Question

If Henle's loop were absent from mammalian nephron, which of the following is to be expected? (a) The urine will be more dilute. (b) There will be no urine formation. (c) The urine will have more concentration. (d) There will be hardly any change in the quality and quantity of urine formed.

Short answer

The correct answer is (a) The urine will be more dilute.

Step-by-step solution

Understanding the role of Henle's loop

Henle's loop is part of the nephron in the kidney which plays a key role in urine formation. It creates a concentration gradient in the interstitial fluid that surrounds the renal tubules. This concentration gradient allows for the reabsorption of water from the collecting ducts, making the urine more concentrated.

Predict the effect of absence of Henle's loop

If Henle's loop was absent from the nephron, there will not be any concentration gradient created in the interstitial fluid. This means that water reabsorption from the collecting ducts will be impaired. As a result, the final urine formed will be more diluted as less water will be reabsorbed.

Choose the correct option

Therefore, in absence of Henle's loop, the urine formed will be more diluted. So, the correct option is (a) The urine will be more dilute.

Key concepts

Nephron Structure

The nephron represents the fundamental structural and functional unit of the kidney, entrusted with the critical task of eradicating waste from the bloodstream and managing body fluids. Comprised of several intrinsic parts, each section plays a pivotal role in urine production.

Segments of the Nephron

An initial filtration takes place in the glomerulus, where blood plasma is sieved, allowing smaller molecules to pass into the proximal convoluted tubule. This area actively reabsorbs nutrients, ions, and water back into the bloodstream while directing waste and excess substances into the loop of Henle.The loop of Henle plunges into the kidney's medulla, forging a pivotal concentration gradient through its unique anatomy; a descending limb permeable to water but not to salts, contrary to an ascending limb, which permits salt to pass but is impervious to water. Culminating the process, the distal convoluted tubule and collecting duct regulate additional ion balance and water retention before channeling urine into the renal pelvis.

Importance of Nephron Configuration

An intricate network of blood vessels enwraps each nephron segment, facilitating the exchange of substances. The precise layout and connectivity of the nephron's parts are paramount for efficient filtration, reabsorption, and secretion, leading to the production of concentrated urine, a testament to the nephron's impeccable structural design.

Urine Concentration

Understanding urine concentration is vital as it mirrors the body's homeostasis and kidney function adeptness. The kidneys adjust urine concentration to preserve water when dehydrated and to eliminate excess water during hydration.

Mechanism of Urine Concentration

The kidneys meticulously curate urine concentration through a high saline region in the renal medulla, crafted by the loop of Henle. The descending limb of the loop allows for water efflux, raising the fluid's osmolarity as it descends. Contrarily, the ascending limb actively expels salts while restricting water permeability, thereby diminishing the osmolarity as the fluid ascends.Coupling with the gradient, the distal tubule and collecting duct, adjusted by the hormone antidiuretic hormone (ADH), further concentrates or dilutes the urine. ADH makes the collecting duct more permeable to water, so the descending fluid allies with the surrounding gradient, thereby heightening water reabsorption and yielding highly concentrated urine.

Consequences of Loop Disruption

Without the loop of Henle, the counter-current multiplier system would falter, disrupting the balance of water and salts and leading to more dilute urine as less water would be reabsorbed. A testament to this intricate system's efficiency is seen as individuals can survive on minimal water intake; their kidneys can intensify urine's concentration to conserve water.

Renal Physiology

Renal physiology encompasses the wide array of mechanisms in play within the kidneys that assure the constancy of internal conditions, often termed homeostasis. The kidneys' tasks are multifaceted and diverse, extending from waste excretion to meticulous fluid balance, and regulation of electrolytes.

Homeostatic Functions

The kidneys wield immense influence over the body's fluid volumes, electrolyte balance, and acid-base equilibrium. Through the production of urine, kidneys expel substances like urea, toxins, and excess ions. They also secrete hormones that regulate blood pressure, stimulate red blood cell production, and ensure the assimilation of calcium.

Embedded in these liabilities is the regulation of blood pressure, adeptly navigated through the alteration of fluid volume within the blood vessels—an undertaking steered by sodium and water reabsorption. Additionally, the kidneys contribute to blood pH stability by reabsorbing bicarbonate from urine and releasing hydrogen ions when necessary.

Integration with Cardiovascular System

Kidney function must be intricately synced with the cardiovascular system to manage blood filtration. Blood delivered to the kidneys is sifted through the glomeruli—capillary nests with a semi-permeable membrane that allows for the selective filtration that embarks on the path of urine formation.