Renal Physiology Overview

The process of the renal tubules reclaiming water, nutrients, and ions from the filtrate back into the bloodstream.

The active transport of sodium ions out of the tubule cells into the peritubular capillaries, driving the reabsorption of other substances.

The maximum rate at which a substance can be reabsorbed by the renal tubules, determined by the number of available transport proteins.

The constant reabsorption of water occurring in the proximal convoluted tubule due to osmosis, independent of antidiuretic hormone (ADH).

The variable reabsorption of water occurring in the collecting ducts under the influence of antidiuretic hormone (ADH).

Water reabsorption in the nephron loop is not tied to solute reabsorption. Descending limb lets water out but not solutes. Ascending limb lets solutes out, water stays in.

Antidiuretic hormone (ADH) increases water reabsorption by inserting aquaporins (water channels) into collecting duct cells.

Aldosterone promotes sodium reabsorption in the collecting ducts and distal convoluted tubule. Water follows sodium.

ANP reduces blood sodium, decreasing blood volume and pressure.

Reabsorption in the distal convoluted tubule and collecting duct is controlled by hormones like ADH, aldosterone, and ANP; Ca2+ by PTH.

increases calcium reabsorption in the distal convoluted tubule.

Sodium reabsorption, controlled by hormones (e.g., aldosterone), is vital to maintain blood volume and pressure. Loss of too much sodium is dangerous.

The fluid that fills the spaces between cells in the kidney.

The concentration of solutes in a solution, specifically in a fluid.

Concentration of solutes in the filtrate as it moves through the descending loop.

Concentration of solutes in the filtrate as it moves through the ascending loop.

A system in the kidney that prevents rapid salt removal and preserves the kidney's osmotic gradient.

Blood vessels that surround the nephron loop, maintaining the osmotic gradient.

The concentration difference between the kidney's outer and inner regions.

The portion of the nephron that creates the osmotic gradient in the kidney.

Having the same concentration of solutes as a solution.

Isosmotic to blood plasma and cortical interstitial fluid.

Hypo-osmotic to interstitial fluid at 100 mOsm.

Water moves out, concentrating filtrate.

Increased osmolality due to Na+ and Cl- pumping.

Movement of substances across a membrane without energy.

Movement of substances across a membrane with energy.

100 mOsm in the nephron loop.

Outer region of the kidney.

The volume of filtrate formed per minute by both kidneys. It reflects the efficiency of kidney function.

A specialized structure within the glomerulus composed of three layers: endothelium of glomerular capillaries, basement membrane, and podocyte foot processes. It allows water and small solutes to pass through while blocking larger molecules.

1. Filtration: Occurs in the glomerulus, where blood is filtered to form filtrate.
2. Reabsorption: Specific substances like water, glucose, and ions are reabsorbed from the filtrate back into the bloodstream along the nephron.
3. Secretion: Waste products and excess substances are actively transported from the blood into the filtrate.

Reabsorption moves substances from the filtrate back into the blood, while secretion moves substances from the blood into the filtrate.

The loop of Henle creates an osmotic gradient in the medulla. This gradient allows for the reabsorption of water from the collecting ducts, resulting in concentrated urine.

The descending limb is permeable to water but not solutes, allowing water to move out. The ascending limb is permeable to solutes (like Na+) but not water, allowing solutes to leave.

Antidiuretic hormone (ADH) causes the collecting ducts to insert aquaporins (water channels) into their membranes, increasing water reabsorption.

Aldosterone promotes sodium reabsorption in the collecting ducts and distal convoluted tubule. Water follows sodium.

Atrial natriuretic peptide (ANP) reduces blood sodium, decreasing blood volume and pressure.

Parathyroid hormone (PTH) increases calcium reabsorption in the distal convoluted tubule.

The nephron loop creates an osmotic gradient where the filtrate becomes more concentrated as it descends and less concentrated as it ascends.

The descending limb of the nephron loop is permeable to water but not to solutes. Water moves out of the tubule, making the filtrate more concentrated.

The ascending limb of the nephron loop is permeable to solutes but not to water. Sodium and chloride ions are actively transported out of the tubule, making the interstitial fluid more concentrated.

Sodium and chloride ions are actively transported out of the ascending limb of the nephron loop, requiring energy.

The countercurrent mechanism in the nephron loop helps maintain the osmotic gradient by preventing the rapid removal of salt from the medulla.

The filtrate leaving the nephron loop is hypo-osmotic to the interstitial fluid. It's more dilute than the surrounding fluid.

The process in the nephron loop that creates a high osmotic concentration in the medulla of the kidney, allowing for concentrated urine production. It involves actively transporting salt out of the ascending limb, making the interstitial fluid hyperosmotic and causing water to move out of the descending limb, leading to a concentration gradient.

The descending limb of the nephron loop is permeable to water but not to NaCl. It allows water to move out of the filtrate, becoming more concentrated, as it descends into the increasingly hyperosmotic medullary interstitial fluid.

The ascending limb of the nephron loop is impermeable to water but actively pumps out NaCl. This creates a hyperosmotic interstitial fluid in the medulla, contributing to the osmotic gradient.

The osmotic gradient, created by the countercurrent multiplier, allows the kidney to produce concentrated urine. Water is reabsorbed from the filtrate, driven by the high osmolality of the medullary interstitial fluid, leading to urine that can be more concentrated than blood plasma.

The vasa recta acts as a countercurrent exchanger, minimizing the washout of the osmotic gradient established by the countercurrent multiplier. They allow for the exchange of water and solutes between the blood and the interstitial fluid, but maintain the overall concentration gradient.

The filtrate becomes more concentrated as it descends through the loop because it loses water to the hyperosmotic medullary interstitial fluid. The descending limb is permeable to water but not to NaCl, causing water to move out, increasing the concentration of solutes in the filtrate.

The nephron loop plays a crucial role in regulating urine concentration by establishing a high osmotic gradient in the medulla. This gradient allows for the reabsorption of water from the filtrate, creating concentrated urine when necessary. The countercurrent multiplier system utilizes the opposing flow in the loop and the active transport of salt to achieve this.

The ascending limb of the nephron loop is impermeable to water but actively pumps out NaCl. This contributes to the hyperosmotic interstitial fluid in the medulla, which is crucial for the countercurrent multiplier system and the concentration of urine.

Blood plasma is the liquid portion of blood, containing various solutes and proteins. Glomerular filtrate is the fluid that is filtered from blood in the glomerulus, lacking cells and most proteins. Urine is the final product of the kidney, after further modifications to the filtrate, containing waste products and excess solutes.

The three processes are glomerular filtration, tubular reabsorption, and tubular secretion. Filtration occurs in the glomerulus, reabsorption in the tubules, and secretion in the collecting ducts.

The juxtaglomerular apparatus (JGA) is located in the nephron where the distal convoluted tubule contacts the afferent arteriole. It regulates blood pressure and GFR by releasing renin.

Diuretics increase urine production by interfering with the reabsorption of water and solutes in the nephron, resulting in a larger volume of dilute urine.

Aldosterone targets the collecting ducts and distal convoluted tubule, promoting sodium reabsorption. Water follows sodium, leading to increased blood volume and pressure.

Released by the posterior pituitary, ADH causes the collecting ducts to insert aquaporins into their membranes, facilitating water reabsorption. This results in more concentrated urine.

Atrial natriuretic peptide (ANP) is released by heart cells when blood volume or pressure is high. It works to decrease sodium in the blood, reducing blood volume and pressure.

Parathyroid hormone (PTH) acts on the distal convoluted tubule to increase calcium reabsorption, regulating blood calcium levels.

The inner region of the kidney, with a concentration gradient important for water reabsorption.

This hormone increases water reabsorption by inserting aquaporins (water channels) into the collecting duct cells.

Permeable to water but not solutes, meaning water leaves the filtrate and it becomes concentrated as it goes down.

Permeable to solutes but not water, meaning solutes leave the filtrate and the surrounding interstitial fluid becomes salty.

These blood vessels surround the nephron loop, maintaining the osmotic gradient by exchanging water and solutes.

The descending limb of the nephron loop is permeable to water but not solutes. This allows water to move out of the filtrate, making it more concentrated as it descends into the increasingly hyperosmotic medullary interstitial fluid.

The ascending limb of the nephron loop is impermeable to water but actively pumps out NaCl. This creates a hyperosmotic interstitial fluid in the medulla, contributing to the osmotic gradient.

A concentration difference between the inner (medulla) and outer (cortex) regions of the kidney, created by the countercurrent multiplier. This gradient allows for the reabsorption of water from the filtrate, leading to concentrated urine.

Blood vessels surrounding the nephron loop that act as countercurrent exchangers. They prevent rapid salt removal from the medulla, preserving the osmotic gradient and ensuring efficient water reabsorption.

A type of nephron with long nephron loops that extend deep into the medulla, contributing significantly to the osmotic gradient and allowing for the production of concentrated urine.

The countercurrent multiplier system involves the active transport of salt out of the ascending limb of the nephron loop, creating a hyperosmotic interstitial fluid in the medulla. This draws water out of the descending limb, making the filtrate more concentrated as it descends. The loop's countercurrent flow (opposite directions) amplifies this effect, leading to a high osmotic concentration in the medulla.

The vasa recta, blood vessels surrounding the nephron loop, act as countercurrent exchangers. They prevent the rapid washout of the medullary osmotic gradient established by the countercurrent multiplier, allowing for efficient water reabsorption and concentrated urine production.

The first step in urine formation where blood is filtered in the glomerulus, creating a cell- and protein-free filtrate called glomerular filtrate.

The active transport of waste products and excess substances from the blood into the filtrate in the tubules, ensuring their removal in urine.

The juxtaglomerular apparatus (JGA) is a specialized structure that helps regulate blood pressure and glomerular filtration rate (GFR) by releasing renin.

The active transport of sodium (Na+) ions out of the tubule cell into the peritubular capillaries.

The movement of a substance across a membrane using the energy stored in the concentration gradient of another substance.

Protein channels in the cell membrane that allow water to pass through by osmosis.