- Concentration of urine in mammals depends on
(1) Glomerulus’s size
(2) Length of Henley’s loop
(3) volume of blood
(4) Size of organism
Urine concentration is vital for mammals to maintain fluid and electrolyte balance, enabling survival in varying environmental conditions. Among several anatomical and physiological factors influencing this ability, the length of Henle’s loop in the nephron plays a pivotal role.
Overview of Mammalian Urine Concentration
The kidney filters blood, reabsorbing water and important solutes while eliminating waste products in urine. The ability to produce concentrated urine depends on creating an osmotic gradient in the renal medulla, which facilitates water reabsorption from the collecting ducts.
The Nephron and Its Role
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The nephron is the functional unit of the kidney, composed of the renal corpuscle, proximal tubule, loop of Henle, distal tubule, and collecting duct.
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The loop of Henle plays a crucial role in concentrating urine by establishing a countercurrent multiplier system that creates a hyperosmotic medullary interstitium.
Why Length of Henle’s Loop Matters
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Species with longer loops of Henle can create a steeper osmotic gradient, allowing more water reabsorption and more concentrated urine.
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Desert mammals, for example, tend to have very long loops of Henle to conserve water effectively.
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Shorter loops limit the osmotic gradient, resulting in less concentrated urine.
Other Factors and Their Influence
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(1) Glomerulus size: Influences filtration rate but does not directly determine urine concentration.
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(3) Volume of blood: Affects renal perfusion but not the specific concentrating mechanism.
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(4) Size of organism: Larger size often correlates with longer loops, but it’s an indirect effect. The anatomical nephron structure is primary.
Scientific Insights
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Research shows species living in arid environments have evolved longer loops of Henle, enabling maximum urine concentration up to several thousand mOsm/kg.pmc.ncbi.nlm.nih+1
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Aquatic mammals or species in water-abundant environments typically have shorter loops, producing more dilute urine.pmc.ncbi.nlm.nih
Summary Table
Factor Influence on Urine Concentration Glomerulus size Minimal direct effect Length of Henle’s loop Primary determinant of maximum concentration Volume of blood Affects filtration, not concentration Size of organism Indirect correlation via nephron structure Conclusion
Among the options provided, the length of Henle’s loop is the principal factor influencing urine concentration in mammals, as it governs the kidney’s ability to create osmotic gradients necessary for water reabsorption.
Correct Answer: (2) Length of Henley’s loop
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