Introduction the countercurrent multiplier theory of the. One of the main functions of the kidneys is to keep the solute load of. A detailed explanation of how the loop of henle helps to concentrate urine using the countercurrent multiplication mechanism. The length of the loop is directly related to the concentration of urine and operates as a. This part of the renal tubule is divided into a thin and thick ascending limb. Feb 27, 2019 the human kidney is made up of about a million nephrons, the filtering units of this complex and highly vascular organ. The loop of henle is supplied by blood in a series of straight capillaries descending from the cortical efferent arterioles.
Sodium and chloride ions are actively pumped from the ascending limb of the loop but water is retained, since the ascending limb is impermeable to water. Mar 28, 2018 a stepwise gradient of salts is built inside the medulla tissue by the loop of henle. The countercurrent flowarrangement of henles loop and the vasa recta traps salt and urea within the medulla and minimizes the volume of water entering the medullary interstitium. Learn about how the loop of henle develops a concentration of 1200 mosml in the medulla of the kidney via a mechanism called countercurrent multiplication, or countercurrent exchange. A conceptual model of the countercurrent multiplication mechanism, now so. Countercurrent multiplication in the kidneys is the process of using energy to. Usmle is a joint program of the federation of state medical. Each nephron is composed of a highly coiled tubule, one end of which forms a. Incomplete loop of henle in birds student doctor network. Its primary function is reabsorption of nacl and water. In a countercurrent multiplier, the combined action of active pumping and circulation and recirculation of solutes around the loop of henle create an osmotic gradient with the following properties. This research was supported by usphs program grant. It also excretes waste products, the most notable being urea. Loop of henle and distal nephron flashcards quizlet.
This countercurrent flow or countercurrent multiplier allows concentrated urine to be produced. The countercurrent multiplier system recirculates salt and thus traps some of the salt that enters the loop of henle in the interstitial fluid of the renal medulla. The loop of henle is found in the medulla of the kidney. Mimi lam, professor at case western reserve university school of medicine, explains the countercurrent multiplier. This function allows production of urine that is far more concentrated than blood. Water levels and the kidney scool, the revision website. Countercurrent multiplication in the kidney video khan. The countercurrent mechanism partially contributes to generation of the corticopapillary osmotic gradient and is the product of juxtamedullary nephrons which possess long loops of henle that extend far into the renal medulla.
Through the countercurrent multiplier effect, a hypertonic medulla is created allowing reabsorption of water from the collecting duct and the descending limb via osmosis. Its primary function uses a countercurrent mechanism in the medulla to reabsorb water and ions from the urine. Counter current mechanism concentrated urine formation byjus. The loop of henles main function is to create a concentration gradient in the medulla of the kidney. In the descending limb, only water is reabsorbed into the renal medulla and blood vasa recta. Loop of henle 1002 800 alh 400 402 200 dlh the countercurrent multiplier cortex medulla h 2o 1200 285 100 502 802 1100 1102 500 300 900 800 600 salt. Transport of nacl without water in the thin and thick ascending limb of the loop of henle results in an interstitial osmolal gradient from 285 mosmolkg in the cortex, similar to plasma to 1200 mosmolkg in the medulla at the tip of the renal papilla. Khan academy is a nonprofit with the mission of providing a free. In the descending limb, only water is reabsorbed into the renal medulla and blood vasa.
The three segments of the loops of henle have different characteristics that enable countercurrent multiplication. The loop of henle is found between the proximal convoluted tubule and the distal convoluted tubule in the nephron. Animals in arid climates have very long loops of henle and produce small quantities of highly concentrated urine. Physiological role of the loop of henle in urinary concentration.
The entire process that i have just described is called countercurrent multiplication. The countercurrent multiplier system uses the salt reabsorbed from the ascending limb of the loop of henle to lay down salts there. Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Learning objectives at the end of this lecture, you will be able to. Write what is loop of henle and its function science. In doing this it creates a hypertonic medulla it does this by using a countercurrent multiplier. According to this hypothesis, the ioops of henle serve as a countercurrent multiplier system to generate and maintain a medullary osmotic gradient which increases from the cortex to the tip of the papilla. The thin descending limb is passively permeable to both water and small solutes such as sodium chloride and urea. The principal function of the loop of henle appears to be the recovery of water and sodium chloride from the urine. If youre behind a web filter, please make sure that the domains. The length of the loop is directly related to the concentration of urine and operates as a countercurrent multiplier system. The loop of henle acts as a countercurrent multiplier see figure 355 and as such creates a medullary interstitial osmolar gradient.
Using a classic paper by gottschalk and mylle to teach the. Normal renal function hebrew university of jerusalem. The theory of counter current multiplication states that if the transport processes in the loop of henle could produce a small osmotic gradient at any horizontal level between the descending and ascending limbs, this could be multiplied into a large longitudinal gradient by the counter current arrangement flow in opposite directions in the. Countercurrent multiplication system without active transport. Jul 01, 2008 the loop has a hairpin bend in the renal medulla. Experimental validation of the countercurrent model of urinary.
The ascending limb drains urine into the distal convoluted tubule. Countercurrent mechanisms the mechanisms shown here are traditionally called the countercurrent multiplier and the countercurrent exchanger. Kidney function counter current mechanism animation youtube. The loop of henle generates an osmotic concentration gradient in its adjoining fluid, hereby allowing urine production which is more osmotically concentrated than blood plasma. Urea is produced in the liver and contains the nitrogen derived from amino acids or proteins. Lecture 35 loop of henle countercurrent multiplier. Why is the countercurrent multiplier called like that. Study 45 terms countercurrent exchange system flashcards. Little attention was paid to the loop of henle in smiths book, largely due to the lack of any knowledge of its function, and schematic diagrams of the nephron depicted the loop of henle as if it.
The loop of henle establishes medullary hyperosmolarity the ascending limb of the loop of henle transports solutes nacl out of the tubule lumen with little or no water, generating an hyperosmotic medullary interstitium and delivering an hyposmotic tubule fluid to the distal tubule. Reabsorption and secretion along the loop of henle anatomy. The mechanism that the kidneys use to concentrate urine is called the. These nephrons perform the major function of the kidney, which is to clear harmful substances from the body by filtering the blood. Information and translations of loop of henle in the most comprehensive dictionary definitions resource on the web. In order for urea to function in this role each of the tubu. Demystifying the countercurrent multiplier youtube. The fluid is increasingly concentrated as it moves down and increasingly dilute as it moves up. The mechanisms shown here are traditionally called the countercurrent multiplier and the countercurrent exchanger. In a countercurrent multiplier, the combined action of active pumping and circulation and recirculation of solutes around the loop of henle create an. This system results in a gradually increasing concentration of renal interstitial fluid from the cortex to the inner medulla.
Countercurrent multiplication in the loop of henle youtube. Initially the countercurrent exchange mechanism and its properties were proposed in 1951 by professor werner kuhn and two of his former students who called the mechanism found in the loop of henle in mammalian kidneys a countercurrent multiplier and confirmed by laboratory findings in 1958 by professor carl w. Loop of henle definition of loop of henle by medical dictionary. The loop is an important part of the whole system, as it. Terms in this set 9 the countercurrent arrangement of the two limbs of the loop of henle becomes a multiplier of electrolyte concentration due to which other characteristic. Describe the counter current multiplier system in the loop of. To do this, it uses a countercurrent multiplier mechanism in the medulla. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. The other part of the solution, and the reason that the loop of henle is in fact a loop lies in the principle of countercurrent multiplication. Sodium and chloride ions are actively pumped from the ascending limb of the loop but water is retained, since the ascending limb is impermeable. Osmosis is a challenging topic for students with many students holding misconceptions about the process 1. Describe the counter current multiplier system in the loop.
The mechanism of action increases the excretion of sodium, water, chloride, magnesium, potassium, and bicarbonate, thereby promoting diuresis skidmoreroth, 2008. Apr 07, 2016 learn about how the loop of henle develops a concentration of 1200 mosml in the medulla of the kidney via a mechanism called countercurrent multiplication, or countercurrent exchange. Jul 31, 2009 the counter current multiplier system. In the presence of antidiuretic hormone adh, the isosmotic fluid which enters the medullary collecting duct achieves osmotic equilibration. The loop of henle encompasses the thin descending limb, the thin ascending limb, and the tal. The loop of henle is a section of the nephron that leads from the proximal convoluted tubule to the distal convoluted tubule in the kidney. By means of a countercurrent multiplier system, which utilizes electrolyte pumps, the loop of henle creates an area of high urea concentration deep in the medulla, near the papillary duct in the collecting duct system. Physiological principles edit the term derives from the form and function of the loop of henle, which consists of two parallel limbs of renal tubules running in opposite. The loop of henle is a part of a nephron, a tiny tube inside the kidneys that filters solutes.
The first takes place in the region of the nephron called henles loop. Chlorothiazide is a sulfonamide loop diuretic that acts on the distal tubule and thick ascending limb of the loop of henle. The aims of the loop of henle is to reduce the volume of water and solutes within the urine but without changing the concentration. Summary of the countercurrent mechanism the primary engineis active salt reabsorption without water by the thick ascending limb of henles loop. What is flowing in the opposite direction to the glomerular filtrate for it to be called countercurrent can you please explain the countercurrent multiplier mechanism in the loop of henle in the nephron, including details about the ascending limb, descending limb and the collecting duct. Learn about how the loop of henle develops a concentration of 1200 mosml in the medulla of the kidney via a mechanism called.
There are actually two types of nephron in the kidney cortical and juxtamedullary. Loop of henle definition of loop of henle by medical. The main function of this structure is to reabsorb water and ions from the urine. An animation to explain the kidneys role in balancing h2o and electrolytes by creating a concentration gradient in the nephrons. He explains that the mechanism by which mammalian kidneys produce a. The countercurrent multiplier of the loop of henle is a challenging process to teach. Countercurrent multiplication is frequently mistaken for countercurrent exchange, a similar but different mechanism where gradients are maintained, but not established.
Transport of nacl without water in the thin and thick ascending limb of the loop of henle results in an interstitial osmolal gradient from 285 mosmolkg in the cortex, similar to plasma to 1200 mosmolkg in the medulla at the tip of the renal. The extrusion of sodium chloride from the ascending limb makes the surrounding interstitial fluid more. The loop of henle, however, is incompletely developed or absent in many nephrons of the bird kidney sperber, i960, and although many species appear able to produce a hypertonic urine the concentrating capacity of the kidney is considerably less than that of the mammal. Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some chemical, between two flowing bodies flowing in opposite directions to each other. Physiological role of the loop of henle in urinary. Within the nephron of the kidney, the ascending limb of the loop of henle is a segment of the heterogenous loop of henle downstream of the descending limb, after the sharp bend of the loop. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The first takes place in the region of the nephron called henle s loop. If youre seeing this message, it means were having trouble loading external resources on our website. Each kidney contains hundreds of thousands of individual nephrons, which pass between the cortex of the kidneys and the medulla, connecting to collecting ducts which route urine to the ureter so that it can be expressed. The ascending limb of the loop of henle is a direct continuation from the descending limb of loop of henle, and one of the structures in the nephron of the kidney. Loop of henle, long, ushaped portion of the tubule that conducts urine within each nephron q. Filtrate passing down the descending limb of the loop of henle is flowing in the opposite direction to fluid in the ascending limb. Countercurrent multiplier system and loop of henle.
The loop of henle is a specific portion of the nephron that is partially located in the renal cortex, and partly located in the renal medulla. Fluid entering the loop of henle is isotonic osmolarity 300 mosml but the volume is only a third of the volume originally filtered into bowmans capsule. The counter current multiplier in the loop of henle the kidney regulates the internal environment by judicious excretion of watersoluble plasma constituents and water. The presence of loop of henle enables birds and mammals including man to produce urine which is hypertonic to the blood.
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