Nephron is a structural unit of the kidney, responsible for the formation of urine. Working 24 hours, the organs pass up to 1700 liters of plasma, forming a little more than a liter of urine.
Nephron
The work of the nephron, which is the structural and functional unit of the kidney, depends on how well the balance is maintained, the waste products are taken out. Overnight, two million kidney nephrons, as much as they are in the body, produce 170 liters of primary urine, thicken to a daily amount of up to one and a half liters. The total area of the excretory surface of nephrons is almost 8 m2, which is 3 times the area of the skin.
The excretory system has a high safety reserve. It is created due to the fact that only one third of the nephrons work simultaneously, which allows you to survive when the kidney is removed.
Structure
Kidney nephron departments are as follows:
- Begins in the cortical layer of the kidney by the Bowman capsule, which is located above the glomerulus of the capillaries of the arterioles.
- The capsule of the kidney of the kidney communicates with the proximal( proximal) canal, directed to the brain substance - this is the answer to the question in which part of the kidney the capsules of nephrons are.
- The canal passes into the loop of Henle - first to the proximal segment, then - the distal one.
- The end of the nephron is considered to be the place where the collecting tube begins, where secondary urine enters from a multitude of nephrons.
Capsule
Cells of podocytes, surround the glomerulus of capillaries in the likeness of caps. Education is called a kidney body. In its pores penetrates the fluid, which is in the space Bowman. Here the infiltrate is collected - the product of the filtration of the blood plasma.
Proximal tubule
This species consists of cells covered from the outside with a basal membrane. The inner part of the epithelium is provided with outgrowths - microvilli, like a brush, lining the tubule along the entire length.
Outside, there is a basal membrane, collected in numerous folds, which when filling the tubules straighten. In this case, the tubule acquires a rounded shape in diameter, and the epithelium flattenes. In the absence of fluid, the diameter of the tubule becomes narrow, the cells acquire a prismatic appearance.
Features include reabsorption:
- H2O;
- Na - 85%;
- of Ca, Mg, K, Cl ions;
- salts - phosphates, sulphates, bicarbonate;
- compounds - proteins, creatinine, vitamins, glucose.
From the tubule, reabsorbents enter the blood vessels, which are dense with the canalic network. In this area, bile acid is absorbed into the cavity of the tubule, oxalic, paraaminohippuric, uric acids are absorbed, adrenaline, acetylcholine, thiamine, histamine are absorbed, drugs such as penicillin, furosemide, atropine, etc. are transported.
Henle
loop After entering the brain, the proximalThe canaliculus passes into the initial section of the loop of Henle. The canal passes into the descending section of the loop, which descends into the brain substance. Then the ascending part rises to the cortical substance, approaching the Bowman capsule.
The internal structure of the loop first does not differ from the structure of the proximal tubule. Then the lumen of the loop narrows, through it passes the filtration of Na into the interstitial fluid, which becomes hypertonic. This is important for the operation of collecting tubes: due to the high concentration of salt in the washer fluid, they absorb water. The ascending section widens into a distal tubule.
Distal canalicle
This region already, in short, consists of low epithelial cells. There are no nads inside the canal, the basal membrane folding is well expressed on the outside. Here there is a reabsorption of sodium, reabsorption of water continues, secretion into the lumen of the tubule of hydrogen ions, ammonia.
On the video scheme of the structure of the kidney and nephron:
Types of nephrons
By the features of the structure, the functional purpose distinguishes such types of nephrons that function in the kidney:
- cortical - super-formal, intracortical;
- are juxtamendullar.
Cortical
In the cortical layer are two types of nephrons. Super-official make up about 1% of the total number of nephrons. They differ in the surface location of the glomeruli in the cortex, the shortest loop of Henle, a small amount of filtration.
The number of intracortical - more than 80% of nephrons of the kidney, located in the middle of the cortical layer, play a major role in the filtration of urine. Blood in the glomerulus of the intraocortical nephron passes under pressure, as the resulting arteriol is much wider than the outgoing.
Yukstadullary
Yukstamedullary is a small part of the nephron of the kidney. Their number does not exceed 20% of the number of nephrons. The capsule is located on the border of the cortical and cerebral layer, the rest of it is located in the cerebral layer, the loop of Henle descends almost to the most renal pelvis.
This type of nephron is of decisive importance in the ability to concentrate urine. The peculiarity of the juxtamedullary nephron is that the excretory artery of this type of nephron has the same diameter as the bearer, and the Henle loop is the longest of all.
Vesting arterioles form loops that move into the medulla in parallel to the Henle loop, flow into the venous network.
Functions
The kidney nephron function includes:
- urine concentration;
- regulation of vascular tone;
- control of blood pressure.
Urine is formed in several stages:
- in the glomeruli the blood plasma is filtered through the arterioles, primary urine is formed;
- reabsorption from the filtrate of nutrients;
- urine concentration.
Cortical nephrons
The main function is the formation of urine, the reabsorption of useful compounds, proteins, amino acids, glucose, hormones, minerals. Cortical nephrons participate in the processes of filtration, reabsorption due to the peculiarities of the blood supply, and reabsorbed compounds immediately enter the blood through the closely located capillary network of the outgoing arterioles.
Yuqstadullary nephrons
The main work of the juxtamidullary nephron is to concentrate the urine, which is possible due to the peculiarities of the blood flow in the outgoing arterioles. Arteriola does not pass into the capillary network, but passes into the venules that flow into the veins.
Dysfunction of the nephron and how to restore
The failure of the nephron leads to changes that affect all body systems.
Disturbances caused by nephron dysfunction include disorders:
- acidity;
- water-salt balance;
- metabolism.
Diseases that are caused by a violation of nephron transport functions are called tubulopathies, among which are:
- primary tubulopathies - congenital dysfunctions;
- secondary - acquired disturbances of the transport function.
The causes of secondary tubulopathy are nephron damage caused by toxins, including drugs, malignant tumors, heavy metals, myeloma.
At the site of localization of tubulopathy:
- proximal - damage to proximal tubules;
- distal - damage to the functions of the distal convoluted tubules.
Proximal tubulopathy
Damage to the proximal areas of the nephron leads to the formation of:
- phosphaturia;
- hyperaminoaciduria;
- renal acidosis;
- glucosuria.
The disruption of phosphate reabsorption leads to the development of a rickets-like bone structure, a condition that is resistant to vitamin D treatment. Pathology is associated with the lack of a phosphate carrier protein, a lack of receptors binding calcitriol.
Renal glucosuria is associated with a decrease in the ability to absorb glucose. Hyperaminoaciduria is a phenomenon in which the transport function of amino acids in the tubules is disrupted. Depending on the type of amino acid, pathology leads to various systemic diseases.
So, if the reabsorption of cystine is disrupted, the disease cystinuria develops - an autosomal recessive disease. The disease manifests itself as a lag in development, with renal colic. In urine with cystinuria, the appearance of cystine stones, which easily dissolve in an alkaline environment.
Distal tubulopathy
Pathologies of the distal sections are manifested by renal water diabetes, pseudohyperdosteronism, tubular acidosis. Renal diabetes - hereditary damage. The congenital disorder is caused by the lack of reaction of the cells of the distal tubules to the antidiuretic hormone. The lack of reaction leads to a violation of the ability to concentrate urine. The patient develops polyuria, up to 30 liters of urine can be released per day.
Combined disorders develop complex pathologies, one of which is called de Toni-Debreu-Fanconi syndrome. At the same time, the reabsorption of phosphates, bicarbonates is violated, amino acids, glucose are not absorbed. The syndrome is manifested by delayed development, osteoporosis, pathology of the structure of bones, acidosis.