer layers of cells is taken into account. For example, the epithelium of the cornea is multilayered squamous, although its lower layers consist of prismatic and winged cells.

Single layer epithelium can be single-row or multi-row. In single-row epithelium, all cells have the same shape - flat, cubic or prismatic and, therefore, their nuclei lie at the same level, i.e. in one row. Such an epithelium is also called isomorphic (from the Greek isos - equal). Single-layer epithelium, which has cells of various shapes and heights, the nuclei of which lie at different levels, i.e., in several rows, is called multi-row, or pseudo-stratified.

Stratified epithelium It can be keratinizing, non-keratinizing and transitional. The epithelium in which keratinization processes occur, associated with the transformation of the cells of the upper layers into horny scales, is called multilayered squamous keratinization. In the absence of keratinization, the epithelium is stratified squamous non-keratinizing.

Transitional epithelium lines organs subject to strong stretching - the bladder, ureters, etc. When the volume of an organ changes, the thickness and structure of the epithelium also changes.

Along with morphological classification, it is used ontophylogenetic classification, created by the Soviet histologist N. G. Khlopin. It is based on the peculiarities of the development of epithelia from tissue primordia. It includes epidermal (cutaneous), enterodermal (intestinal), coelonephrodermal, ependymoglial and angiodermal types of epithelium.

Epidermal type The epithelium is formed from the ectoderm, has a multilayer or multirow structure, and is adapted to perform primarily a protective function (for example, stratified squamous epithelium of the skin).

Enterodermal type The epithelium develops from the endoderm, is single-layer prismatic in structure, carries out the processes of absorption of substances (for example, the single-layer bordered epithelium of the small intestine), and performs a glandular function.

Coelonephrodermal type the epithelium is of mesodermal origin, its structure is single-layer, flat, cubic or prismatic, and performs mainly a barrier or excretory function (for example, the flat epithelium of the serous membranes - mesothelium, cubic and prismatic epithelium in the urinary tubules of the kidneys).

Ependymoglial type represented by a special epithelium lining, for example, the cavities of the brain. The source of its formation is the neural tube.

To angiodermal type include the endothelial lining of blood vessels, which is of mesenchymal origin. The structure of the endothelium is single-layer squamous epithelium.

STRUCTURE OF DIFFERENT TYPES OF COVERING EPITHELIA

Single-layer squamous epithelium (epithelium simplex squamosum).
This type of epithelium is represented in the body by endothelium and mesothelium.

Endothelium (entothelium) lines blood and lymphatic vessels, as well as the chambers of the heart. It is a layer of flat cells - endothelial cells, lying in one layer on the basement membrane. Endotheliocytes are distinguished by a relative paucity of organelles and the presence of pinocytotic vesicles in the cytoplasm.

The endothelium is involved in the exchange of substances and gases (O2, CO2) between the blood and other tissues of the body. If it is damaged, it is possible to change the blood flow in the vessels and form blood clots - thrombi - in their lumens.

Mesothelium covers the serous membranes (leaves of the pleura, visceral and parietal peritoneum, pericardial sac, etc.). Mesothelial cells - mesotheliocytes are flat, have a polygonal shape and uneven edges (Fig. 40, A). At the location of the nuclei, the cells are somewhat thickened. Some of them contain not one, but two or even three cores. There are single microvilli on the free surface of the cell. Serous fluid is released and absorbed through the mesothelium. Thanks to its smooth surface, internal organs can glide easily. The mesothelium prevents the formation of connective tissue adhesions between the organs of the abdominal and thoracic cavities, the development of which is possible if its integrity is violated.

Single-layer cubic epithelium (epithelium simplex cubuideum). It lines part of the renal tubules (proximal and distal). Proximal tubule cells have a brush border and basal striations. The striation is due to the concentration of mitochondria in the basal parts of the cells and the presence here of deep folds of the plasmalemma. The epithelium of the renal tubules performs the function of reverse absorption (reabsorption) of a number of substances from primary urine into the blood.

Single-layer prismatic epithelium (epithelium simplex columnare). This type of epithelium is characteristic of the middle section of the digestive system. It lines the inner surface of the stomach, small and large intestines, gallbladder, a number of ducts of the liver and pancreas.

In the stomach, in the single-layer prismatic epithelium, all cells are glandular, producing mucus, which protects the stomach wall from the harsh influence of food lumps and the digestive action of gastric juice. In addition, water and some salts are absorbed into the blood through the epithelium of the stomach.

In the small intestine, a single-layer prismatic (“bordered”) epithelium actively performs the function of absorption. The epithelium is formed by prismatic epithelial cells, among which goblet cells are located (Fig. 40, B). Epithelial cells have a well-defined striated (brush) suction border, consisting of many microvilli. They participate in the enzymatic breakdown of food (parietal digestion) and the absorption of the resulting products into the blood and lymph. Goblet cells secrete mucus. Covering the epithelium, mucus protects it and the underlying tissues from mechanical and chemical influences.

Along with border and goblet cells, there are basal granular endocrine cells of several types (EC, D, S, J, etc.) and apical granular glandular cells. The hormones of endocrine cells released into the blood take part in regulating the function of the digestive system.

Multi-row (pseudostratified) epithelium (epithelium pseudostratificatum). It lines the airways - the nasal cavity, trachea, bronchi, and a number of other organs. In the airways, the multirow epithelium is ciliated, or ciliated. There are 4 types of cells in it: ciliated (ciliated) cells, short and long intercalary cells, mucous (goblet) cells (Fig. 41; see Fig. 42, B), as well as basal granular (endocrine) cells. The intercalary cells are likely stem cells capable of dividing and developing into ciliated and mucous cells.

The intercalary cells are attached to the basement membrane by their wide proximal part. In ciliated cells, this part is narrow, and their wide distal part faces the lumen of the organ. Thanks to this, three rows of nuclei can be distinguished in the epithelium: the lower and middle rows are the nuclei of intercalary cells, the upper row are the nuclei of ciliated cells. The apices of the intercalary cells do not reach the surface of the epithelium, so it is formed only by the distal parts of the ciliated cells, covered with numerous cilia. The mucous cells have a goblet or ovoid shape and secrete mucins onto the surface of the layer.

Dust particles that enter the respiratory tract along with the air settle on the mucous surface of the epithelium and are gradually pushed out by the movement of its ciliated cilia into the nasal cavity and further into the external environment. In addition to ciliated, intercalated and mucous epithelial cells, several types of endocrine, basal granular cells (EC-, P-, D-cells) were found in the epithelium of the airways. These cells secrete biologically active substances into the blood vessels - hormones, with the help of which local regulation of the respiratory system is carried out.

Stratified squamous non-keratinized epithelium (epithelium stratificatum squamosum noncornificatum). Covers the outside of the cornea of ​​the eye, lining the oral cavity and esophagus. There are three layers distinguished in it: basal, spinous (intermediate) and flat (superficial) (Fig. 42, A).

Basal layer consists of prismatic epithelial cells located on the basement membrane. Among them there are stem cells capable of mitotic division. Due to the newly formed cells entering differentiation, the epithelial cells of the overlying layers of the epithelium are replaced.

Layer spinosum consists of cells of irregular polygonal shape. In the basal and spinous layers in epithelial cells, tonofibrils (tonofilament bundles) are well developed, and between epithelial cells there are desmosomes and other types of contacts. The upper layers of the epithelium are formed by flat cells. Having completed their life cycle, they die and fall off the surface of the epithelium.

Stratified squamous keratinizing epithelium (epithelium stratificatum squamosum cornificatum). Covers the surface of the skin, forming its epidermis, in which the process of transformation (transformation) of epithelial cells into horny scales occurs - keratinization. At the same time, specific proteins (keratins) are synthesized in the cells and accumulate more and more, and the cells themselves gradually move from the lower layer to the overlying layers of the epithelium. In the epidermis of the skin of the fingers, palms and soles, 5 main layers are distinguished: basal, spinous, granular, shiny and horny (Fig. 42, B). The skin of the rest of the body has an epidermis in which there is no shiny layer.

Basal layer consists of cylindrical epithelial cells. In their cytoplasm, specific proteins are synthesized that form tonofilaments. This is where stem cells are located. Stem cells divide, after which some of the newly formed cells differentiate and move to the overlying layers. Therefore, the basal layer is called germinal, or germinal (stratum germinativum).

Layer spinosum formed by polygonal-shaped cells that are firmly connected to each other by numerous desmosomes. In place of desmosomes on the surface of cells there are tiny projections - “spines” directed towards each other. They are clearly visible when intercellular spaces expand or when cells shrink. In the cytoplasm of spinous cells, tonofilaments form bundles - tonofibrils.

In addition to epithelial cells, the basal and spinous layers contain process-shaped pigment cells - melanocytes, containing granules of the black pigment - melanin, as well as epidermal macrophages - dendrocytes and lymphocytes, which form a local immune surveillance system in the epidermis.

Granular layer consists of flattened cells, the cytoplasm of which contains tonofibrils and keratohyalin grains. Keratohyalin is a fibrillar protein that can subsequently be converted into eleidin in the cells of the overlying layers, and then into keratin - the horny substance.

Shiny layer formed by flat cells. Their cytoplasm contains highly refractive eleidin, which is a complex of keratohyalin with tonofibrils.

Stratum corneum very powerful in the skin of the fingers, palms, soles and relatively thin in other areas of the skin. As cells move from the stratum lucidum to the stratum corneum, their nuclei and organelles gradually disappear with the participation of lysosomes, and the complex of keratohyalin with tonofibrils turns into keratin fibrils and the cells become horny scales, shaped like flat polyhedra. They are filled with keratin (horny substance), consisting of densely packed keratin fibrils, and air bubbles. The outermost horny scales, under the influence of lysosome enzymes, lose contact with each other and constantly fall off the surface of the epithelium. They are replaced by new ones due to the proliferation, differentiation and movement of cells from the underlying layers. The stratum corneum of the epithelium is characterized by significant elasticity and poor thermal conductivity, which is important for protecting the skin from mechanical influences and for the processes of thermoregulation of the body.

Transitional epithelium (epithelium transitionale). This type of epithelium is typical of urinary drainage organs - renal pelvis, ureters, bladder, the walls of which are subject to significant stretching when filled with urine. It contains several layers of cells - basal, intermediate, superficial (Fig. 43, A, B).

Basal layer formed by small round (dark) cells. The intermediate layer contains cells of various polygonal shapes. The surface layer consists of very large, often bi- and trinuclear cells, having a dome-shaped or flattened shape, depending on the condition of the organ wall. When the wall is stretched due to the filling of the organ with urine, the epithelium becomes thinner and its surface cells flatten. During contraction of the organ wall, the thickness of the epithelial layer increases sharply. In this case, some cells in the intermediate layer are “squeezed out” upward and take on a pear-shaped shape, and the surface cells located above them take on a dome-shaped shape. Tight junctions are found between superficial cells, which are important for preventing the penetration of fluid through the wall of an organ (for example, the bladder).

Regeneration. The integumentary epithelium, occupying a border position, is constantly influenced by the external environment, so the epithelial cells wear out and die relatively quickly.

The source of their restoration is epithelial stem cells. They retain the ability to divide throughout the life of the organism. While multiplying, some of the newly formed cells begin to differentiate and turn into epithelial cells similar to the lost ones. Stem cells in multilayer epithelia are located in the basal (primordial) layer; in multilayer epithelia these include intercalary (short) cells; in single-layer epithelia they are located in certain areas, for example, in the small intestine in the epithelium of the crypts, in the stomach in the epithelium of the necks of the own glands and etc. The high ability of the epithelium for physiological regeneration serves as the basis for its rapid restoration under pathological conditions (reparative regeneration).

Vascularization. The integumentary epithelia do not have blood vessels, with the exception of the stria vascularis of the inner ear. Nutrition to the epithelium comes from vessels located in the underlying connective tissue.

Innervation. The epithelium is well innervated. It contains numerous sensitive nerve endings - receptors.

Age-related changes. With age, a weakening of renewal processes is observed in the integumentary epithelium.

STRUCTURE OF GLONUS EPITHELIA

The glandular epithelium (epithelium glandulare) consists of glandular, or secretory, cells - glandulocytes. They carry out the synthesis, as well as the release of specific products - secretions onto the surface of the skin, mucous membranes and in the cavities of a number of internal organs [external (exocrine) secretion] or into the blood and lymph [internal (endocrine) secretion].

Through secretion, many important functions are performed in the body: the formation of milk, saliva, gastric and intestinal juice, bile, endocrine (humoral) regulation, etc.

Most glandular cells with external secretion (exocrine) are distinguished by the presence of secretory inclusions in the cytoplasm, a developed endoplasmic reticulum, and a polar arrangement of organelles and secretory granules.

Secretion (from the Latin secretio - separation) is a complex process that includes 4 phases:

1. absorption of starting products by glandulocytes,
2. synthesis and accumulation of secretions in them,
3. secretion from glandulocytes - extrusion
4. and restoration of their structure.

These phases can occur in glandulocytes cyclically, that is, one after another, in the form of the so-called secretory cycle. In other cases, they occur simultaneously, which is typical for diffuse or spontaneous secretion.

First phase of secretion lies in the fact that various inorganic compounds, water and low-molecular organic substances enter the glandular cells from the blood and lymph from the basal surface: amino acids, monosaccharides, fatty acids, etc. Sometimes larger molecules of organic substances penetrate into the cell by pinocytosis, for example proteins.

In the second phase From these products, secretions are synthesized in the endoplasmic reticulum, protein secretions with the participation of the granular endoplasmic reticulum, and non-protein secretions with the participation of the agranular endoplasmic reticulum. The synthesized secretion moves through the endoplasmic reticulum to the zone of the Golgi complex, where it gradually accumulates, undergoes chemical restructuring and is formed in the form of granules.

In the third phase the resulting secretory granules are released from the cell. Secretion is released differently, and therefore three types of secretion are distinguished:

• merocrine (eccrine)
• apocrine
• holocrine (Fig. 44, A, B, C).

With the merocrine type of secretion, glandular cells completely retain their structure (for example, cells of the salivary glands).

With the apocrine type of secretion, partial destruction of glandular cells (for example, mammary gland cells) occurs, i.e., along with secretory products, either the apical part of the cytoplasm of glandular cells (macroapocrine secretion) or the tips of microvilli (microapocrine secretion) are separated.

The holocrine type of secretion is accompanied by the accumulation of fat in the cytoplasm and the complete destruction of glandular cells (for example, cells of the sebaceous glands of the skin).

Fourth phase of secretion consists in restoring the original state of glandular cells. Most often, however, the restoration of cells occurs as they are destroyed.

Glandulocytes lie on the basement membrane. Their shape is very diverse and varies depending on the phase of secretion. The kernels are usually large, with a rugged surface, which gives them an irregular shape. In the cytoplasm of glandulocytes, which produce protein secretions (for example, digestive enzymes), a granular endoplasmic reticulum is well developed.

In cells that synthesize non-protein secretions (lipids, steroids), an agranular cytoplasmic reticulum is expressed. The Golgi complex is extensive. Its shape and location in the cell change depending on the phase of the secretory process. Mitochondria are usually numerous. They accumulate in places of greatest cell activity, i.e. where secretions are formed. The cytoplasm of cells usually contains secretory granules, the size and structure of which depend on the chemical composition of the secretion. Their number fluctuates depending on the phases of the secretory process.

In the cytoplasm of some glandulocytes (for example, those involved in the formation of hydrochloric acid in the stomach), intracellular secretory tubules are found - deep invaginations of the cytolemma, the walls of which are covered with microvilli.

The cytolemma has a different structure on the lateral, basal and apical surfaces of cells. On the lateral surfaces it forms desmosomes and tight junctions (terminal bridges). The latter surround the apical (apical) parts of the cells, thus separating the intercellular gaps from the lumen of the gland. On the basal surfaces of cells, the cytolemma forms a small number of narrow folds that penetrate the cytoplasm. Such folds are especially well developed in the cells of the glands that secrete secretions rich in salts, for example in the duct cells of the salivary glands. The apical surface of the cells is covered with microvilli.

Polar differentiation is clearly visible in glandular cells. It is due to the direction of secretory processes, for example, during external secretion from the basal to the apical part of the cells.

GLANDS

Glands (glandulae) perform a secretory function in the body. Most of them are derivatives of glandular epithelium. The secretions produced in the glands are important for the processes of digestion, growth, development, interaction with the external environment, etc. Many glands are independent, anatomically designed organs (for example, the pancreas, large salivary glands, thyroid gland). Other glands are only part of the organs (for example, the glands of the stomach).

Glands are divided into two groups:

1. endocrine glands, or endocrine glands
2. exocrine glands, or exocrine (Fig. 45, A, B, C).

Endocrine glands produce highly active substances - hormones that enter directly into the blood. That is why these glands consist only of glandular cells and do not have excretory ducts. These include the pituitary gland, pineal gland, thyroid and parathyroid glands, adrenal glands, pancreatic islets, etc. All of them are part of the body’s endocrine system, which, together with the nervous system, performs a regulatory function.

Exocrine glands produce secretions that are released into the external environment, i.e., onto the surface of the skin or into organ cavities lined with epithelium. In this regard, they consist of two parts:

1. secretory, or terminal, sections (pirtiones terminalae)
2. excretory ducts (ductus excretorii).

The terminal sections are formed by glandulocytes lying on the basement membrane. The excretory ducts are lined with different types of epithelia depending on the origin of the glands. In the glands developing from the enterodermal epithelium (for example, in the pancreas), they are lined with single-layer cubic or prismatic epithelium, and in the glands developing from the ectodermal epithelium (for example, in the sebaceous glands of the skin), they are lined with stratified non-keratinizing epithelium. Exocrine glands are extremely diverse, differing from each other in structure, type of secretion, i.e., the method of secretion and its composition.

The listed characteristics form the basis for the classification of glands. Based on their structure, exocrine glands are divided into the following types (Scheme 3).

Simple glands have a non-branching excretory duct, complex glands - branching (see Fig. 45, B). It opens into it in unbranched glands one at a time, and in branched glands into several terminal sections, the shape of which can be in the form of a tube or a sac (alveolus) or an intermediate type between them.

In some glands derived from ectodermal (stratified) epithelium, for example in salivary glands, in addition to secretory cells, there are epithelial cells that have the ability to contract - myoepithelial cells. These cells, which have a process form, cover the terminal sections. Their cytoplasm contains microfilaments containing contractile proteins. Myoepithelial cells, when contracting, compress the end sections and, therefore, facilitate the release of secretions from them.

The chemical composition of the secretion may be different; therefore, the exocrine glands are divided into

• proteinaceous (serous)
• mucous membranes
• protein-mucosal (see Fig. 42, D)
• greasy.

In mixed glands, two types of secretory cells may be present - protein and mucous. They form either separately end sections (purely proteinaceous and purely mucous), or together mixed end sections (proteinaceous and mucous). Most often, the composition of the secretory product includes protein and mucous components with only one of them predominant.

Regeneration. In the glands, in connection with their secretory activity, processes of physiological regeneration constantly occur.

In merocrine and apocrine glands, which contain long-lived cells, restoration of the original state of glandulocytes after secretion from them occurs through intracellular regeneration, and sometimes through reproduction.

In holocrine glands, restoration is carried out through the proliferation of special stem cells. The newly formed cells are then transformed into glandular cells through differentiation (cellular regeneration).

Vascularization. The glands are abundantly supplied with blood vessels. Among them there are arteriole-venular anastomoses and veins equipped with sphincters (closing veins). Closing the anastomoses and sphincters of the closing veins leads to an increase in pressure in the capillaries and ensures the release of substances used by glandulocytes to form secretions.

Innervation. Carried out by the sympathetic and parasympathetic nervous system. Nerve fibers follow the connective tissue along the blood vessels and excretory ducts of the glands, forming nerve endings on the cells of the terminal sections and excretory ducts, as well as in the walls of blood vessels.

In addition to the nervous system, the secretion of the exocrine glands is regulated by humoral factors, i.e., hormones of the endocrine glands.

Age-related changes. In old age, changes in the glands can manifest themselves in a decrease in the secretory activity of glandular cells and changes in the composition of secretions produced, as well as a weakening of regeneration processes and the proliferation of connective tissue (gland stroma).

Continuation. beginning see N o 33/2001

Laboratory workshop on human anatomy, physiology and hygiene

(9th grade chemical and biological profile)

Laboratory work N o 5.
Microscopic structure of tissues

Target: give an idea of ​​the structure of tissues (epithelial, connective, muscle, nervous).

Equipment: histological preparations, microscopes.

PROGRESS

Epithelial tissue

Single-layer epithelia (Fig. 1)

1. Single-layer columnar epithelium (collective a tube kidneys)
At low magnification of the microscope, find rounded hollow formations on the preparation - cross sections of renal tubules lined with single-layer epithelium.
Turn the microscope to high magnification, examine the structure of one renal tubule, pay attention to the single-layered epithelial layer (all cells lie on the basal membrane), the height of the cells (cubic or cylindrical depending on the width of the lumen of the tubule), the various shapes of the nuclei and their location, to the basal membrane membrane and connective tissue underlying the epithelium.

2. Single layer flat epithelium (mesothelium oil seal a rabbit)
Examine the microscopic specimen first at low and then at high magnification. Note the structural features of this tissue (shape of cells, their location, features of their connection).

3. Flickering epithelium (epithelium mucous membrane) (Fig. 2)
Examine the microscopic specimen at low magnification. Pay attention to the presence of eyelashes.

Rice. 2. Single-layer multirow prismatic ciliated epithelium of the nasal mucosa:
1 – ciliated cells; 2–3 – goblet cells; 4 – replacement cells; 5 – basement membrane

4. Glandular epithelium (green gland cancer)
Examine the microscopic specimen first at low and then at high magnification. Note the presence of goblet cells.

Reporting form

Draw the main structures of single-layer epithelium, indicating all the listed details of its structure.

Stratified epithelia (Fig. 3)

A – stratified squamous epithelium of the cornea; B – stratified squamous epithelium of the skin; C – transitional epithelium (a – in a stretched and b – in a collapsed organ); 1–3 – epithelial layer; stk – connective tissue; c – cylindrical layer; o – layer of spinous cells; h – granular layer; b – shiny layer; r – the stratum corneum itself

1. Multilayer flat epithelium (cornea of ​​the eye)
At low magnification, examine the layer of cells covering the cornea of ​​the eye. Please note that the cells lie in several layers, on top of each other, and only the bottom layer is on the basement membrane.
Turn the microscope to high magnification. Consider the shape of cells in different layers of the epithelium (prismatic, polygonal with processes, and flat with flattened nuclei).

2. Transitional epithelium (uric bunny bubble) (Fig. 4).
Examine the microscopic specimen first at low magnification. At high magnification, examine the shape of cells in different layers of the epithelium. Note the features of the transitional epithelium (shape and size of cells, location features).

Rice. 4. Transitional epithelium of the rabbit bladder:
I – asleep; II – slightly stretched; III – in a highly distended bladder

Reporting form

Draw the stratified epithelium in your notebook. Indicate the similarities and differences in the structure of single-layer and multilayer epithelium.

Connective tissue

Loose (areolar) tissue (Fig. 5)

Rice. 5. Loose, unformed connective tissue of the rabbit’s subcutaneous tissue:
1 – endothelium; 2 – adventitial (cambial) cell; 3 – fibroblast; 4 – histiocyte; 5 – fat cell

At low microscope magnification, look for an area on the specimen with a loose arrangement of structural elements.
Turn the microscope to high magnification and examine the shape of the cells (large star-shaped with light nuclei - fibroblasts, round or retracted, with dark nuclei - histiocytes) and the structure of the intercellular substance (straight or winding ribbons - collagen fibers and thin, branching threads forming a network - elastic fibers).

Reporting form

Draw the main structural elements of loose connective tissue.

To be continued

Unfamiliar terms in tests and medical reports often frighten patients. What does the detected renal epithelium in the urine indicate? You will find the answer in our article.

A little physiology

The kidneys are one of the most complex organs in the human body. The excretory system also includes the ureters, urethra and bladder.

The outside of the kidney is covered by a capsule of dense connective tissue. This shell reliably protects against mechanical stress. Kidney tissue consists of a cortical (outer) and medulla (inner) layer.

Main functions of the organ:

• release and reabsorption of electrolytes (sodium, potassium and calcium);
• maintaining acid-base balance;
• participation in metabolic processes (breakdown of amino acids and peptides and gluconeogenesis);
• removal of excess fluid, metabolic end products and toxins from the body;
• kidneys take part in the formation of many hormones.

The main structural and functional unit of the kidney is the nephron.

Components:

1. Renal corpuscle(tangle of capillaries and capsule covering it). Urine is filtered into the glomerular cavity.
2. Proximal straight and convoluted tubules.
3. Nephron loop.
4. Distal convoluted and straight tubules.
5. Collecting ducts that open into the calyces of the kidney.

1500 liters of blood pass through the excretory system per day, resulting in the formation of primary urine in the amount of 180 liters. Then partial reabsorption of water and electrolytes occurs.

The epithelium of the renal tubule is single-layered, in the proximal part of the nephron it is cubic bordered, in the distal part it is prismatic and low (which ensures less wall thickness). Normally, the kidneys are impermeable to blood cells and large-molecular plasma proteins.

Let's look into the microscope

The epithelium is a layer of cells lining the cavities of internal organs. Its structure varies depending on the function performed.

Epithelium properties:

• the cells are located on the basement membrane and lack blood capillaries;
• nutrition of the epithelium is carried out by diffusion from the underlying layer of connective tissue;
• small amount of intercellular substance;
• epithelia are polar - there are apical (upper) and basal (base) parts;
• able to quickly recover in case of damage.

Passing through the excretory system, the fluid interacts with the wall of the urinary tract. This is why epithelial cells can always be found in urine. To diagnose a pathological condition, the number and type of cells detected are important.

If the indicator exceeds ten cells in the field of view, one may suspect:

• inflammatory process of the genitourinary system;
• consequences of taking antibacterial drugs;
• mechanical damage to the urethral wall or (medical manipulation, rough sex).

Epithelium of the urinary system

Kinds:

Diseases

Frequent reasons for changes in urine analysis are an inflammatory process in the genitourinary system.

Cystitis

Pyelonephritis

Glomerulonephritis

Urolithiasis disease

The photos and videos in this article will tell you about the diagnosis of diseases of the excretory system.

Frequently asked questions to the doctor

Examination of pregnant women

Hello, Doctor! I'm 12 weeks pregnant. I donated urine. Finally, there are squamous epithelial cells, there are a lot of them. This is scary?

Good afternoon.

Norms for pregnant women:

• squamous epithelium– up to five cells in the field of view;
• transition– single cells;
• renal- must not be.

To evaluate the tests, a consultation with a urologist is necessary.

Unfamiliar terms

Good afternoon I took a urine test. In the conclusion it is written that renal epithelium was detected. This is serious? The urologist said it was very bad and ordered a bunch of additional tests. I read on the Internet - there can’t be no epithelium in the kidneys at all!

Hello! Renal epithelial cells in the urine are an alarming sign indicating damage to the parenchyma.