key term - Loop of Henle

Definition

The loop of Henle is a U-shaped section of the nephron located between the proximal tubule and the distal tubule in the kidney. It plays a critical role in concentrating urine and regulating water balance in the body, utilizing its unique structure to create a concentration gradient that aids in water reabsorption.

5 Must Know Facts For Your Next Test

1. The loop of Henle consists of a descending limb and an ascending limb, each with distinct permeabilities that facilitate water and ion transport.
2. In the descending limb, water is reabsorbed while the tubular fluid becomes more concentrated due to the higher osmolarity of the surrounding interstitial fluid.
3. The ascending limb is impermeable to water but allows for active transport of sodium and chloride ions out of the tubular fluid, which dilutes it.
4. The loop of Henle's structure contributes significantly to the kidney's ability to produce urine that is either concentrated or dilute, depending on hydration levels.
5. The efficiency of the loop of Henle in concentrating urine can be affected by various factors, including hydration status and hormonal influences like antidiuretic hormone (ADH).

Review Questions

• How does the structure of the loop of Henle contribute to its function in urine concentration?
  • The loop of Henle has a unique U-shaped structure with a descending limb that is permeable to water and an ascending limb that actively transports ions. This arrangement allows for countercurrent multiplication, where water moves out of the descending limb into the hyperosmotic medullary interstitium, concentrating the tubular fluid. Simultaneously, ions are transported from the ascending limb into the interstitium, further enhancing osmolarity and enabling efficient water reabsorption in the collecting ducts.
• Discuss how countercurrent multiplication within the loop of Henle affects overall kidney function and homeostasis.
  • Countercurrent multiplication in the loop of Henle creates a high osmolarity gradient in the renal medulla, which is crucial for the kidneys' ability to concentrate urine. This process allows for efficient reabsorption of water as it passes through the collecting ducts, which is essential for maintaining fluid balance and homeostasis in the body. If this mechanism is disrupted, it could lead to conditions such as dehydration or overhydration, affecting overall health.
• Evaluate how hormonal regulation influences the function of the loop of Henle in relation to water reabsorption and body fluid homeostasis.
  • Hormonal regulation significantly impacts how effectively the loop of Henle functions in maintaining body fluid homeostasis. Antidiuretic hormone (ADH), for instance, increases water permeability in the collecting ducts, allowing more water to be reabsorbed based on the osmotic gradient created by the loop. When ADH levels are high, more concentrated urine is produced, while low levels lead to dilute urine. This regulation is vital for adapting to varying hydration statuses and ensuring fluid balance within the body.

Related terms

Nephron: The basic structural and functional unit of the kidney, responsible for filtering blood and forming urine.

Countercurrent Multiplication: A mechanism in the kidneys that uses the flow of fluid in opposite directions through the loop of Henle to create a concentration gradient for water reabsorption.

Osmosis:

The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.