Physiology of Water Reabsorption in Collecting Duct

A type of kidney cell that responds to acidosis (higher than normal acidity) by releasing bicarbonate (HCO3-) and protons (H+), effectively reducing acidity in the blood.

The equation CO2 + H2O  H2CO3  H+ + HCO3– represents the formation of carbonic acid (H2CO3) from carbon dioxide (CO2) and water (H2O), which then dissociates into a proton (H+) and bicarbonate (HCO3-).

The process by which intercalated A-cells remove protons (H+) from the blood by pumping them into the urine using the H-K-ATPase pump, while simultaneously bringing potassium (K+) into the cell.

A type of kidney cell that responds to alkalosis (higher than normal alkalinity) by taking up protons (H+) and releasing bicarbonate (HCO3-), effectively increasing acidity in the blood.

The transporter in the cell membrane of both A and B Intercalated cells used to move bicarbonate (HCO3-) in or out of the cell, depending on the pH level.

The final segment of the nephron where fine-tuning of urine composition takes place, adjusting water, electrolytes, and acid-base balance.

The main cell type in the collecting duct responsible for regulating water reabsorption and sodium levels.

Specialized cells within the collecting duct that play a key role in maintaining acid-base balance in the body. They can secrete either acid (H+) or bicarbonate (HCO3-) based on the body's needs.

A special type of blood vessel that runs alongside the nephron, allowing for exchange of substances (like urea) between the blood and the collecting duct. Helps regulate water and solute balance.

The process by which urea, a waste product, is recycled back to the nephron from the vasa recta to help regulate urine concentration and fluid balance. Helps keep the body hydrated.

The movement of water and solutes from the collecting duct into the blood. This is a critical process for maintaining fluid volume and electrolyte balance.

Antidiuretic hormone (ADH) increases the expression of aquaporin-2 in the collecting duct. This aquaporin transports water from the filtrate back into the bloodstream, leading to concentrated urine.

Principal cells in the collecting duct are responsible for regulating sodium and potassium levels in the body. They achieve this by reabsorbing sodium and excreting potassium.

Intercalated A-cells play a crucial role in maintaining acid-base balance. They respond to acidosis (increased acidity) by secreting protons (H+) and reabsorbing bicarbonate (HCO3-).

Intercalated B-cells are essential in managing alkalinity. They respond to alkalosis (decreased acidity) by reabsorbing protons (H+) and secreting bicarbonate (HCO3-).

The collecting duct is the final segment of the nephron where fine-tuning of urine concentration and electrolyte balance occurs.

A hormone released by the posterior pituitary gland in response to high plasma osmolality. It increases water reabsorption by the kidneys, helping concentrate urine and raise blood volume, ultimately bringing plasma osmolality back to normal.

The measure of solute concentration in a solution, specifically the number of solute particles per unit volume of solvent.

A state where the solute concentration is higher than the solvent concentration, often leading to water moving out of cells.

A state where the solute concentration is lower than the solvent concentration, often leading to water moving into cells.

A state where the solute concentration is equal to the solvent concentration, maintaining a balanced equilibrium in cells and fluids.

A key factor that triggers the release of ADH; it occurs when the plasma osmolality is higher than normal, indicating a need for water retention to dilute the solutes.

A hormone that plays a role in increasing blood pressure. It can also stimulate ADH release, further contributing to water reabsorption and increased blood volume.

A protein that binds to ADH on the principal cells of the collecting duct, initiating a cascade of intracellular events that ultimately activate Aquaporin-II channels.

A type of channel protein inserted into the cell membrane of principal cells in response to ADH. They allow water to flow from the tubular fluid into the blood, increasing water reabsorption and urine concentration.

PTH (Parathyroid Hormone) is essential for the reabsorption of calcium from the kidneys. It helps regulate calcium levels in the blood.

The majority of water reabsorption occurs in the proximal convoluted tubule (PCT), followed by the descending limb of the loop of Henle, and then the distal convoluted tubule (DCT).

Aquaporin-II, a special protein channel, regulates water permeability in the collecting duct based on ADH (anti-diuretic hormone) levels. Higher ADH levels mean more water is reabsorbed.

The majority of sodium reabsorption occurs in the proximal convoluted tubule (PCT), followed by the ascending limb of the loop of Henle and the early DCT. The remaining sodium reabsorption is controlled by aldosterone.

The counter-current multiplier mechanism in the loop of Henle creates a concentration gradient in the medulla, causing water to flow out of the descending limb and solutes to be pumped into the ascending limb.

The process of obligatory water reabsorption refers to the passive movement of water from the descending limb of the loop of Henle into the surrounding interstitium. It is driven by the concentration gradient created by the counter-current mechanism.

Urea recycling primarily serves to contribute to the medullary concentration gradient, which is essential for the kidney to produce concentrated urine.

Facilitated diffusion is the process by which urea passively moves from the collecting duct into the medullary interstitium. It is driven by the existing concentration gradient between the two compartments.