Which nephron segments reabsorb water

Solutes from the blood are filtered in the glomerulus and enter the nephron, specifically, Bowman's capsule. Both blood pressure and oncotic force pressure in the glomerulus due to proteins affect filtration rate. Together, the glomerulus and Bowman's capsule are known as the renal corpuscle. The glomerular basement membrane—which sits between capillary endothelial cells and the selectively permeable podocytes that line Bowman's capsule—is comprised of negatively charged proteins that repel other negatively charged proteins.

This helps prevent these compounds from entering the nephron with the filtrate. Glucose does not get reabsorbed because the epithelia between the glomerulus and the Bowman's capsule prevent filtration of glucose.

Aquaporins facilitate the transport of glucose from the tubule lumen to the proximal tubule cells. Sodium is coupled with glucose via a cotransporter, allowing it to enter the proximal tubule cells from the tubule lumen. Once in the proximal tubule cells, glucose then passes through a Glut-2 transmembrane carrier protein, but only on the basolateral membrane of the proximal tubule cells from proximal tubule cells to the interstitual fluid. Kidneys contain small structures called nephrons that function to create urine.

Urine is created by filtering the incoming blood. The blood enters the nephron via the glomerulus. Each segment has varying permeabilities for ions and water. The nephron segment that is only permeable to water is the descending loop of Henle. As urine travels down this segment, water gets reabsorbed back into the blood whereas the solutes remain in the urine because the descending loop of Henle is impermeable to solutes.

This makes the urine very concentrated. The ascending loop of Henle has opposite permeabilities. Solutes, such as ions, are permeable and can cross the wall and be reabsorbed into the blood; however, water is impermeable. The proximal convoluted tubule is the site of most of the reabsorption and secretion of molecules; therefore, both water and solutes are permeable here.

The collecting duct is not part of the nephron. Multiple nephrons drain into a collecting duct. Collecting ducts are sites of further reabsorption and secretion; therefore, both water and ions are permeable. Note that reabsorption is the process of moving substances solutes or water from urine to the blood whereas secretion is the process of moving substances from the blood to urine.

The urine gets processed reabsorption or secretion in different nephron segments before being ultimately excreted. During this process, the urine also called tubular fluid is transported via tubes called renal tubules; therefore, this is the site of reabsorption and secretion.

A nephron begins at the renal corpuscle and ends at the distal convoluted tubule. The collecting duct, on the other hand, is not part of a nephron. Multiple nephrons drain their tubular fluid into a single collecting duct.

The tubular fluid is further filtered in the collecting duct and is ultimately excreted as urine. The distal convoluted tubule last part of a nephron is connected to the collecting duct. The latter third of a nephron also processes the fluid; however, it is negligible when compared to the proximal tubule. Most of the urine is created in the nephron. The tubular fluid traverses each nephron segment, where it is processed.

The final fluid that enters the collecting duct is processed further, but most of the urine that is excreted comes from the nephron. Kidneys can be divided into two parts: renal cortex and renal medulla. The medulla is the inner part; it contains the ascending and descending limbs of the loop of Henle, and the portion of renal tubule that descends into the medulla.

The proximal convoluted tubule and the distal convoluted tubule are not part of the loop of Henle and, therefore, are found in the renal cortex. Note that the nephron begins at the renal corpuscle in the cortex, becomes the proximal tubule in the cortex , descends into the medulla as loop of Henle, and rises back into the cortex as the distal tubules. The tubular fluid in distal tubules drains into the cortical collecting duct the region of the collecting duct found in the cortex , which eventually enters the medullary collecting duct and leaves the kidney as urine.

If you've found an issue with this question, please let us know. With the help of the community we can continue to improve our educational resources. Unless these substances are reabsorbed in later segments of the nephron, they will be excreted from the body.

The first part of the nephron that is responsible for water reabsorption is the proximal convoluted tubule. Filtered fluid enters the proximal tubule from Bowman's capsule. Many substances that the body needs, which may have been filtered out of the blood at the glomerulus, are reabsorbed into the body in this segment.

As these other substances are reabsorbed, water is also reabsorbed through osmosis. The next site of water reabsorption is in the loop of Henle. The loop of Henle is shaped like a "U", with a descending limb and an ascending limb. Filtered fluid first passes through the descending limb. Here, water flows out of the tubule into the surrounding tissue, as the walls of the nephron are permeable to water in this part of the structure. The surrounding tissue is now more dilute than the filtered fluid in the tubule.

As a result, the filtered fluid loses salt as it passes through the ascending limb. The initial segment of the distal convoluted tubule lies right next to the glomerulus and forms the juxtaglomerular apparatus. The juxtaglomerular apparatus is a specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole.

It is located near the vascular pole of the glomerulus. The main function of the apparatus is the secretion of renin, which regulates systemic blood pressure via the renin-angiotensin-alodosterone system.

The juxtaglomerular apparatus is composed of:. The terminal portion of the distal tubule empties through collecting tubules into a straight collecting duct in the medullary ray.

The collecting duct system is under the control of antidiuretic hormone ADH. When ADH is present, the collecting duct becomes permeable to water. Numerous collecting ducts merge into the renal pelvis, which then becomes the ureter. The ureter is a muscular tube, composed of an inner longitudinal layer and an outer circular layer. The lumen of the ureter is covered by transitional epithelium also called urothelium.

Recall from the Laboratory on Epithelia that the transitional epithelium is unique to the conducting passages of the urinary system. Its ability to stretch allows the dilation of the conducting passages when necessary. The ureter connects the kidney and the urinary bladder. The ureter empties the urine into the bladder. The transitional epithelium continues over the surface of this organ. The thickened muscular layers become interwoven and cannot be clearly identified at this point. The urethra carries the urine away from the bladder to the outside of the body.

In the male, it is joined by the genital system. The epithelium changes from transitional to stratified or pseudostratified columnar in the urethra, and to stratified squamous in the distal end of the urethra. Answer: Podocyte: Foot processes assist in filtration barrier function by repelling negatively-charged molecules.

Mesangial Cell: Provides structure support and regulate diameter of capillaries. Macula Densa: Senses blood pressure, regulates blood flow in afferent arteriole to maintain the glomerular filtration rate and stimulates release of renin.

Juxtaglomerular Complex: synthesize, store and release renin. Answer: The ureter and bladder have a transitional epithelium. The initial segment of the urethra has a stratified epithelium, and the final segment has a stratified squamous epithelium.

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