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Related Concept Videos

Physiology of the Genitourinary System III: Urine Concentration and Dilution01:20

Physiology of the Genitourinary System III: Urine Concentration and Dilution

The kidneys concentrate or dilute urine to maintain water and electrolyte balance. Nephrons, particularly the loop of Henle, play a crucial role in this process through the countercurrent multiplication system. This system establishes a high osmolarity in the renal medulla, which is essential for water reabsorption. In the loop of Henle’s descending limb, water is reabsorbed into the surrounding medulla due to its permeability to water. In contrast, the ascending limb actively transports...
Formation of Dilute Urine01:20

Formation of Dilute Urine

The formation of dilute urine is a critical renal adaptation that maintains fluid balance, particularly during periods of high fluid intake. This process primarily involves the juxtamedullary nephrons. By adjusting the permeability of water and ions in response to physiological conditions, the kidneys can either conserve or excrete water, resulting in concentrated or dilute urine.
Filtrate Osmolarity in the PCT
Initially, as the filtrate passes through the proximal convoluted tubule (PCT), its...
Formation of Concentrated Urine01:23

Formation of Concentrated Urine

There is a gradient of solutes in the interstitial fluid from the renal cortex through the medulla, known as the medullary osmotic gradient. The juxtamedullary nephrons establish and maintain this gradient using countercurrent mechanisms with loops extending deep into the medulla. These nephrons also use countercurrent mechanisms to regulate urine volume and concentration. The interaction between the descending and ascending limbs of the nephron loop creates an osmotic gradient through...
Physiology of the Genitourinary System II: Tubular Reabsorption and Secretion01:22

Physiology of the Genitourinary System II: Tubular Reabsorption and Secretion

The kidneys maintain homeostasis through filtration, reabsorption, and secretion. Tubular reabsorption and secretion are crucial in forming urine and regulating electrolytes, water balance, and waste elimination.Tubular Reabsorption and Secretion ProcessesTubular reabsorption is the process that reclaims essential substances such as electrolytes, glucose, amino acids, and water from the glomerular filtrate back into the bloodstream. This is achieved through passive and active transport...
Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Excretion01:18

Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Excretion

In geriatric patients, renal physiology undergoes significant changes, including diminished renal blood flow and a lower glomerular filtration rate (GFR), leading to alterations in medication clearance. Drugs such as aminoglycoside antibiotics, lithium, and digoxin, which rely on glomerular filtration for removal from the body, particularly impact pharmacokinetics. These drugs tend to have slower clearance rates in older adults, necessitating careful dosage considerations.Evaluation of renal...
Physiology of Urine Formation01:24

Physiology of Urine Formation

Urine formation is an essential function of the human body. It plays a critical role in maintaining homeostasis by regulating the volume and composition of body fluids. The kidneys, the primary organs involved in this process, filter blood to remove waste products and excess substances, ultimately producing urine.
Glomerular Filtration
The first stage in urine formation is glomerular filtration. Each kidney contains approximately 1 million nephrons, the functional units of filtration, with a...

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Related Experiment Video

Updated: May 22, 2026

Using 2-Photon Microscopy to Quantify the Effects of Chronic Unilateral Ureteral Obstruction on Glomerular Processes
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Urine concentrating and diluting ability during aging.

Jeff M Sands1

  • 1Renal Division, Department of Medicine, Emory University School of Medicine, WMRB Room 338, NE, 1639 Pierce Drive, Atlanta, GA 30322, USA. jeff.sands@emory.edu

The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
|May 17, 2012
PubMed
Summary
This summary is machine-generated.

Aging reduces the kidney

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Last Updated: May 22, 2026

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Quantitative Real-Time Polymerase Chain Reaction Evaluation of MicroRNA Expression in Kidney and Serum of Mice with Age-Dependent Renal Impairment
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Quantitative Real-Time Polymerase Chain Reaction Evaluation of MicroRNA Expression in Kidney and Serum of Mice with Age-Dependent Renal Impairment

Published on: April 29, 2022

Area of Science:

  • Gerontology and Nephrology

Background:

  • Normal aging is associated with a decline in urine concentrating ability in both humans and rats.
  • Reduced kidney function in aging can impact water balance and electrolyte regulation.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying age-related decline in urine concentrating ability.
  • To examine the abundance and response of key renal transport proteins in aged rats.

Main Methods:

  • Comparative analysis of kidney medulla protein abundance in young and aged rats.
  • Assessment of protein responses to water restriction in different age groups.

Main Results:

  • Aged rats exhibited reduced abundance of key water, sodium, and urea transport proteins in the kidney medulla.
  • These proteins showed diminished responsiveness to water restriction in aged rats compared to younger ones.
  • Reduced protein levels and function correlate with impaired urine concentrating and water conservation abilities.

Conclusions:

  • Age-related decreases in renal transport proteins contribute to reduced urine concentrating capacity.
  • These findings in rats may offer molecular insights into similar age-related changes in human kidneys.
  • Potential for therapeutic strategies targeting these proteins to improve kidney function in aging and nocturnal polyuria.