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Mechanism Of Concentration Of The Filtrate

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Animals build up ions like Na+ and K+ as well as urea, ammonia, also uric acid, water and CO2, Cl-, phosphate, sulphate, and other substances, either through metabolic activities or another method, such as excessive eating. These chemicals have to be entirely or partially removed. This chapter will teach you the processes for the removal of these chemicals, with a focus on typical wastes containing nitrogen. The main culprits are urea, uric acid, and ammonia. types of nitrogenous wastes that animals emit. Ammonia is the most harmful type and needs a lot of water to be eliminated, the least poisonous substance, uric acid, can be eliminated with the least amount of water evaporation.

Urine Formation

The three basic processes that go into producing urine—glomerular filtration, reabsorption, and secretion—occur in various regions of the nephron. The purification of the bloodstream, which would be carried out as the initial stage in the generation of urine, is known as glomerular filtration and occurs by the glomerulus. On the whole, The kidneys filter 1100–1200 cc of blood each minute, which makes about approximately 1/5 of the blood would be pumped out by the heart ventricle in a minute. Blood is filtered by the blood pressure in the capillary of the glomerulus. the blood vessels of the glomerulus, endothelium would consist of three layers, the foundation membrane separating the Bowman’s capsule’s epithelium from these dual layers. Bowman’s capsule’s podocytes, which are epithelial cells, are structured in a complex way to leave certain tiny openings known as filters apertures or pores of the slit. Through this, blood is purified so thoroughly. Practically all of the components of the plasma, with the exception of the membranes Proteins transfer to the Bowman’s capsule’s lumen. Consequently, it is believed to be an ultrafiltration process. The volume of kidney filtrate produced each minute is measured as the rate of glomerular filtration (GFR). In a healthy person, GFR is about 125 ml each minute, or 180 litres per day! The kidneys have internal systems for controlling the glomerular filtration rate, and rate of filtration. Juxta employs an effective mechanism of this nature. Juxtaglomerular system (JGA). JGA, a unique sensitive area, is created at the point where the afferent arteriole and distal convoluted tubule come into touch by cellular changes. The JG can be activated by a drop in GFR. renin, which can increase glomerular blood flow, from cells. The GFR returns to normal as a result. A contrast of the daily filtrate production (180 litres) along with the amount of urine excreted (1. 5 litres per day) indicate that approximately 99% of The renal tubules must reabsorb per cent of the filtrate. This Reabsorption is the process name. Different tubular epithelial cells Segments of the nephron either actively or passively carry out this function. For instance, in the filtrate, molecules like carbohydrates, acids of amine, Na+, etc., are aggressively reabsorbed in contrast to the nitrogenous wastes, which are absorbed by passive movement Water is also passively reabsorbed in the early sections of the kidney. The tubular cells produce chemicals like H+ during the production of urine, Potassium enters the filtrate, along with ammonia. Another crucial process is tubular secretion. phase in the production of urine because it aids in the preservation of ions and acids and basic fluid balance in the body.

Nephron Structure


Mechanism of concentration of Filtrate 

Animals like mammals can create concentrated urine. The vasa recta and Henle’s loop are important in this. Henle’s loop would consist of the two limbs which would have opposing directions of filtrate flow, forming an opposite current. Blood likewise moves in a counter-current rhythm through the two vasa recta limbs. The closeness of the Henle’s loop The vasa recta, along with the countercurrent in them, assist in keeping a rising osmolarity in the direction of the interstitium of the medullary inner layer or from 300 and 1200 m OsmolL-1, with the cortex being the highest. medulla. NaCl and urea are the principal contributors to this gradient.

The loop of Henle would have an ascending limb which would be switched for the descending limb of the vasa recta, which transports NaCl. The interstitium receives back NaCl. via the vasa recta’s rising section. Likewise, trace levels of urea enter the narrow limb of Henle’s loop’s ascending portion, which The collecting tubule carries the substance back to the interstitium. the earlier described the particular arrangement’s facilitation of drug movement. the countercurrent mechanism, which consists of Henle’s loop and vasa recta.  interstitium of the medullary would be having a concentration gradient which is preserved because of this process. Such an interstitial gradient is beneficial. allowing water to flow from the collecting tubule easily as a result the filtrate is concentrated (urine). The ability of human kidneys to create virtually. excretory system of Humans would use the countercurrent multiplier, also referred to as the countercurrent mechanism, to concentrate filtrate in the kidneys. The production of concentrated urine involves the nephrons, the kidney’s functional unit. The vasa recta travel along with the concentration process from the kidney cortex to the medulla. The filtrate enters a loop of Henle of two limbs in opposing directions, and cells of blood would flow through the vasa recta follows suit. 

The following techniques are used to create concentrated urine:

  • NaCl is transported from the loop of Henle’s ascending limb to the vasa recta f descending limb. The tissue that lies between the vasa recta and the Henle loop is known as interstitium. So, a concentrations pressure difference is created that extends from the cortex to the medulla at a distance of 300 mm. The unit of osmolarity known as milliosmoles (mOsm) is used to measure the concentration of osmosis active substances.
  • The Loop of Henle’s descending limb carries urea to the interstitium, aiding in this process.
  • Urine encounters progressively higher solute concentrations in the interstitium as it descends in the collecting tubule. As a result, osmosis continues to cause it to lose water.

Multiplication of counter-currents

Your kidneys have a special process for water reabsorption from the fluid of the tubule called countercurrent multiplication. When you use energy to establish an osmotic gradient in the kidneys, you can recover water from the kidney tubules and create a concentrated solution. This process is known as countercurrent multiplication. You don’t need to drink continuously to stay hydrated because this mechanism prevents you from producing endless amounts of dilute urine each day.

Recycling of Urea

The anti-diuretic increases the water penetration but not urea permeability in the cortex and outside collecting ducts of the medulla leading ammonia to concentration in the kidney tubules. This increases the osmotic gradient and aids in water absorption. The osmotic gradient produced by the Henle loops is also influenced by the recycling of urea in the inner medulla

Conceptual Questions 

Question 1: Our urine is either concentrated or diluted. A unique mechanism makes this possible. What mechanism is it?


Counter current mechanism which would take place in the  Henle’s Loop the medullary interstitium would have the concentration gradient which would be maintained by a countercurrent process. The interstitial gradient’s presence makes it easier for water to exit the collecting tubule, which concentrates the filtrate (urine).

Question 2: Which act as the principal contributors in the vasa recta?


NaCl and urea act as the principal contributors.

Question 3: Which would be the most harmful excretory product?


Ammonia is the most harmful product and should be eliminated.

Question 4: Which would be least harmful?


Uric acid would be the least harmful product.

Question 5: Which are called ammonotelic?


Organisms which would excrete ammonia are called ammonotelic.

Question 6: Which are called uricotelic?


Organisms which would excrete uric acid are called uricotelic.

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Last Updated : 28 Nov, 2022
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