Choose from the following a. glomerular capillaries b. bronchioles c. efferent a
ID: 3518163 • Letter: C
Question
Choose from the following
a. glomerular capillaries b. bronchioles c. efferent arterioles d. afferent arterioles e. descending limb of the loop of henel f. ascending limb of the loop of henle
g. bowmans capsule h. collecting duct i. proximal convoluted tubule
1. Reabsorption in this part of the nephron always results in an increase in filtrate osmolarity
2. After filtrate passes through this part of the nephron, it is called urine
3. The NKCC symporters help to maintain the countercurrent multiplier system in this part of the nephron.
Explanation / Answer
1. The descending limb of the loop of Henle is responsible for the increase of osmolarityof the filtrate. If we see the structure of Loop of Henle then we will see that this structure is originating from the functional unit of the kidney known as the nephrone. The nephrone is composed of the Bowman's capsule which is a cup like structure annd covers the blood capillaries. The toxic metabolites are filtered in this unit with the hepl of the concentration gradient of the components and then they are separated from the blood. The tubular structure which is originating from the capsule is called the peoximal convolutedtubule and from it the decending loop of henle starts and froms a hairpin like structure and passes through some distance in the renal medulla, from it then the ascending loop of henle arises and then it iscontinued with the distal convoluted tubule and the collecting ducts are continuous with the duct of Bellini. The glomerlar filtrate and the blood plasma is isotonic. They have the samme osmolarity. As this filtrate passes through the proximal convoluted tubule sodium, potassium, glucose, amino acids are reabsorbed from it along with proportionate water making it isotonic. So, this part leaves an isotonisc filtrate to pass through the descending loop of henle. The counter current exchange in the henle's loop retains and concentrates in the inner medulla the solutes like sodium, chloride, urea are reabsorbed from the ascending limb of loop of henle, the distal tubule and the collecting ducts and this makes the filtrate hypertonic or osmolarity of the filtrate increases. The fliud when it passes through the tip of the loop of henle then some amount of sodium and chloride ion diffuse back in to the filtrate.
2. After passing through the collecting ducts the filtrate is called urine. Because when the blood passes through the nephrone then only the filtration of some components take place and the final product urine is formed after filtration, reabsorption and secretion as the glomerular filtrate passes through the succssive structures of the kidney. In the proximal convoluted tubule sodium, chloride, glucose and amino acids are reabsorbed and along with this proportionate watter is also teabsorbed and isotonic urine passes through the descending limb of loop of henle. In this section water moves away from ithe filtrate and leads to reduced urine volume. The vasa recta and both limbs of loop of henle are responsible for the reabsorption of sodium, chloride and urea leaving a hypertonic filtrate. In the ascendind loop there is no movement of water and some amount of sodium and chloride ions are reabsorbed. This makes the filtrate diluted. In the distal convoluted tubules and the collecting ducts the sodium ion and chloride ionn are reabsorbed and there is no net movement of water. Vasopressin also stimulates the flow of water and reabsorption producing hypertonic filtrate. Urea, creatinine and uric acids are the substances which are secreted in to the fil trate in this course and magnesium, uric acid, phosphate ,calcium are reabsorbed from the filtrate. At the end of the tubule and in the collecting ducts the filtrate will now be called urine.
3. The NKCC symportes are found in the thick ascending limb of the loop of Henle. NKCC are the sodium-potassium-chloride cotransporters. This is a protein that actively transports these ions into the cells. NKCC has two subtypes and the NKCC2 is found in the kidney. They are also located in the macula densa of the kidney. They are located in the apex of the renal epithelial cells and they face the luminal side of the tube from which the urine flows. So these transporters can actively act on the passing fluid and they are responsible for the active reabsorption of sodium from the filtrate. This portion is also inpermiable to water. As in the other sections of the kidney soum reabsorption is coupled with water reabsorption where the structure is permiable to water. But in this section there isno movementof water and so the action of these symporters reduces urine osmolarity.