Single-layer cubic or prismatic epithelium of the renal tubules. Practical work in class. Human community, its distinctive features

The kidney is covered with a capsule that has two layers and consists of collagen fibers with a slight admixture of elastic fibers, and a layer of smooth muscles in depth. The latter directly pass into the muscle cells of the stellate veins. The capsule is penetrated by blood and lymphatic vessels, closely connected with the vascular system of not only the kidney, but also the perinephric tissue. The structural unit of the kidney is the nephron, which includes the glomerulus together with the Shumlyansky-Bowman capsule (together constituting the renal corpuscle), convoluted tubules of the first order, loop of Henle, convoluted tubules of the second order, straight tubules and collecting ducts that open into the calyces of the kidney (color table , Fig. 1 - 5). The total number of nephrons is up to 1 million.

Rice. 1. Frontal section of the kidney (diagram): 1 - capsule; 2-cortical substance; 3 - medulla (Malpighi pyramids); 4 - renal pelvis.
Rice. 2. Section through the kidney lobe (low magnification): 1 - capsule; 2 - cortex; 3 - transversely cut convoluted urinary tubules; 4 - longitudinally cut straight urinary tubules; 5 - glomeruli.

Rice. 3. Section through a section of the cortex (high magnification): 1 - glomerulus; 2 - outer wall of the glomerular capsule; 3 - main section of the urinary tubule; 4 - intercalary section of the urinary tubule; 5 - brush border.
Rice. 4. Section through the superficial part of the medulla (high magnification): 1 - thick section of the loop of Henle (ascending limb); 2 - thin section of the loop of Henle (descending limb).
Rice. 5. Incision through the deep part of the medulla (high magnification). Collecting tubes.

The glomerulus is formed by blood capillaries into which the afferent arteriole breaks up. Collecting into a single outflow tract, the capillaries of the glomerulus give rise to the efferent arteriole (vas efferens), the caliber of which is much narrower than the efferent arteriole (vas afferens). The exception is the glomeruli located on the border between the cortical and medulla layers, in the so-called juxtamedullary zone. Juxtamedullary glomeruli are larger in size, and the caliber of their afferent and efferent vessels is the same. Due to their location, the juxtamedullary glomeruli have a special circulation that is different from that of the cortical glomeruli (see above). The basement membrane of the glomerular capillaries is dense, homogeneous, up to 400 Å thick, and contains PAS-positive mucopolysaccharides. Endothelial cells are often vacuolated. Electron microscopy reveals round holes in the endothelium up to 1000 Å in diameter, in which blood is in direct contact with the basement membrane. The capillary loops seem to be suspended on a kind of mesentery - the mesangium, which is a complex of hyaline plates made of proteins and mucopolysaccharides, between which there are cells with small nuclei and scanty cytoplasm. The glomerulus of capillaries is covered with flat cells up to 20-30 microns in size with light cytoplasm, which are in close contact with each other and make up the inner layer of the Shumlyansky-Bowman capsule. This layer is connected to the capillaries by a system of channels and lacunae in which provisional urine filtered from the capillaries circulates. The outer layer of the Shumlyansky-Bowman capsule is represented by flat epithelial cells, which at the point of transition to the main section become taller and cubic. In the area of the vascular pole of the glomerulus there are a special kind of cells that form the so-called endocrine apparatus of the kidney - the juxtaglomerular apparatus. One of these cells - granular epithelioid - are located in 2-3 rows, forming a sleeve around the afferent arteriole just before its entrance into the glomerulus. The number of granules in the cytoplasm varies depending on the functional state. Cells of the second type - small, flat, elongated, with a dark nucleus - are placed in the angle formed by the afferent and efferent arterioles. These two groups of cells, according to modern views, arise from smooth muscle elements. The third variety is a small group of tall, elongated cells with nuclei located at different levels, as if piled on top of each other. These cells belong to the place of transition of the loop of Henle into the distal convoluted tubule and, based on the dark spot formed by piled-up nuclei, are designated as macula densa. The functional significance of the juxtaglomerular apparatus is reduced to the production of renin.

The walls of convoluted tubules of the first order are represented by cubic epithelium, at the base of which the cytoplasm has radial striations. Parallel rectilinear, highly developed folds of the basement membrane form a kind of chamber containing mitochondria. The brush border in the epithelial cells of the proximal nephron is formed by parallel protoplasmic filaments. Its functional significance has not been studied.

The loop of Henle has two limbs: a descending thin limb and an ascending thick one. They are lined with flat epithelial cells, light, well-receptive to aniline dyes, with a very weak granularity of the cytoplasm, which sends few and short microvilli into the lumen of the tubule. The border of the descending and ascending limbs of the loop of Henle corresponds to the location of the macula densa of the juxtaglomerular apparatus and divides the nephron into proximal and distal sections.

The distal part of the nephron includes convoluted tubules of the second order, practically indistinguishable from the convoluted tubules of the first order, but lacking a brush border. Through a narrow section of straight tubules they pass into collecting ducts, lined with cuboidal epithelium with light cytoplasm and large light nuclei. The collecting ducts open through 12-15 passages into the cavity of the small calyces. In these areas, their epithelium becomes high cylindrical and passes into the double-row epithelium of the calyces, and the latter into the transitional epithelium of the urinary pelvis. The proximal part of the nephron is responsible for the main reabsorption of glucose and other substances that have a high absorption threshold, while the distal part is responsible for the absorption of the main amount of water and salts.

The muscular layer of the calyces and pelvis is closely connected with the muscles of the inner layer of the kidney capsule. The fornices of the kidneys (fornices) are devoid of muscle fibers, are represented mainly by the mucous and submucosal layers and therefore are the most vulnerable place of the upper urinary tract. Even with a slight increase in intrapelvic pressure, ruptures of the renal vaults with a breakthrough of the contents of the pelvis into the kidney substance can be observed - the so-called pyelorenal refluxes (see).

The intervening connective tissue in the cortex is extremely scarce and consists of thin reticular fibers. In the medulla it is more developed and also includes collagen fibers. There are few cellular elements in the stroma. The stroma is densely permeated with blood and lymphatic vessels. The renal arteries have a microscopically clear division into three membranes. The intima is formed by endothelium, the ultrastructure of which is almost similar to that in the glomeruli, and so-called subendothelial cells with fibrillar cytoplasm. Elastic fibers form a powerful internal elastic membrane - two or three layers. The outer shell (wide) is represented by collagen fibers with an admixture of individual muscle fibers, which, without sharp boundaries, pass into the surrounding connective tissue and muscle bundles of the kidney. In the adventitia of the arterial vessels there are lymphatic vessels, of which the large ones also contain oblique muscle bundles in their wall. In the veins, three membranes are conventional, their adventitia is almost not expressed.

The direct connection between arteries and veins is represented in the kidneys by two types of arteriovenous anastomoses: direct connection of arteries and veins during the juxtamedullary circulation and arteriovenous anastomoses such as closing arteries. All renal vessels - blood and lymphatic - are accompanied by nerve plexuses, which form along their course a thin branched network, ending in the basement membrane of the renal tubules. A particularly dense nerve network entwines the cells of the juxtaglomerular apparatus.

Study of the process of regulation of water-salt metabolism and local true blood circulation in the human body. Study of the characteristics of the blood supply to the kidney, the structure and regeneration of the cortical and juxtamedullary nephrons, and the work of the endocrine part of the kidney.

HISTOLOGY OF THE URINARY SYSTEM

The urinary system contains the kidneys and urinary tract. The main function is excretory, and is also involved in the regulation of water-salt metabolism.

The endocrine function is well developed, regulates local true blood circulation and erythropoiesis. Both in evolution and in embryogenesis there are 3 stages of development.

At the beginning, the preference is formed. From the segmental legs of the anterior sections of the mesoderm, tubules are formed, the tubules of the proximal sections open as a whole, the distal sections merge and form the mesonephric duct. The kidney exists for up to 2 days, does not function, dissolves, but the mesonephric duct remains.

Then the primary bud is formed. From the segmental legs of the trunk mesoderm, urinary tubules are formed, their proximal sections, together with blood capillaries, form renal corpuscles - urine is formed in them.

Kidney cysts histology

The distal sections empty into the mesonephric duct, which grows caudally and opens into the primary gut.

In the second month of embryogenesis, a secondary or final kidney is formed. Nephrogenic tissue is formed from the unsegmented caudal mesoderm, from which the renal tubules are formed and the proximal tubules participate in the formation of renal corpuscles. The distal ones grow, from which nephron tubules are formed. From the urogenital sinus behind, from the mesonephric duct, an outgrowth is formed in the direction of the secondary kidney, from which the urinary tract develops, the epithelium is a multilayer transitional one. The primary kidney and mesonephric duct are involved in the construction of the reproductive system.

The outside is covered with a thin connective tissue capsule. The kidney contains a cortical substance, it contains renal corpuscles and convoluted renal tubules, inside the kidney there is a medulla in the form of pyramids. The base of the pyramids faces the cortex, and the apex of the pyramids opens into the renal calyx. There are about 12 pyramids in total.

The pyramids consist of straight tubules, descending and ascending tubules, nephron loops and collecting ducts. Some of the straight tubules in the cortex are located in groups, and such formations are called medullary rays.

The structural and functional unit of the kidney is the nephron; in the kidney, cortical nephrons predominate, most of them are located in the cortex and their loops penetrate shallowly into the medulla, the remaining 20% are juxtamedullary nephrons. Their renal corpuscles are located deep in the cortex on the border with the medulla. The nephron is divided into a corpuscle, a proximal convoluted tubule, and a distal convoluted tubule.

The proximal and distal tubules are built from convoluted tubules.

Nephron structure

The nephron begins with the renal body (Bowman-Shumlyansky), it includes the vascular glomerulus and the glomerular capsule. The afferent arteriole approaches the renal corpuscle. It breaks up into capillaries, which form a vascular glomerulus; the blood capillaries merge, forming an efferent arteriole, which leaves the renal corpuscle.

The glomerular capsule contains an outer and an inner leaf. Between them there is a capsule cavity. The inside of the cavity is lined with epithelial cells - podocytes: large branched cells, which with processes are attached to the basement membrane. The inner leaf penetrates the vascular glomerulus and envelops all blood capillaries from the outside. In this case, its basement membrane merges with the basement membrane of the blood capillaries to form one basement membrane.

The inner layer and the wall of the blood capillary form a renal barrier (the composition of this barrier includes: a basement membrane, it contains 3 layers, its middle layer contains a fine network of fibrils and podocytes. The barrier into the hole allows all the formed elements to pass through: large molecular blood proteins (fibrins, globulins , part of albumins, antigen-antibody).

After the renal corpuscle comes the convoluted tubule; it is represented by a thick tubule, which is twisted several times around the renal corpuscle; it is lined with a single-layer cylindrical marginal epithelium, with well-developed organelles.

Then comes a new loop of nephron. The distal convoluted tubule is lined with cubic epithelium with sparse microvilli, wraps several times around the renal corpuscle, then passes through the vascular glomerulus, between the afferent and efferent arterioles, and opens into the collecting duct.

The collecting ducts are straight tubules lined with cubic and columnar epithelium, in which light and dark epithelial cells are distinguished. The collecting ducts merge to form papillary canals, two of which open at the top of the medullary pyramids.

Features of the blood supply to the kidney

The renal artery enters the portal of the organ, which breaks up into interlobar arteries, they break up into arcuate arteries (at the border of the cortex and medulla). From them interlobular arteries leave into the cortex, they in turn break up into intralobular ones, from which afferent arterioles depart, which break up into the primary capillary network, they form a vascular glomerulus. Then comes the efferent arteriole. In cortical nephrons, the lumen of the efferent arteriole is 2 times narrower than that of the afferent arteriole. This impedes the outflow of blood and creates high blood pressure in the capillaries of the glomerulus, necessary for the filtration process.

Histophysiology of the cortical nephron

As a result of the high blood flow in the capillaries of the glomerulus, blood plasma is filtered through the renal barrier, which (normally) does not allow blood cells and large molecular proteins to pass through. The filtrate, which is close in composition to blood serum (contains nitrogenous wastes, etc.), enters the cavity of the capillary glomerulus and is called primary urine (approximately 100-150 liters per day).

Primary urine then enters the proximal tubule of the nephron. From primary urine, with the help of microvilli, glucose and proteins are absorbed into the cells, which are captured by lysosomes and hydrolytic enzymes break down proteins into amino acids. Electrolytes and water are also absorbed. 80% of primary urine is absorbed proximally. All these substances enter the interstitium through the basement membrane, then pass through the wall of the secondary capillary network, and return to the body through the venous vessels. This process is called reabsorption. In the proximal region, complete, obligate reabsorption of electrolytes and water occurs. Normally, there are no proteins and glucose in the urine; if they are present, then the disturbances are in the proximal section.

Next, primary urine enters the descending tubule of the nephron loop, lined with squamous epithelium, where water is reabsorbed. The ascending parts of the nephron loop are lined with cubic epithelium with a small content of microvilli; reabsorption of electrolytes (mainly sodium) occurs. This process continues in the convoluted tubule of the distal nephron.

The remainder of the primary urine enters the collecting ducts, where the reabsorption of water is completed with the help of light epithelial cells, and this occurs with the participation of the antideuretic hormone. Dark epithelial cells secrete hydrochloric acid, and acidification of the urine occurs. Secondary urine is formed in an amount of 1.5-2 liters, which contains water, electrolytes and nitrogenous waste.

kidney blood circulation nephron endocrine

Histophysiology of juxtamedullary nephrons

Unlike cortical nephrons, the diameter of the efferent and afferent arterioles is the same, so the blood pressure in the capillary glomeruli is low. The secondary capillary network is very poorly developed. Through the vascular network of these nephrons, excess blood entering the kidney is discharged. Urination may be inhibited.

Nephron regeneration

After birth, new nephrons are not formed; restoration is carried out due to compensatory nephron hypertrophy. at the same time, the renal corpuscle increases in size and the tubules of the surviving nephron lengthen. Regeneration of the epithelium of the nephron tubules occurs due to the proliferation and differentiation of stem cells, which are located in the glomerular capsule at the border with the distal part.

Endocrine part of the kidney

It consists of the renin or juxtagromerular apparatus. It produces the hormone renin, which stimulates the conversion of angiotensinogen to angiotensin. Angiotensin increases blood pressure and stimulates the production of aldosterone.

The apparatus includes juxtaglomerular cells - these are large oval-shaped cells located in the walls of the afferent and efferent arterioles under the endothelium. They produce and release renin into the blood. This process is enhanced by insufficient sodium reabsorption.

The device also includes the macula densa - part of the wall of the distal tubule of the nephron between the afferent and efferent arterioles and facing the choroid glomerulus. Contains tall epithelial columnar cells. The basement membrane in this area is poorly developed or absent. These cells respond to changes in sodium concentration in the primary urine, and this information is transmitted to the juxtaglomerular cells. This apparatus includes juxtabasal cells; they are located between the macula densa, arterioles and the vascular glomerulus. They contain large, oval, irregularly shaped process cells that are involved in the transmission of information about sodium concentration by juxtagromerular cells and are themselves capable of producing renin.

The medulla contains interstitial cells; they are located across the straight tubules and with their processes cover the tubules of the nephron loops and the vessels of the secondary capillary network. They secrete the hormones prostaglandins and bradykinin, which cause a decrease in blood flow and dilation of blood vessels.

The epithelium of the convoluted tubule produces callicrinip, which controls the formation of kinins, which in turn stimulate blood flow and urine production.

The juxtaglomerular apparatus produces erythropoietins, which stimulate erythropoiesis in the red bone marrow.

Urinary tract

These include the renal calyces, renal pelvis, ureters, bladder and urethra. They have a common structure. There are mucous membrane, submucous layer, muscular layer and outer layer (adventitia).

Histophysiology of the ureter

The mucosa and submucosa form small longitudinal folds: there is mucus on the surface.

The mucous membrane is covered with transitional epithelium - uroepithelium. Underneath it there is a lamina of the mucosa of loose connective tissue, which passes into the submucosa. There is no muscular plate of mucosa. In the lower third of the ureter there are submucosal glands that open onto the surface of the uroepithelium.

The muscle layer is made of smooth muscle tissue. The inner layer is longitudinal, the outer layer is circular. In the lower third, another outer longitudinal layer is delivered. There is no circular layer at the mouth of the ureter.

The outer shell is adventitial.

Histophysiology of the bladder

The mucosa and submucosa form a network of small folds. The muscular layer is wider and contains 3 layers. Smooth muscle cells with a large number of processes are capable of greatly stretching. The cells are arranged in bundles, between which wide layers of loose connective tissue develop.

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Histology kidney preparation

The adventitial plexus contains myelinated and unmyelinated nerve fibers. The nerve plexuses of the bladder contain a significant number of ganglia and single neurons. Among the neurocytes, along with typical motor neurons, there are also receptor neurocytes (Dogel type II cells).

Urethra females contain three membranes: mucous, muscular and adventitia. The inner part of the mucous membrane is composed of multilayered prismatic (in places transitional) epithelium. In mare and sheep it is multi-layered and flat. In pigs and herbivores, the epithelium forms invaginations of varying depths. The lamina propria consists of connective tissue rich in elastic fibers. In the muscular lining of the female urethra there is an internal longitudinal layer and an external circular layer, consisting of separate muscle bundles.

The male urethra from the bladder to the middle of the canal is lined with transitional epithelium, which gives way to multilayered prismatic epithelium, which in its final part becomes multilayered squamous. The lamina propria contains mucous glands and venous plexuses, which pass into the cavernous bodies of the urethra. The muscularis mucosa contains two layers of smooth muscle cells: the inner layer is longitudinal and the outer layer is circular. In the area of the internal opening of the urethra they enter the sphincter of the bladder.

Bird buds are represented by three lobes, each of which is divided into cortical and medullary lobules. The branches of the ureter, forming a large number of collecting ducts, form lobules of the medulla. The branches of the latter penetrate into the cortex of the kidney.

The cortex is formed by individual cortical lobules, with large interlobular veins passing between them. Lobules with a wide base

Rice. 307. Scheme of the structure of the kidney lobule in a chicken:

1 - capsule; 2 - cortical lobule; 3 - intralobular efferent vein; 4 - collecting duct; 5- medullary tubules; 6 - brain loop; 7 - secondary branches of the ureter; 8 - primary branch of the ureter; 9 - ureter.

Rice. 308. Isolated medullary (A) and cortical (B) chicken renal tubules:

1 - proximal nephron; 2- intercalary part of the nephron; 3 - renal corpuscle; 4 - connecting part of the nephron; 5 - nephron loop; 6 — thin loop elbow; 7 - thick loop elbow; 8 - cortical collecting duct.

facing the surface of the kidneys, and the apex to their medulla. One lobule of the medulla corresponds to several cortical lobules. The collecting ducts coming from the medulla surround the cortical lobule from the outside (Fig. 307).

In the center of the cortical lobule there pass the intralobular vein and the terminal sections of the renal arteries.

In the parenchyma of the avian kidney, two types of nephrons can be distinguished: cortical and medullary. Cortical nephrons are located within the cortical lobules, while medullary nephrons are mainly localized in the medulla of the organ. Brain nephrons, in their position in the organ and structure, correspond to the nephrons of the kidneys of mammals. They consist of a capsule of the glomerulus and sections: proximal, transferring (thin), distal, intercalary and connecting (Fig. 308-A). Cortical nephrons are less tortuous, and their loop does not have a thin section (B). They are morphologically closer to the tubules of reptile kidneys.

The renal corpuscles of the cortical nephrons are concentrated in the center of the lobule near the interlobular vein. Their vascular pole faces the intralobular vein, and the urinary pole faces the periphery of the lobule.

The renal corpuscles of the cerebral nephrons lie in the region of the apex of the cortical lobule. The convoluted section of the medullary nephron can partially penetrate the medulla. The medullary nephron loop extends far beyond the cortex, penetrating parallel to the collecting ducts. The bend of the loop is formed by the thick part of the nephron. The nephron tubule returns to its renal corpuscle and passes into the thin connecting part.

Chicken kidneys receive arterial blood through their own artery from the abdominal aorta and venous blood, which quantitatively exceeds arterial blood, from the caudal-mesenteric, internal iliac and external iliac veins.

Bird ureters have mucous, muscular and serous membranes. The epithelium of the mucous membrane is multirow ciliated with goblet cells. There is a lot of lymphoid tissue in the lamina propria of the mucous membrane. The muscular layer in the initial part of the ureter consists of two layers: internal - longitudinal and external - circular. In the cloaca area there are three layers of smooth muscle cells: in addition to the named layers, there is also an outer longitudinal layer.

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Kidney histology

Histology. Lecture No. 7 Excretory system

Histology. Lecture No. 7

Excretory system.

It is divided into the urinary tract (kidneys) and the urinary tract (renal calyces, pelvis, ureters, bladder, urinary tract).

Kidney functions: exo- and endocrine. The weight of each kidney is 150 g. The kidneys process up to 1700 liters of blood per day. In intensity, blood circulation exceeds all other organs by 20 times. Every 5-10 minutes the entire mass of blood enters the kidneys.

The most important function is the removal of products that are not absorbed by the body (nitrogenous waste). The kidneys are the purgatory of the blood. Urea, uric acid, creatinine - the concentration of these substances is much higher than in the blood. Without the excretory function, there would be inevitable poisoning of the body.

Ensuring homeostasis of the body and blood. It is carried out by regulating the amount of water and salts - maintaining water-salt balance. Regulate acid-base balance and electrolyte content. The kidneys prevent the amount of water from exceeding the norm and adapt to changing conditions. Depending on the needs of the body, the acidity level can be changed from 4.4 to 6.8 pH.

Endocrine. They synthesize renin and prostaglandins.

Regulation of hematopoiesis. Stimulates the formation of erythropoietin in plasma.

Neutralizes toxic substances in case of liver failure.

If kidney function is impaired, uremia, acidosis, edema, etc. occur.

EMBRYONAL DEVELOPMENT.

Three stages. 3 paired organs are formed sequentially:

1. Pre-kidney - pronephros (pre-kidney)

2. Primary kidney - mesonephros (Wolffian body).

3. The final kidney is metanephros.

The source of development is nephrotom.

The forebud is formed from 8-10 segments of legs corresponding to the head end of the embryo.

They then develop into convoluted tubules, which form the mesonephric duct. The kidney exists for 40 hours and does not function.

The primary bud is formed from 25 leg segments. They separate from the somite and grow to the downward growing mesonephric duct. At the other end, afferent arterioles from the aorta grow towards them and renal corpuscles form. By 4-5 months, the primary kidney ceases to exist.

From the 2nd month, differentiation of the permanent kidney occurs. Formed from 2 sources:

nephrogenic rudiment - a section of mesoderm not divided into leg segments, which is located in the caudal part of the embryo. Nephrons are formed from it.

Mesonephric duct - gives rise to collecting ducts, papillary tubules, calyces, pelvis, ureters.

Kidney structure.

The periphery is covered with a connective tissue membrane (capsule). In front - the visceral layer of the peritoneum.

Consists of 2 parts: cortex and medulla.

The medulla is divided into 8-12 pyramids, ending in papillary tubules that open into calyces.

The cortex, penetrating into the medulla, forms pyramids. In turn, the medulla, penetrating into the cortex, forms rays.

The structural and functional unit is the nephron (more than 1 million). Its length is 15-150 mm, total up to 150 km.

Formed by the glomerular capsule, consisting of a visceral and parietal layer; proximal section - convoluted and straight parts; descending section of the loop; distal section - convoluted and straight parts. The distal section flows into the collecting duct, which does not enter the nephron.

There are 2 types of nephrons: cortical (80%, of which only 1% are truly cortical) and pericerebral (juxtamedullary - 20%).

Cortical nephrons are renal corpuscles and proximal parts in the cortex, and the loop, straight tubules are in the medulla.

Juxtamedullary nephrons are located at the border. The loop is completely in the cortex.

The cortex is formed by renal corpuscles, proximal and distal sections.

The medulla is a loop and collecting ducts.

The kidney is divided into lobes, the number of which corresponds to the number of pyramids. The lobe is a pyramid of the medulla with adjacent cortical.

Lobules are also released. Correspond to parts of the organ in which all nephrons open into one collecting duct. Interlobular arteries and veins pass along the periphery.

BLOOD SUPPLY.

Peculiar. Associated with the presence of 2 types of nephrons.

Renal artery - lobar arteries - arcuate arteries (between the cortex and medulla) - interlobular arteries - intralobular artery - afferent arteriole - primary hemocapillary network (in the cortical nephron) - efferent arteriole (its larger diameter) - secondary hemocapillary network.

The primary network is called the miraculous network, the secondary network entwines all the tubules (reabsorption).

Then the venous network, stellate vein - interlobular veins - arcuate veins - lobar veins - renal vein.

In the cerebral nephron, the diameter of the afferent and efferent arterioles is the same. Part of the blood is discharged into direct venules - arcuate veins - lobar veins - renal vein.

The cerebral nephron takes part in urine formation during physical activity.

HISTOPHYSIOLOGY OF THE NEPHRON.

There are 3 stages in urine formation: filtration, reabsorption (obligate and facultative), secretion (acidification of urine).

FILTRATION. It occurs in the renal corpuscles. They are oval in shape, diameter 150-200 microns. They consist of a vascular glomerulus and 2 capsule layers (internal, external). Between them is a cavity where primary urine (ultrafiltrate) enters.

There are approximately 50 capillaries in the glomerulus, which are lined with fenestrating endothelial cells and form anastomoses. Endothelial cells have pores, most of which are not covered by the diaphragm (reminiscent of a sieve). Outside there is a basement membrane, which is common with the epithelium of the inner layer of the capsule. Consists of 3 layers: peripheral ones are less dense, central dense. Epithelial cells of the inner layer of the capsule take part in the formation, which completely changes within 1 year. The cells of the inner layer of the capsule have processes 0 cytotrabeculae, cytopodia, which are in close contact with the basement membrane.

Here is the filtration barrier:

porous endothelial cells

basement membrane

podocytes

it has selective permeability. The renal corpuscle contains mesangiocytes. They synthesize intercellular substance, participate in immune reactions, and perform an endocrine function (renin production).

The outer layer of the capsule is formed by flat nephrocytes. Between the 2 leaves is a cavity where primary urine enters (170 liters per day). The filtration barrier is permeable to water, glucose, sodium salts, potassium, phosphorus, low molecular weight proteins (albumin), and slag substances. Do not pass: blood cells, proteins with high molecular weight (fibrinogen, immune bodies).

Filtration occurs due to high pressure due to the difference in diameters of the efferent and afferent arterioles.

REABSORPTION. Occurs in the peritubular space, and then in the vessels. It starts from the proximal nephron, which is formed by single-layer cuboidal epithelium. The lumen is uneven, lined with a brush border. On the opposite side of the cells there is basal striation (cytolemma folds, mitochondria). Here, obligate reabsorption of glucose, 85% of water, 85% of salts, proteins occurs (absorbed on the apical surface of cells by pinocytosis. Pinocytosis vesicles merge with lysosomes, where the protein is broken down into amino acids and enters the cytoplasm and then into the blood).

On the surface of the brush border - alkaline phosphatase - glucose reabsorption. When blood glucose levels rise, it is not completely reabsorbed.

Reabsorption of electrolytes and water is associated with the folds of the basal plasmalemma and mitochondria. It happens passively. Nephrocytes of the proximal part perform an excretory function (metabolic products, dyes, drugs).

Further in the nephron loop there is facultative reabsorption. The thin part of the loop is formed by single-layer squamous epithelium. On the inner surface on the basal side there are folds of the cytolemma. There are a small number of microvilli on the surface.

Water reabsorption continues. At the bottom of the loop, the solution becomes hypertonic. As the liquid rises up the loop, sodium is pumped out. This area is waterproof. The solution becomes isotonic. It comes to the distal part in the rectum. The epithelium is single-layered, cubic. On the basal side there is striation (mitochondria, folds). This is where sodium reabsorption continues. The solution becomes hypotonic. In the surrounding tissues there is a hypertonic solution. Sodium reabsorption is promoted by the hormone aldosterone. A hypotonic solution enters the collecting ducts. Water reabsorption occurs, facilitated by antidiuretic hormone. In its absence, the wall of the collecting duct is impermeable to water - a lot of urine is released from the body. The collecting ducts are formed by a single-layer cubic, prismatic epithelium of 2 types of cells - light and dark. Light ones perform endocrine functions (prostaglandins) and water reabsorption.

Acidification of urine occurs in dark cells.

ENDOCRINE SYSTEM.

There are 2 devices: renin and prostaglandin.

JGA (juxtaglomerular apparatus). In YUGA there are 4 components:

JG cells of the afferent arteriole. These are modified muscle cells that secrete renin.

Cells of the macula densa of the distal nephron. The epithelium is prismatic, the basement membrane is thinned, and the number of cells is large. This is the sodium receptor.

Juxtavascular cells. They are located in a triangular space. between the afferent and efferent arterioles.

Mesangiocytes. Capable of producing renin when JH cells are depleted.

The regulation of the renin apparatus is carried out: when blood pressure decreases, the afferent arterioles do not stretch (JH cells are baroreceptors) - increased secretion of renin. They act on plasma globulin, which is synthesized in the liver. Angiotensin-1 is formed, consisting of 10 amino acids. In the blood plasma, 2 amino acids are separated from it and angiotensin-2 is formed, which has a vasoconstrictor effect. Its effect is twofold:

directly acts on arterioles, contracting smooth muscle tissue - increasing pressure.

Stimulates the adrenal cortex (aldosterone production).

Affects the distal parts of the nephron, retains sodium in the body.

All this leads to increased blood pressure. YUGA can cause a persistent increase in blood pressure; it produces a substance that is converted into erythropoietin in the blood plasma.

Prostaglandins. Presented:

interstitial cells of the medulla. These are branched cells.

Light cells of the collecting ducts.

Prostaglandins have antihypertensive effects. Renin antagonists.

Kidney cells extract from the blood the pro-hormone vitamin D3 produced in the liver, which is converted into vitamin D3, which stimulates the absorption of calcium and phosphorus.

The physiology of the kidneys depends on the functioning of the urinary tract. If their conductivity is disrupted, renal colic occurs.

URINARY TRACT. Consist of 4 shells:

incomplete mucosa is formed by transitional epithelium and lamina propria

submucosal layer

muscular layer (2, 3 layers: inner, outer layer - longitudinal, middle - circular)

the outer shell is adventitial. There are areas that are formed by the serous membrane.

Lecture notes for universities are published with the permission of the copyright holder: scientific book literary agency, head of the editorial office of medical literature gitun t.

Abstract

1. Histology is the science of the microscopic and submicroscopic structure, development and vital activity of tissues of animal organisms. Consequently, histology studies one of the levels of organization of living tissue matter.
Lecture 1: “Definition of the subject, objectives and content. History of the development of veterinary therapy"

Lecture

Veterinary medicine, veterinary medicine (from the Latin veterinarius - caring for livestock, treating livestock), a complex of sciences that study animal diseases, as well as a system of measures aimed at their prevention and elimination, protection of the population
Educational and methodological manual for medical university students on histology and cytology with the basics of embryology

Educational and methodological manual

Educational and methodological manual for medical university students on histology and cytology with the basics of embryology: textbook. allowance / [P.A. Motavkin et al.
Master's program "Vertebrate Zoology" The place of vertebrate zoology among modern biological sciences. System

Program

The lancelet is a modern representative of the cephalochordate subphylum - the simplest “model” of chordates. Key features of the organization of chordates, reflecting the fundamental stages in the history of the evolutionary formation of the type.
Work program for the academic discipline histology, cytology and embryology

Working programm

The goals of mastering the academic discipline (module) Histology, cytology and embryology are to prepare students for further study of morphological disciplines: pathological anatomy and clinical cytology.

3. Histological structure of the kidneys.

URETER, BLADDER, URETHA

capsule and interstitial connective tissue

capsule formed from dense fibrous connective tissue
interstitial (intraorgan) connective tissue formed by loose fibrous connective tissue

represented by nephrons

NEPHRON - structural and functional unit of the kidney, consists of the renal corpuscle and a tube extending from it, in which there are several sections: the proximal convoluted tubule, the proximal straight tubule, the loop of nephron (loop of Henle), consisting of a descending thin tubule and an ascending thick tubule (also called distal straight tubule), distal convoluted tubule and collecting duct, the renal parenchyma is divided into the cortex and medulla, some parts of the same nephron lie in the cortex, and others in the medulla; in the cortex there are renal corpuscles, proximal convoluted and straight tubules, distal convoluted tubules, the initial parts of the collecting ducts, in the medulla there are loops of nephrons and the distal parts of the collecting ducts; the nephron begins blindly in the region of the renal corpuscle, and the collecting duct opens into the renal calyx and beyond - into the renal pelvis; in the renal corpuscle, primary urine is filtered, which then enters the proximal convoluted tubule, proximal straight tubule, nephron loop, distal convoluted tubule and collecting duct; while primary urine flows through the tubules, various substances and water needed by the body are absorbed from it by the epithelial cells of the tubules, that is, the process of reverse absorption or reabsorption occurs in the tubules, while the urine is concentrated and is called secondary urine; another process can take place in the tubules - secretion, in which certain substances are secreted by epithelial cells into the lumen of the tubule and thus enter the urine

renal corpuscle formed by the choroid glomerulus and the double-walled glomerular capsule

The CAPSULE consists of inner and outer layers, the outer layer is formed by single-layer squamous epithelium, the inner one is made of cells - podocytes; the inner layer surrounds the capillaries of the vascular glomerulus and shares a basement membrane with them; Podocytes, among other functions, form the basement membrane and participate in its renewal
The vascular glomerulus consists of capillaries, the capillaries are fenestrated, the basement membrane is common to both the capillary and the inner layer of the capsule; the basement membrane is thick, three-layered; The capillaries of the glomerulus are formed due to the branching of the afferent arteriole; when leaving the renal corpuscle, the capillaries are connected to form the efferent arteriole
THE CAVITY OF THE CAPSULE communicates with the lumen of the proximal convoluted tubule; primary urine is filtered into the capsule cavity, which from the capsule cavity immediately enters the proximal convoluted tubule
RENAL FILTER - the barrier between blood and primary urine consists of: 1) fenestrated endothelium of the capillaries of the vascular glomerulus; 2) a thick three-layer basement membrane and 3) podocytes - cells of the inner layer of the capsule (see figure below)
MESANGIUM - the area located between the capillaries, where they are not covered with podocytes; the mesangium is formed by loose connective tissue containing slightly modified fibroblasts, called mesangial cells, they participate in the renewal of the basement membrane of capillaries and podocytes, can form its new components and phagocytose old ones
FUNCTION OF THE RENAL BODY - formation (filtration) of primary urine

proximal convoluted tubule formed by single-layer prismatic bordered epithelium; epithelial cells have microvilli on the apical surface and radial striations in the basal part of the cells

proximal straight tubule has the same structure as the proximal convoluted

loop of nephron (loop of Henle) consists of descending and ascending parts

the descending part and the initial part of the ascending part are formed by single-layer squamous epithelium, they are also called thin tubule

ascending part (or thick tubule, or distal straight tubule) formed by single-layer cuboidal epithelium

distal convoluted tubule formed by single-layer cuboidal epithelium

collecting duct in the initial sections it is formed by single-layer cuboidal epithelium, in the final sections - by single-layer prismatic epithelium

RENAL FILTER

(endocrine apparatus)

dense spot- a section of the distal convoluted tubule passing near the renal corpuscle in the area between the afferent and efferent arterioles; the epithelial cells of this area record the concentration of sodium ions in the lumen of the tubule, that is, in the urine; and the sodium concentration in urine reflects the sodium concentration in the blood; when the concentration of sodium in the blood decreases, the level of sodium in the urine also decreases; in this case, the cells of the macula densa give a signal to the juxtaglomerular cells to produce renin
juxtaglomerular cells are located under the endothelium in the afferent and efferent arterioles, are modified smooth muscle cells, produce renin, which catalyzes the formation of angiotensin II from angiotensin I
juxtavascular cells (Gurmaktig cells) located in the connective tissue between the afferent and efferent arterioles and the macula densa, the exact function of these cells is unknown, they may produce erythropoietin

renal artery is divided into two large branches, which are divided into several interlobar arteries, they go between the renal pyramids to the border between the cortex and medulla, where they are divided into arcuate arteries, running parallel to the surface of the kidney; extend from them into the cortex interlobular (radial) arteries, from which they branch afferent arterioles; each afferent arteriole branches to form capillary glomerulus of the renal corpuscle, upon exiting the renal corpuscle, the capillaries unite to form efferent arteriole, which:

in cortical nephrons breaks up into a secondary peritubular capillary network that supplies blood to the tubules; then the capillaries either first turn into superficial ones stellate veins, and then in interlobular veins, or immediately to interlobular veins, then follow arcuate veins
in juxtamedullary nephrons goes straight to straight artery, going into the medulla, where capillaries extend from it to the nephron loops; straight arteries reach the deepest parts of the medulla, then rise to the border between the cortex and medulla and flow into arcuate veins

in cortical nephrons, the afferent arteriole has a larger diameter than the efferent arteriole; therefore, in order for blood to flow through the renal corpuscle in the cortical nephrons, a minimum blood pressure of about 70 mm Hg is required.
if blood flows through the renal corpuscle, it means filtration is taking place and there is urine
if blood does not flow through the renal corpuscle, there is no filtration and no urine
if there is no urine, then blood does not pass through the renal corpuscle and does not reach the secondary periagnal capillary network and the tubules are not supplied with blood, necrosis of the tubules and renal corpuscle occurs - all this is called acute renal failure, and it is necessary to urgently establish blood flow in the kidney

nephrogenic tissue (unsegmented segmental legs of the caudal part of the embryo)- renal corpuscle capsule, nephron tubules
mesonephric (Wolffian) duct- collecting ducts, renal calyces, renal pelvis, ureter
mesenchyme- stroma, vessels

Renal epithelium in urine: what tests will tell you

Probably each of us has taken a general urine test at least once in our lives. Despite the fact that this examination method is considered routine and is prescribed for almost all diseases, it can tell a lot about the condition of the kidneys and the body as a whole. Renal epithelium is one of the parameters that is determined during the analysis. What is it, why is it found in urine, and how much should be normal: we’ll look at it in our detailed review.

Where does the epithelium in urine come from?

Epithelium is small cells that line the mucous membrane of any organ and have barrier (protective) functions. The tissue of the organs of the urinary system is also covered with epithelium, which, depending on the structure, location and functions, is:

Flat - lines the urethra, or urethra. It is observed in urine in single quantities. A significant increase in squamous epithelium in the analysis indicates an inflammatory disease - urethritis.
Transitional - covers the walls of the bladder, ureters, renal pelvis. Normally, this formed element is rarely detected in urine, 1-2 in the field of view. A sharp increase in its quantity indicates the development of cystitis, pyelonephritis, urolithiasis or prostatitis.
Renal - lines the tubules of the kidneys, in which the formation and further transport of primary urine occurs. Normally, it is not contained in the urinary residue at all.
An increase in its concentration almost always indicates that the kidney is affected by infectious or autoimmune inflammation.

The appearance of epithelium in the TAM is associated with the peculiarities of accumulation and release of unnecessary fluid from the body. After formation and reabsorption, urine collects in the renal pelvis, then travels through the ureters to the bladder and accumulates there. During urination, the bladder sphincter relaxes, and waste fluid is freely released from the body.

As urine passes through all organs of the urethra, it can “catch” exfoliating epithelial cells. Normally, there are few such cells, and their content in urine remains single. Inflammation or tissue damage provokes rapid death of the epithelium and its massive excretion along with urine. Therefore, the detection of a large number of epithelial cells in the analysis is a sure sign of the disease.

Note! In girls and women, the source of squamous epithelium in the urine is not only the urethra, but also the vagina, therefore the norm of this type of formed elements in them is increased to 10 in the p/z. Normal values for renal epithelium remain unchanged for both men and women. The exception is newborn babies who have not reached one month of age. The detection of this type of formed elements in their urine is not considered pathological and is associated with physiological changes in the kidneys - transient uric acid diathesis.

Standards of analysis

Thus, the reference values of the renal epithelium are:

in newborns (days 1-28 of life) -1-10 in p/z;
in children and adults they are not detected.

Reasons for detecting renal epithelium in urine

The detection of renal epithelium in urinary sediment is just a symptom that can be characteristic of many diseases. Below we consider common pathologies accompanied by this laboratory sign.

Nephrotic syndrome

Nephrotic syndrome is a serious disease with various development mechanisms, which, in addition to a large amount of renal epithelium in the urine, manifests itself:

severe proteinuria – excretion of large amounts of protein in the urine;
massive swelling;
violation of fat metabolism;
arterial hypertension.

Glomerulonephritis

Glomerulonephritis is an autoimmune lesion of the glomeruli of the kidneys, which is associated with the formation of autoantibodies and an attack of the body’s own defense system of healthy kidney tissue. As with nephrotic syndrome, the laboratory picture shows:

a significant increase in protein in excreted urine;
the appearance of altered red blood cells in it;
the color of urine acquires a characteristic dirty-brown tint (“the color of meat slop”);
blood dysproteinemia and the appearance of massive oncotic edema.

Glomerulopathies

There are congenital and acquired glomerulopathies. Congenital ones, such as Alport syndrome (progressive destruction of renal tissue accompanied by acoustic neuritis) are rare.

Acquired glomerulopathies are a consequence of the toxic effects of infectious agents, certain medications, and ultraviolet radiation. Highlight:

post-infectious;
rapidly progressive;
subacute;
chronic glomerulopathies.

Tubulointerstitial nephritis

Tubulointerstitial nephritis is a disease characterized by damage to the intercellular substance and tubules of the kidney. Its main manifestation is acute renal failure, accompanied by urinary retention. During the recovery stage of diuresis, a large amount of renal epithelium is released.

Metabolic kidney disorders

Kidney pathology associated with metabolic disorders is provoked by systemic diseases such as diabetes mellitus and amyloidosis. Leads to disruption of blood supply, slow death of organ parenchyma and the release of large amounts of renal epithelium in the urine.

Kidney transplant rejection

This complication occurs if a patient who has undergone a kidney transplant does not accept the donor organ, and its rejection begins - the destruction of tissue by the immune system.

The renal epithelium is of great importance in the diagnosis of diseases of the urinary system. Detection of this type of formed elements in the urine is an indication for further examination of the kidneys (ultrasound, excretory urography, CT or MRI). The sooner the pathology is identified, the more successful the treatment results will be, and the laboratory parameters will return to normal faster.

Single layer squamous epithelium represented in the body by endothelium and mesothelium. Mesothelium covers the serous membranes (leaves of the pleura, peritoneum and pericardium). Its cells - mesotheliocytes - lie in one layer on the basement membrane, they are flat, have a polygonal shape and uneven edges. Serous fluid is released and absorbed through the mesothelium, which facilitates the movement and sliding of organs (heart, lungs, abdominal organs). Endothelium lines blood vessels, lymphatic vessels and the heart. It is a layer of flat cells - endothelial cells, lying in one layer on the basement membrane. Only they come into contact with the blood and through them, in the blood capillaries, the exchange of substances between blood and tissues occurs.

Single layer cuboidal epithelium lines part of the renal tubules. It is a layer of cubic cells lying in one layer on the basement membrane. The epithelium of the renal tubules performs the function of reabsorption of a number of substances from primary urine into the blood.

Single layer prismatic epithelium It is a layer of prismatic (cylindrical) cells lying in one layer on the basement membrane. This epithelium lines the inner surface of the stomach, intestines, gallbladder, a number of ducts of the liver and pancreas, and some kidney tubules. In the single-layer prismatic epithelium lining the stomach, all cells are glandular, producing mucus, which protects the stomach wall from damage and the digestive action of gastric juice. The intestine is lined with a single layer of prismatic bordered epithelium, which ensures the absorption of nutrients. To do this, numerous outgrowths are formed on the apical surface of its epithelial cells - microvilli, which together form a brush border.

Single-layer multirow (pseudostratified) epithelium lines the airways: nasal cavity, trachea, bronchi. This epithelium is ciliated, or flickering ( its eyelashes can move quickly in one plane - flicker). It consists of cells of different sizes, the nuclei of which lie at different levels and form several rows - therefore it is called multirow. It only seems that it is multi-layered (pseudo-layered). But it is single-layered, since all its cells are connected to the basement membrane. There are several types of cells in it:

A) ciliated(ciliated) cells; the movement of their cilia removes dust particles that enter the respiratory tract along with the air;

b) mucous membranes(goblet) cells secrete mucus onto the surface of the epithelium, performing a protective function;

V) endocrine, these cells release hormones into the blood vessels;

G) basal(short intercalary) cells are stem and cambial, capable of dividing and turning into ciliated, mucous and endocrine cells;

d) long insert, lie between the ciliated and goblet, performing supporting and supporting functions.

Stratified squamous non-keratinizing epithelium covers the outside of the cornea of the eye, lines the oral cavity, esophagus, and vagina. There are three layers in it:

A) basal the layer consists of prismatic-shaped epithelial cells located on the basement membrane. Among them there are stem and cambial cells capable of mitotic division (due to the newly formed cells, epithelial cells are replaced above the underlying layers of the epithelium);

b) spiny(intermediate) layer consists of cells of irregular polygonal shape, interconnected by desmosomes;

V) flat(superficial) layer - finishing their life cycle, these cells die and fall off the surface of the epithelium.

Stratified squamous keratinizing epithelium(epidermis) covers the surface of the skin. The epidermis of the skin of the palms and soles has a significant thickness and there are 5 main layers:

A) basal the layer consists of prismatic shaped epithelial cells containing keratin intermediate filaments in the cytoplasm; there are also stem and cambial cells, after the division of which, some of the newly formed cells move to the overlying layers;

b) spiny layer - formed by polygonal-shaped cells that are firmly connected to each other by numerous desmosomes; the tonofilaments of these cells form bundles - tonofibrils, granules with lipids appear - keratinosomes;

V) grainy the layer consists of flattened cells, the cytoplasm of which contains grains of the protein filaggrin and keratolinin;

G) brilliant the layer is formed by flat cells that lack nuclei and organelles, and the cytoplasm is filled with the protein keratolinin;

d) horny the layer consists of postcellular structures - horny scales; they are filled with keratin (horny substance) and air bubbles; the outermost horny scales lose contact with each other and fall off the surface of the epithelium, and they are replaced by new cells from the basal layer.

Stratified transitional epithelium lines the urinary tract (calyces and pelvis of the kidneys, ureters, bladder), which are subject to significant stretching when filled with urine. It distinguishes the following cell layers: a) basal; b) intermediate; c) superficial. When stretched, the cells of the superficial layer are flattened, and the cells of the intermediate layer are embedded between the basal ones; at the same time, the number of layers decreases.

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

Drug No. 1. Multilayered squamous epithelium. Cornea of the eye. Hematoxylin–eosin.

At low magnification, look at the two parts. One is colored blue-violet - this is multilayered epithelium, the second part is represented by connective tissue, and is colored pink. Between them you can see a fairly thick uncolored layer - this is the basement membrane. At high magnification, you can count from 10 to 13 rows of cells. The lowest layer is formed by one row of prismatic cells with an oval-shaped nucleus and is connected to the basal membrane using hemidesmosomes. Stem cells and differentiating cells are found here. Then there are cells of almost cubic shape. Wedged between them are spiny cells of irregular polygonal shape with rounded nuclei.

Multilayered squamous (non-keratinizing) epithelium of the cornea: 1- flat cells of the apical layer; 2- cells of the middle layer; 3- cells of the basal layer; 4- basement membrane; 5- corneal substance (connective tissue) The following rows gradually flatten. Light spaces – intercellular gaps – are clearly visible between the cells. These cells slough off over time. There are no blood vessels in the epithelial layers.

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 various 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 communicate between the body and the external environment. They perform integumentary and glandular (secretory) functions.

The epithelium is located in the skin, lines the mucous membranes of all internal organs, is part of the serous membranes and lines the cavities.

Epithelial tissues perform various functions - absorption, excretion, perception of irritations, secretion. Most of the body's glands are made of epithelial tissue.

All germ layers take part in the development of epithelial tissues: ectoderm, mesoderm and endoderm. For example, the epithelium of the skin of the anterior and posterior sections of the intestinal tube is a derivative of ectoderm, the epithelium of the middle section of the gastrointestinal tube and respiratory organs is of endodermal origin, and the epithelium of the urinary system and reproductive organs is formed from mesoderm. Epithelial cells are called epithelial cells.

The main general properties of epithelial tissues include the following:

1) Epithelial cells fit tightly to each other and are connected by various contacts (using desmosomes, closure bands, gluing bands, slits).

2) Epithelial cells form layers. There is no intercellular substance between the cells, but there are very thin (10-50 nm) intermembrane gaps. They contain the intermembrane complex. Substances entering and secreted by cells penetrate here.

3) Epithelial cells are located on the basement membrane, which in turn lies on loose connective tissue that nourishes the epithelium. basement membrane up to 1 micron thick, it is a structureless intercellular substance through which nutrients come from blood vessels located in the underlying connective tissue. Both epithelial cells and loose connective underlying tissue participate in the formation of basement membranes.

4) Epithelial cells have morphofunctional polarity or polar differentiation. Polar differentiation is the different structure of the surface (apical) and lower (basal) poles of the cell. For example, at the apical pole of some epithelial cells, the plasma membrane forms an absorptive border of villi or ciliated cilia, and the basal pole contains the nucleus and most organelles.

In multilayer layers, the cells of the superficial layers differ from the basal ones in shape, structure and function.

Polarity indicates that different processes occur in different parts of the cell. The synthesis of substances occurs at the basal pole, and at the apical pole absorption, movement of cilia, and secretion occur.

5) Epithelia have a well-expressed ability to regenerate. When damaged, they quickly recover through cell division.

6) There are no blood vessels in the epithelium.

Classification of epithelia

There are several classifications of epithelial tissues. Depending on the location and function performed, two types of epithelia are distinguished: integumentary and glandular .

The most common classification of integumentary epithelium is based on the shape of the cells and the number of their layers in the epithelial layer.

According to this (morphological) classification, integumentary epithelia are divided into two groups: I) single-layer and II) multi-layer .

IN single-layer epithelia the lower (basal) poles of the cells are attached to the basement membrane, and the upper (apical) poles border on the external environment. IN stratified epithelia only the lower cells lie on the basement membrane, all the rest are located on the underlying ones.

Depending on the shape of the cells, single-layer epithelia are divided into flat, cubic and prismatic, or cylindrical . In squamous epithelium, the height of the cells is much less than the width. This epithelium lines the respiratory sections of the lungs, the cavity of the middle ear, some sections of the renal tubules, and covers all the serous membranes of the internal organs. Covering the serous membranes, epithelium (mesothelium) participates in the secretion and absorption of fluid into the abdominal cavity and back, and prevents the fusion of organs with each other and with the walls of the body. By creating a smooth surface of the organs lying in the chest and abdominal cavity, it provides the possibility of their movement. The epithelium of the renal tubules is involved in the formation of urine, the epithelium of the excretory ducts performs a delimiting function.

Due to the active pinocytotic activity of squamous epithelial cells, substances are rapidly transferred from the serous fluid to the lymphatic bed.

The single-layer squamous epithelium covering the mucous membranes of organs and serous membranes is called lining.

Single layer cuboidal epithelium lines the excretory ducts of the glands, kidney tubules, and forms the follicles of the thyroid gland. The height of the cells is approximately equal to the width.

The functions of this epithelium are related to the functions of the organ in which it is located (in the ducts - delimiting, in the kidneys osmoregulatory, and other functions). Microvilli are located on the apical surface of cells in the kidney tubules.

Single-layer prismatic (cylindrical) epithelium has a greater cell height compared to width. It lines the mucous membrane of the stomach, intestines, uterus, oviducts, collecting ducts of the kidneys, excretory ducts of the liver and pancreas. Develops mainly from the endoderm. The oval nuclei are shifted to the basal pole and are located at the same height from the basement membrane. In addition to the delimiting function, this epithelium performs specific functions inherent in a particular organ. For example, the columnar epithelium of the gastric mucosa produces mucus and is called mucous epithelium, the intestinal epithelium is called edged, since at the apical end it has villi in the form of a border, which increase the area of parietal digestion and absorption of nutrients. Each epithelial cell has more than 1000 microvilli. They can only be examined with an electron microscope. Microvilli increase the absorption surface of the cell up to 30 times.

IN epithelia, lining the intestines are goblet cells. These are single-celled glands that produce mucus, which protects the epithelium from the effects of mechanical and chemical factors and promotes better movement of food masses.

Single-layer multirow ciliated epithelium lines the airways of the respiratory organs: the nasal cavity, larynx, trachea, bronchi, as well as some parts of the reproductive system of animals (vas deferens in males, oviducts in females). The epithelium of the airways develops from the endoderm, the epithelium of the reproductive organs from the mesoderm. Single-layer multirow epithelium consists of four types of cells: long ciliated (ciliated), short (basal), intercalated and goblet. Only ciliated (ciliated) and goblet cells reach the free surface, and basal and intercalary cells do not reach the upper edge, although together with others they lie on the basement membrane. Intercalary cells differentiate during growth and become ciliated (ciliated) and goblet-shaped. The nuclei of different types of cells lie at different heights, in the form of several rows, which is why the epithelium is called multirow (pseudo-stratified).

Goblet cells are single-celled glands that secrete mucus that covers the epithelium. This promotes the adhesion of harmful particles, microorganisms, and viruses that enter with the inhaled air.

Ciliated cells on their surface they have up to 300 cilia (thin outgrowths of the cytoplasm with microtubules inside). The cilia are in constant motion, due to which, along with mucus, dust particles trapped in the air are removed from the respiratory tract. In the genitals, the flickering of cilia promotes the advancement of germ cells. Consequently, the ciliated epithelium, in addition to its delimiting function, performs transport and protective functions.

II. Stratified epithelia

1. Stratified non-keratinizing epithelium covers the surface of the cornea of the eye, oral cavity, esophagus, vagina, caudal part of the rectum. This epithelium comes from the ectoderm. It has 3 layers: basal, spinous and flat (superficial). The cells of the basal layer are cylindrical in shape. Oval nuclei are located at the basal pole of the cell. Basal cells divide mitotically, replacing dying cells of the surface layer. Thus, these cells are cambial. With the help of hemidesmosomes, basal cells are attached to the basement membrane.

The cells of the basal layer divide and, moving upward, lose contact with the basement membrane, differentiate and become part of the spinous layer. Layer spinosum formed by several layers of cells of irregular polygonal shape with small processes in the form of spines, which, with the help of desmosomes, firmly connect the cells to each other. Tissue fluid with nutrients circulates through the gaps between the cells. Thin filaments-tonofibrils are well developed in the cytoplasm of spinous cells. Each tonofibril contains thinner filaments-microfibrils. They are built from the protein keratin. Tonofibrils, attached to desmosomes, perform a supporting function.

The cells of this layer have not lost mitotic activity, but their division is less intense than that of the cells of the basal layer. The upper cells of the spinous layer gradually flatten and move into the superficial flat layer 2-3 rows of cells thick. The cells of the flat layer seem to spread out over the surface of the epithelium. Their kernels also become flat. Cells lose their ability to undergo mitosis and take the form of plates and then scales. The connections between them weaken and they fall off the surface of the epithelium.

2. Stratified squamous keratinizing epithelium develops from the ectoderm and forms the epidermis, covering the surface of the skin.

The epithelium of hairless skin has 5 layers: basal, spinous, granular, shiny and horny.

In the skin with hair, only three layers are well developed - basal spinous and horny.

The basal layer consists of a single row of prismatic cells, most of which are called keratinocytes. There are other cells - melanocytes and non-pigmented Langerhans cells, which are skin macrophages. Keratinocytes participate in the synthesis of fibrous proteins (keratins), polysaccharides, and lipids. The cells contain tonofibrils and grains of the melanin pigment that come from melanocytes. Keratinocytes have high mitotic activity. After mitosis, some of the daughter cells move to the superior spinous layer, while others remain in reserve in the basal layer.

The main significance of keratinocytes- formation of a dense, protective, non-living horny substance of keratin.

Melanocytes stitched shape. Their cell bodies are located in the basal layer, and processes can reach other layers of the epithelial layer.

Main function of melanocytes- education melanosomes containing skin pigment - melanin. Melanosomes enter neighboring epithelial cells along the processes of the melanocyte. Skin pigment protects the body from excessive ultraviolet radiation. Participating in the synthesis of melanin are: ribosomes, granular endoplasmic reticulum, and Golgi apparatus.

Melanin in the form of dense granules is located in the melanosome between the protein membranes that cover the melanosomes and on the outside. Thus, melanosomes are chemically melanoprodeids. Cells of the spinous layer multifaceted, have uneven boundaries due to cytoplasmic projections (spines), with the help of which they are connected to each other. The stratum spinosum is 4-8 layers of cells wide. In these cells, tonofibrils are formed, which end in desmosomes and firmly connect the cells to each other, forming a supporting-protective frame. The spinous cells retain the ability to reproduce, which is why the basal and spinous layers are collectively called the germinal layer.

Granular layer consists of 2-4 rows of flat-shaped cells with a reduced number of organelles. The tonofibrils are impregnated with keratohealin substance and turned into grains. Keratinocytes of the granular layer are the precursors of the next layer - brilliant.

Shiny layer consists of 1-2 rows of dying cells. In this case, the keratogealin grains merge. Organelles degrade, nuclei disintegrate. Keratohealin transforms into eleidin, which refracts light strongly, giving the layer its name.

The most superficial stratum corneum consists of horny scales arranged in many rows. The scales are filled with the horny substance keratin. On skin covered with hair, the stratum corneum is thin (2-3 rows of cells).

So, the keratinocytes of the surface layer turn into a dense non-living substance - keratin (keratos - horn). It protects underlying living cells from strong mechanical stress and drying out.

The stratum corneum serves as the primary protective barrier, impermeable to microorganisms. The specialization of the cell is expressed in its keratinization and transformation into a horny scale containing chemically stable proteins and lipids. The stratum corneum has poor thermal conductivity and prevents the penetration of water from the outside and its loss by the body. During the process of histogenesis, sweat - hair follicles, sweat, sebaceous and mammary glands are formed from epidermal cells.

Transitional epithelium- originates from mesoderm. It lines the internal surfaces of the renal pelvis, ureters, bladder and urethra, i.e. organs that are subject to significant stretching when filled with urine. The transitional epithelium consists of 3 layers: basal, intermediate and superficial.

The cells of the basal layer are small cubic, have high mitotic activity and perform the function of cambial cells.

Genetic classification of epithelia (examples)

Epithelia of the skin type (ectodermal) Multilayered squamous keratinizing and non-keratinizing epithelium.; epithelium of salivary, sebaceous, mammary and sweat glands; transitional epithelium of the urethra; multirow ciliated epithelium of the airways; alveolar epithelium of the lungs; epithelium of the thyroid and parathyroid glands, thymus and adenohypophysis.
Epithelia of intestinal type (enterodermal) Single-layer prismatic epithelium of the intestinal tract; epithelium of the liver and pancreas.
Renal type epithelium (nephrodermal) Nephron epithelium.
Coelomic epithelium (coelodermal) Single-layer squamous epithelium of the serous integuments (peritoneum, pleura, pericardial sac); epithelium of the gonads; epithelium of the adrenal cortex.
Neuroglial epithelium Epindymal epithelium of the cerebral ventricles; meningeal epithelium; retinal pigment epithelium; olfactory epithelium; glial epithelium of the hearing organ; taste epithelium; epithelium of the anterior chamber of the eye; chromophobe epithelium of the adrenal medulla; perineural epithelium.

Topography, sources of development, structure, regeneration.

Single layer epithelia

The sources of embryonic development of epithelia are the ectoderm, endoderm, intermediate and lateral (splanchnotome) parts of the mesoderm, as well as mesenchyme (endothelium of blood vessels, heart chambers). Development begins from 3-4 weeks of embryonic development. Epithelia do not have a single source of origin.

The endothelium develops from mesenchyme. Single-layer squamous epithelium of the serous integument - from splanchnotomes (ventral part of the mechoderm).

Morphological classification

All cells of single-layer epithelium are located on the basement membrane. Single layer flat epithelium (vascular and cardiac endothelium and mesothelium)

Single layer cubic epithelium (lining the proximal and distal parts of the renal tubules, has a brush border and basal striations)
Single layer prismatic(columnar) epithelium
- Limitless (gallbladder)
- Limb (small intestine)
- Glandular (stomach)
Multi-row (pseudo-multilayer) epithelium
- Ciliated or ciliated (airways)

The structure of various types of single-layer epithelium

Single layer squamous epithelium formed by flattened cells with some thickening in the area where the discoid nucleus is located. These cells are characterized by diplomatic differentiation of the cytoplasm: it is divided into the inner part (endoplasm), which is located around the nucleus and contains most of the relatively few organelles, and the outer part (ectoplasm), which is relatively free from organelles. Examples of such epithelium are the linings of blood vessels - endothelium, body cavities - mesothelium(part of the serous membranes), some renal tubules ( thin part loops of Henle), lung alveoli(type I cells).

Single layer cuboidal epithelium formed by cells containing a spherical nucleus and a set of organelles that are better developed than in squamous epithelial cells. This epithelium is found in renal tubules, V thyroid follicles, V small pancreatic ducts, bile ducts of the liver, small collecting ducts of the kidney.

Single-layer prismatic (cylindrical or columnar) epithelium formed by cells with pronounced polarity. The ellipsoidal nucleus lies along the long axis of the cells and is usually somewhat shifted to their basal part, and well-developed organelles are unevenly distributed throughout the cytoplasm. This epithelium covers the surface stomach, guts, forms a lining large pancreatic ducts, large bile ducts, gallbladder, fallopian tube, wall large collecting ducts of the kidney. In the intestine and gall bladder this epithelium bordered.

Single-layer multirow (pseudostratified) prismatic epithelium formed by cells of several types having different sizes. In these cells, the nuclei are located at different levels, which creates a false impression of multilayering (determining the second name of the epithelium).

Single-layer multi-row prismatic ciliated (ciliated) epithelium airways- the most typical representative of multirow epithelia. It also lines the cavity of the fallopian tubes.

Single layer double row prismatic epithelium found in the epididymal duct, vas deferens, end parts of the prostate gland, seminal vesicles.

Localization of single-layer epithelium in the body

1) Mesothelium – covers the serous membranes: pleura, epi-, pericardium, peritoneum

2) Endothelium – lines the inside walls of the heart, blood vessels, lymphatic vessels

3) the epithelium of some renal tubules, the outer leaf of the renal tubule capsule, etc.

Stratified epithelia

Sources of development

Localization in the body

Stratified squamous epithelium is the most common type of epithelium in the body.

Stratified squamous keratinizing epithelium

Epidermis skin
Some areas oral mucosa

Stratified squamous non-keratinizing epithelium

Cornea eyes
Conjunctiva
Mucous membranes of the pharynx, esophagus, vagina, vaginal part of the cervix, part of the urethra, oral cavity

Stratified cuboidal epithelium is rare in the human body. It is similar in structure to stratified squamous epithelium, but the cells of the surface layer have a cubic shape.

Wall of large ovarian follicles
Sweat ducts And sebaceous glands skin.

Stratified prismatic epithelium is also rare.

Some areas of the urethra
Large excretory ducts of the salivary and mammary glands(partially)
Zones sharp transition between multilayer flat And single-layer multi-row epithelium

Transitional epithelium

Most of urinary tract

Structure, cellular composition of layers

Multilayer flat keratinizing epithelium is the epithelium of the skin. Develops from the ectoderm. Layers:

Basal layer- in many ways similar to a similar layer of stratified non-keratinizing epithelium; additionally: contains up to 10% melanocytes - process cells with inclusions of melanin in the cytoplasm - provide protection from UV rays; there is a small quantity Merkel cells (part of mechanoreceptors); dendritic cells with a protective function by phagocytosis; V epithelial cells contains tonofibrils (special purpose organelle - provides strength).
Layer spinosum- from epithelial cells with spiny projections; meet dendrocytes And lymphocytes blood; epithelial cells are still dividing.
Granular layer- from several rows elongated flattened oval cells with basophilic granules of keratohyalin (the precursor of the horny substance - keratin) in the cytoplasm; cells don't divide.
Shiny layer— cells are completely filled with elaidin (formed from keratin and tonofibril breakdown products), which reflects and strongly refracts light; Under a microscope, the boundaries of cells and nuclei are not visible.
Layer of horny scales (stratum corneum)- comprises horny plates made of keratin containing bubbles with fat and air, keratosomes (corresponding to lysosomes). The scales peel off from the surface.

Multilayer flat non-keratinizing epithelium. Layers:

Basal layer — cylindrical epithelial cells with weakly basophilic cytoplasm, often with a mitotic figure; in small quantities stem cells for regeneration;
Layer spinosum- consists of a significant number of layers spinous cells , cells actively share.
Cover cells — flat, senescent cells, don't share, gradually peel off from the surface.

Transition epithelium. Layers:

Basal layer- from small dark low-prismatic or cubic cells - poorly differentiated and stem cells , provide regeneration;
Intermediate layer- from large pyriform cells , narrow basal part, in contact with the basement membrane (the wall is not stretched, so the epithelium is thickened); when the wall of the organ is stretched, the pyriform cells decrease in height and are located among the basal cells.
Cover cells — large dome-shaped cells ; when the organ wall is stretched, the cells flatten; cells don't share, gradually peel off.