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Counter-current multiplication which occurs on the Vasa Recta helps maintain high osmolarity in the renal medulla

Sodium Chloride (NaCl, or salt) is pumped out of the ascending limb of the loop of Henle. The result is that the renal medulla has a high salt concentration, and therefore a low water concentration.

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Q: How is the high osmolarity of the renal medulla is maintained?
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What is high plasma osmolality?

This is when you have a high concentration of solute (ie. Na) in your blood in contrast to a low concentration of water in the blood.


What is osmolarity?

Osmolarity is a measure of the osmoles of solute per liter of solution.


What is the main factor that creates the high osmotic gradient between the cortex and medulla?

A high osmotic gradient between the cortex and the medulla is caused by the running, walking, or jumping of a human person. These simple actions cause the osmotic gradient to rise significantly.


What effects would increased blood pressure have on nephron function?

Hypertension represents a common and powerful predisposing factor for cardiovascular disease or events and renal failure. Approximately 90% of patients with end-stage renal disease (ESRD) have a history of hypertension. High blood pressure may initiate renal damage and also increase the rate of progression of renal insufficiency. Persistent high blood pressure represents the early trigger mechanism for renal disease. The final pathway is represented by progressive sclerosis of glomeruli (Vascular part of nephron). A main role is played by transforming growth factor 1 (TGF1), a multifunctional cytokine that regulates cell growth, differentiation, matrix production, blocks matrix degradation, inducing fibrosis in many tissues, including kidney, blood vessels, lung and heart. High circulating levels of TGF1 can mediate renal fibrosis and loss of function.


What is the treatment for renal parenchymal disease?

The treatment for renal parenchymal disease can include dialysis and kidney transplant in severe cases. If the disease is not in an advanced stage, then the main goal of treatment is to restrict the intake of salt or potassium and address symptoms like high blood pressure through diet and different medications. This disease causes scarring of the kidneys and can result in kidney failure.

Related questions

Does water flow from Low Osmolarity to High Osmolarity?

yes, water flows from low osmolarity to high osmolarity when two solutiona are separated by a semi-permeable membrane till the solutions on either side of the membrane attains equal osmolarity.


What is high plasma osmolality?

This is when you have a high concentration of solute (ie. Na) in your blood in contrast to a low concentration of water in the blood.


What happens when the loop of henle is permeable to sodium and water along both segments?

Mixed answer. The descending limb of the Nephron Loop (loop of henle) is not permiable to sodium. It is permiable to Urea that diffuses from the permiable lower end of the collecting tubule(CT). All a part of keeping the osmolity of the renal medulla high.


What is osmolarity?

Osmolarity is a measure of the osmoles of solute per liter of solution.


How does acidosis cause hyperglycemia?

Acidosis is usually caused by increased carbon dioxide in the body leads to increase concentration of carbonic acid. The prolonged acidosis may lead to renal diseases due to high concentration of carbonic acid. So adrenaline secretion becomes high from adrenal medulla and as adrenaline is hypoglycemic hormone, it leads to hyperglycemia.


State 2 causes of renal failure?

Most cases of renal failure can be attributed to high blood pressure and diabetes. There are other conditions which can cause renal failure, but it isn't common.


In what way does the composition of the blood in the renal artery differ from the renal vein?

The renal artery takes blood to the kidney. The renal vein takes blood away from the kidney. In the kidney, the waste product urea is filtered out of the blood. So the main difference is in the amount of urea in the blood: high in the renal artery and low in the renal vein.


Describe how the osmotic pressure gradient in renal medulla is formed and the role of osmotic pressure gradient in concentration and dilution of urine?

The osmotic pressure of renal medulla is produced most trough a balance between water and Na+/K+/Cl-/urea+ entering it. First, water enters the medulla going out from the descending limb of Henle's loop and out from the medullar collector ducts. Remember that for water to cross the nephron tubules it is strictly necessary that the tubule cells express the protein aquaporin, i.e., a water channel in all features similar to ion-channels1. A similar channel called UT (for urea transporter) enables that urea cross the tubules wall. Well, aquaporin is constitutively expressed in renal medulla along the descending limb and at the collector ducts. The UT is expressed in medulla at the turn of Henle's loop and at the collector ducts. Both the transporters at the collector ducts are presented at the apical surfaces (inside the tubule) only if the hormone ADH2 is present. Ion channels are highly expressed3 mainly at ascending limb of Henle's loop. A similar membrane structure is present at the vasa recta, i.e., the capillaries that follow the Henle's loop going into the renal medulla and back to the renal cortex. These vessels are permeable too much more permeable to ions than to H2O, and are not permeable to urea and proteins. So, they keep the same osmolarity of the medulla trough ion exchange than trough water exchange. The osmotic gradient in the medulla is created because a lot of water enters the medulla at its highest parts, due to osmosis, coming from the descending limb of Henle's loop (~25% of renal flow4). Ions are also released at the highest parts of the ascending limbs, because of Na+/K+/2Cl- ATPases5 mediating active transport from the tubules to the intercellular fluid of medulla. The balance between ions and H2O being released into medulla creates a hyper-osmotic fluid. The urea going out of the collector ducts increases further this osmolarity, because urine has much more urea than the renal medulla (1000 mM in urine vs. 500 mM in medulla). The release of this hyper-osmotic fluid into the medulla is the strongest regulator of the H2O re-absorption in the kidney. The reason by which this osmolarity does not increase unlimited is because the vasa recta are continuously washing it out. The blood that passes trough the vasa recta increases in volume, because it receives ions and water, keeping its osmolarity. While the Na+/K+/2Cl- ATPases acts as a motor pumping the medulla to higher osmolarities, the water crossing the descending limb of Henle's loop passively decreases it. Because of the water re-absorption at the collector ducts are low, it does not interfere too much with the medulla's osmotic pressure. So, despite the medulla's osmotic gradient is too much necessary for renal re-absorption of water, it is of little control by mechanisms which regulate urine production. The 2nd major site of water re-absorption in the kidney is however at the distal convoluted tube, at the cortex. About 5% of renal flow of water is re-absorbed there, and it can be altered a lot due to the presence of aquaporin in membranes, strictly under the control of ADH. Because the tubules fluid there is iso-osmotic to the cortex (290 mOs), the water transport occurs driven by the active transport of Na+ out from the tubular fluid6. When ADH levels are low in the blood (possibly due to decreased blood osmolarity or drugs like caffeine and alcohol), too little aquaporin is present at the inner of the distal convoluted tubule, and the transport of Na+ is not followed by water transport. A lot of water remains into the tubule, being excreted as a hypo-osmotic urine reaching even 20 mL/min or 8 L/day. Conversely, if ADH levels are high in the blood (possibly due to increased blood osmolarity), a lot of aquaporin is present at the inner of the distal convoluted tube, enabling water to follows the Na+ active transport. Then, urine acquires a hyper-osmotic character as it crosses the medulla in a low-flux faction, decreasing to about 0.4 ml/min or 500 mL/day. ---- 1Each cell is rounded by a lipid membrane, which does not allow polar molecules to pass because they do not dissolve in it. Substances such as H2O, Na+ (sodium), K+ (potassium), Cl- (chloride) and urea are highly polar, so they cannot pass the cell membranes unless transmembrane proteins create a channel. These proteins form pores too specific, however, allowing only one of H2O, Na+, K+ or urea to pass trough it. There are water-channels (aquaporin), sodium-channels, potassium-channels and urea transporters (not exactly a channel). 2 ADH means Anti-Diuretic Hormone, or vasopressin. It is a protein released by the pituitary gland into the blood when specific neurons detect a slight increase in blood osmolarity, which is kept at 290 mOs. 3 A cell expresses a protein when the cell activates the gene codifying it. Although all cells of the body have the sane genetic code, not all genes are activated at the same cell-type and at the same time. In fact, about only 1% of the genes in human genome is expressed in any cell. There are constitutive genes, which remain activated in a tissue despite any regulation. Other genes are expressed only under specific environmental stimulation, usually due to hormones reaching the cell. 4About 1100 mL/min of blood passes trough kidney (650 mL/min of plasma), of which 120 mL/min enters the renal filtration system, pumped by a pressure gradient of 20 mmHg lower into the Bowman's capsule than in the blood vessels. The non-filtered part goes to the vasa recta and recovers most of it constituents, but a part of its urea and water. 5 Na+/K+/2Cl- ATPases are membrane proteins expressed at the end of the ascending limb of Henle's loop. This region of the loop does not express aquaporin and UT, so it is impermeable to water and urea. The protein hydrolyses intracellular ATP in order to force large amounts of Na+/K+/2Cl- ions out of the tubular fluid and into the tubular cells, from which the ions leave passively, trough ion channels. 6 The active transport here is driven by the classical Na+/K+ ATPase. This protein is present at the outer face of the tubular cells and if forces Na+ ions out of the cells. The fluid Na+ ions enter the cells by passive sodium-channels at the inner face. Similarly, K+ ions enter the cells and the tubular fluid coming from out of the tubules. Because more sodium exits than potassium enters, the Na+/K+ ATPase decreases the osmolarity of the tubular fluid. This does not happen, however, because water can freely cross the tubule walls, following the Na+ ions. The presence of ion channels and Na+/K+ ATPase at this portion of the renal tubules are under the control of the hormone aldosterone.


Damage to the medulla would most likely result in?

it can lead to high blood pressure


Can High blood pressure cause chronic renal failure?

Yes


Contraindication of IVP?

renal failure, high serum creatinine and pregnancy


Can high blood pressure be a symptom of Chronic renal failure?

Yes