Nephron Segments and Reabsorption Mechanisms

<p>Excreted as urine (A)</p> Signup and view all the answers

<p>Thick Ascending Loop of Henle (B)</p> Signup and view all the answers

<p>Apical membrane (C)</p> Signup and view all the answers

<p>5% (D)</p> Signup and view all the answers

<p>It helps maintain fluid and electrolyte balance (B)</p> Signup and view all the answers

<p>Aldosterone (C)</p> Signup and view all the answers

<p>By inserting aquaporin channels in the apical membrane (C)</p> Signup and view all the answers

<p>Parathyroid hormone and vitamin D regulate calcium reabsorption. (B)</p> Signup and view all the answers

<p>It inhibits sodium reabsorption, opposing aldosterone. (D)</p> Signup and view all the answers

<p>Water channels are inserted only when AVP is present. (B)</p> Signup and view all the answers

<p>Secreting hydrogen and bicarbonate while reabsorbing potassium. (A)</p> Signup and view all the answers

<p>The macula densa detects sodium and chloride levels delivered to the DCT. (D)</p> Signup and view all the answers

<p>AVP increases water reabsorption to produce concentrated urine. (D)</p> Signup and view all the answers

<p>It pumps three sodium ions out of the cell for every two potassium ions it moves in. (B)</p> Signup and view all the answers

<p>Glucose (C)</p> Signup and view all the answers

<p>Thin descending loop (A)</p> Signup and view all the answers

<p>Controlling calcium excretion (B)</p> Signup and view all the answers

<p>Sodium-glucose co-transporter (C)</p> Signup and view all the answers

<p>A sodium-potassium-chloride co-transporter transports sodium and chloride into the cell. (B)</p> Signup and view all the answers

<p>It creates a concentration gradient of sodium. (A)</p> Signup and view all the answers

<p>They block chloride reabsorption in the thick ascending loop of Henle. (D)</p> Signup and view all the answers

<p>It produces prostaglandin and renin. (B)</p> Signup and view all the answers

<p>It follows sodium due to osmotic pressure. (C)</p> Signup and view all the answers

<p>5-8% of the filtered sodium. (A)</p> Signup and view all the answers

<p>It enhances sodium and water excretion. (B)</p> Signup and view all the answers

<p>It reabsorbs sodium while secreting hydrogen ions. (C)</p> Signup and view all the answers

The process by which substances from the blood are filtered into the nephron.

The movement of substances from the blood into the tubular lumen.

The movement of substances from the tubular lumen back into the blood.

The site where filtration occurs. It's the beginning of the nephron.

The point where the tubular system meets the capillary system for the second time. It regulates filtration rate.

The side of the cell layer facing the lumen in the tubular system.

The side of the cell layer facing away from the lumen in the tubular system.

An acronym used to remember the parts of the tubular system: Lumen, Apical membrane, Basolateral membrane.

The distal convoluted tubule (DCT) plays a significant role in regulating fluid balance and electrolyte levels in the kidneys. It's responsible for fine-tuning the composition of urine before it's excreted.

In the DCT, sodium and chloride co-transporters actively reabsorb these ions, contributing to electrolyte balance and blood volume regulation. This process can be inhibited by thiazide diuretics.

Calcium reabsorption in the DCT is regulated by hormonal signals, primarily parathyroid hormone (PTH) and vitamin D. These hormones play a crucial role in maintaining blood calcium levels.

The collecting tubule is the final segment of the nephron where filtered fluid is collected and further modified before being drained into the renal pelvis. It plays a crucial role in water and electrolyte balance.

In the collecting tubule, intercalated cells actively regulate acid-base balance. They secrete hydrogen ions (H+) and bicarbonate (HCO3-) and reabsorb potassium (K+) to maintain pH within the body.

The collecting duct's permeability to water is tightly controlled by the hormone arginine vasopressin (AVP). AVP increases water reabsorption by inserting aquaporin channels into the collecting duct cells, allowing water to move out of the filtrate and back into the bloodstream.

Aldosterone, a hormone released by the adrenal glands, promotes sodium reabsorption in the collecting tubule. It increases sodium reabsorption by inserting sodium channels into the apical membrane of collecting tubule cells.

The countercurrent multiplier system creates a high sodium concentration gradient in the medulla, which drives water reabsorption from the collecting tubule. When AVP is present, water channels are inserted into the collecting tubule, allowing water to move out of the filtrate and into the hypertonic interstitium, resulting in concentrated urine.

Sodium moves from the tubular lumen into the tubular cell across the apical membrane, then into the blood vessels through the basolateral membrane thanks to the sodium-potassium pump.

This pump is located on the basolateral membrane and actively moves three sodium ions out of the cell for every two potassium ions moved into the cell, consuming energy (ATP).

The PCT is the first part of the renal tubule after the Bowman's capsule, where most reabsorption of fluid and solutes (67% of the filtered load) occurs.

The PCT reabsorbs important substances like glucose, sodium, chloride, water, and bicarbonate, while secreting hydrogen ions and other waste products.

Sodium-glucose co-transporter (SGLT) on the apical membrane brings glucose and sodium into the cell, while the sodium-hydrogen exchanger reabsorbs sodium and secretes hydrogen.

The loop of Henle is a U-shaped segment following the PCT, with a descending limb permeable to water but not ions, and an ascending limb permeable to ions but not water.

The loop of Henle's main function is to create a hyperosmotic interstitium in the medulla, which is the tissue surrounding the tubules and blood vessels.

The thin descending limb is only permeable to water due to aquaporin channels, while the thick ascending limb actively transports sodium out, making the interstitium fluid more concentrated.

The countercurrent system describes the opposing flow of blood and filtrate in the loop of Henle, creating a sodium concentration gradient which is important for concentrating urine in the collecting tubule.

The DCT is the next segment after the loop of Henle, responsible for fine-tuning salt and water excretion, and playing a crucial role in calcium regulation.

The DCT reabsorbs a smaller amount of filtered sodium and chloride than the PCT, using sodium-chloride co-transporter, which can be inhibited by thiazide diuretics.

Tubuloglomerular feedback occurs at the macula densa, where decreased GFR leads to decreased sodium and chloride delivery, triggering the release of prostaglandin and renin.

Renin leads to the production of angiotensin II, which constricts the efferent arteriole, increasing pressure in the glomerulus and raising GFR.

Loop diuretics block the chloride reabsorption in the thick ascending loop of Henle, preventing sodium and water reabsorption and lowering blood pressure.

Thiazide diuretics inhibit the sodium-chloride co-transporter in the DCT, leading to decreased sodium and water reabsorption, also lowering blood pressure.

Combining loop and thiazide diuretics can enhance sodium and water excretion, especially in conditions like heart failure, but requires careful monitoring of blood pressure and electrolytes.