waste), is an ultrafiltrate of the blood. The process in which fuid and smallprs
ID: 215142 • Letter: W
Question
waste), is an ultrafiltrate of the blood. The process in which fuid and smallprs ntahoile pass into the Bowman's capsule is known as titration (Figure 9 process in whch bloedn t 1400 L of blood pass through the kidneys every day, and the Bowmanis n cgublood plasma. This means that the kidneys filter the entire contents of the prosiconvlund sloodh consists primarily of water and is reabsorbed Iinto the nephrons t 180 L of fluid from this blood. The human body contains roughly 65 times every day Only about 1.S L of the daily Klerate is excreted as conveluted tubule bsorp Reabsta is filtered into the Bowman's capsule contains urea, water, ions, and other The Buni that are in the same concentrations as they are in the blood plasma. The Bowmants olehe proximal convoluted tubule, where reabsorption occurs (Figure 10). faid ad nutrients are transferred back into the interstitial fuaid vis both pas water, loadtivce methods. Specialized ion pumps transport potassium, K': sodium, corten sive and lorine, CI, from the filtrate into the fluid surrounding the tubule. Active ns, embedded in the walls of the tubale, reabsorb the amino acids her nutrients out of the filtrate. Urea and other unwanted compounds gluco bsorbed. The inner walls of the tubule are covered with microscopic exten- e not rred microvilli. These extensions greatly increase the total surface area that is ios cano threabsorption of solutes. All of the reabsorption processes make the botic to the interstitial fluid, and this causes water to flow out of the The movement of water is further elitated by membrane proteins called quaporins, or water channels, which form molecules to flow out of the tubule. The aquaporins abule and into the interstitial Buid by osmosis. oop of Henle passages for additional water 9 Filtration occurs in the that the maximum amount of water is removed from the tubule during the Figue Bowman's capsule. on process. The proximal convoluted tubule reabsorbs 67 % of theNa r. and a-; 65 % ofthe water; 50 % Of the urea; and nearly all of the arnino acids. clacose, and other nutrients. This highly efficlent process saves energy and alliows the minton tetrde deter, body to maximize the use of these nutrients. enter the peritubular capillaries. The remaining fluid, which has a high concentraseatinat and utnts back to the ineri i pessve and actve ranprt The nutrients and water that are reabsorbed in the proximal convoluted tubulke tion of urea and other wastes that are not reabsorbed, moves through the proximal coavoluted tubule into the descending portion of the loop of Henle. There, additional ubule water is reabsorbed by osmosis and the aquaporins. The outward movement of water concentrates the molecules and ions inside the tubule. As the fluid moves into the ascending portion of the loop of Henle, Na" and Cl are reabsorbed into the inter- stitial Buld. In the first part of the ascending segment, the concentrations are h enough to move Na" and Cl out of the tubule by passive diffusion. Toward the top of the ascending segment, these ions are moved out by active transport. Thus, as the uid Bows through the entire loop of Henle, water, nutrients, and ions have been com served and returned to the body fluids, and urea and other nitrogenous wastes have become concentrated in the filtrate so the total volume of the filtrate in the nephron has been greatly reduced corten medulla As the fluid continues along its path, it enters the distal convoluted tubule, where additional water and salts are removed. More ions and solutes move out of the fuid than nto ie this causes the further transport of water out of the tubule by osmosis through duct the The concentrated urea and other wastes flow into the collecting ducts, which further concentrate the urine. The collecting ducts descend from the cortex of the gh the medulla. They are permeable to water, but not to salt ions qaporins. The amounts of urea and other nitrogenous wastes remain the same loop of Henle Figure 10 Reabsorption occurs in the The concentration of solutes increases with depth as the fluid descends into the concentration of the urine. Near the bottom of the medulla, the walls of the col- Henle, and the distal convoluted tubule. o pas from the duct into the interstitial fluid. This urea adds significantdly to squpore a memtbrane prolein hat contain passive urea transporters, which allow some of the nitrogenous passively transports water molecules the concentration gradient of solutes in the medulla. 9.5 The Excretory System 45Explanation / Answer
The reabsorption is a process where the fluid that contain water, urea, ions etc. enter back into proximal convoluted tubule. Reabsorption is a process where the important nutrients, ions and minerals are sent to interstitial fluid with help of passive and active transport. The amino acid, glucose and nutrients is reabsorbed by active transport protein in the tubule walls and unwanted components like urea is not reabsorbed. The microvilli are present on the surface which increases the surface area that helps with reabsorption. There are special pores present known as aquaporins which helps in passage of water from tubule during the process of reabsorption.
The proximal tubule is responsible for reabsorbing 67% of Na+, K+ and Cl- along with 65% of water and 50% of urea. The waste and fluid which is not reabsorbed move through proximal convoluted tubule into loop of Henle where more water is again reabsorbed along with Na+ and Cl-. The ions move out by active transport in the ascending loop.
The fluid then enters the distal convoluted tubule which again reabsorbs additional water and salt along with more ions, water through osmosis and aquaporins. The concentrated urea and waste enters the collecting duct and descend from cortex of kidney through the medulla. The solute concentration increases as fluid descend into medulla and leads to removal of water through the ducts, increasing urine concentration. There are passive urea transporters in walls of collecting ducts allowing nitrogenous waste to pass.
Secretion
It is the process by which the waste is removed from blood and interstitial fluid and released in the urine. Some wastes are secreted in proximal convoluted tubule along with H+ and other components. The filtrate has many elements, ions and compounds that is secreted and once the urine reaches the collecting duct ready for excretion, all the important ions, nutrients and some water is reabsorbed.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.