Human Kidney Function and Urine Regulation M 3.4

Filtrate that has the same osmotic pressure as its surrounding environment.

Part of the nephron where water is reabsorbed by osmosis.

Region of the kidney with higher osmolarity than the filtrate.

Section of nephron that reabsorbs sodium, potassium, and chloride, but is impermeable to water.

Process where reduced water reabsorption leads to urine with lower concentration of solutes.

Part of nephron where additional sodium chloride is reabsorbed and water impermeability occurs.

Antidiuretic hormone that regulates water reabsorption, concentrating urine.

The ability of kidneys to produce highly concentrated urine, 1200-1400 mOsm/L.

Urea cannot pass through certain kidney tubules, leading to increased concentration.

Antidiuretic hormone (ADH) increases water reabsorption in kidneys.

A process in the kidneys establishing osmolarity in the medullary interstitium.

These ducts have urea transporters that allow urea to diffuse out, raising interstitial osmolarity.

The kidneys can excrete highly concentrated or dilute urine based on solute needs.

The minimum urine volume required for excreting daily solutes, e.g., 2.5L for 600 million osmotic solutes.

Osmolarity affects the distribution of fluids; typically stable within 2-3%.

Sodium concentration in extracellular fluid is tightly controlled, ranging 104-145 MQ/L.

The segment of the nephron where tubular fluid is further diluted and sodium is actively transported out.

Antidiuretic hormone that regulates water reabsorption in the kidneys.

Tubular segment with variable water reabsorption depending on ADH presence.

Inner part of the kidney where osmolarity is maintained for urine concentration.

Concentration of solutes in a solution, important in urine formation.

The process where urea is passively reabsorbed from the tubular fluid into interstitial fluid.

Proteins that facilitate the diffusion of urea from the tubular fluid into renal interstitium.

Urine with high concentration due to significant water reabsorption and urea levels.

ADH (antidiuretic hormone) levels are highly sensitive to changes in plasma osmolarity.

The measure of solute concentration in blood plasma; affects ADH release significantly.

The body's system that regulates intake of fluids based on osmolarity and other factors.

Sensory cells that detect changes in plasma osmolarity and trigger ADH release.

Dehydration increases plasma osmolarity, stimulating ADH and thirst for fluid intake.

A hormone that stimulates thirst and increases blood pressure, acting outside the blood-brain barrier.

The osmotic receptor feedback system reduces fluid loss during dehydration.

The slight increase (2 mOsm/L) in osmolarity that activates the thirst response.

Regulates sodium concentration and osmolarity in extracellular fluid.

Hormone released to increase water reabsorption in kidneys.

Synthesizes ADH and regulates thirst and osmolarity.

Increases water permeability and reabsorbs water when ADH is present.

Water channels inserted in renal tubules to increase water reabsorption.

Process involves balancing water and solute concentrations in the body.

Stimuli that regulate ADH secretion in response to blood pressure changes.

Reabsorption of urea occurs in the thick limb, distal tubule, and cortical collecting duct with limited amounts due to low permeability.

UT A1 and UTA transporters facilitate urea diffusion into the medulla, increasing osmotic pressure to aid water reabsorption.

High urine flow decreases urine concentration and interstitial osmotic gradient, increasing urea excretion.

Healthy individuals excrete 20-60% of filtered urea, influenced by urine flow, hydration, and plasma urea concentration.

In renal disease, decreased GFR leads to higher plasma urea concentration and greater urea filtration and excretion.

In the proximal tubule, 40-50% of filtered urea is reabsorbed despite high concentration in the tubular fluid.

The thin loop of Henle secretes urea into tubular fluid, aided by the UT A2 transporter in combination with other transporters.

Renal medullary blood flow is low (less than 5% of total) and facilitated by the vasa recta as a counter current exchanger.