Nephron Function and Filtration

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Questions and Answers

How would drastically reducing the number of nephrons in both kidneys impact blood filtration, assuming the remaining nephrons function at a normal rate?

  • The filtration rate would decrease, potentially leading to waste buildup in the blood. (correct)
  • The filtration rate would remain the same as the body only needs one million nephrons.
  • The filtration rate would initially decrease but quickly recover to normal levels due to kidney regeneration.
  • The filtration rate would increase proportionally to compensate for the loss.

If a patient's proximal convoluted tubule is damaged, what immediate effect would this have on glucose levels in the urine?

  • Only a slight change would occur, as the collecting duct can compensate by reabsorbing the excess glucose.
  • Glucose levels in the urine would decrease due to increased reabsorption in other nephron segments.
  • Glucose levels in the urine would significantly increase as the proximal tubule is responsible for all reabsorption. (correct)
  • There would be no change in glucose levels, as glucose is primarily reabsorbed in the loop of Henle.

How does the length of the loop of Henle correlate with urine concentration, and what implications does this have for animals in different environments?

  • Longer loops of Henle result in more concentrated urine, which is advantageous for animals in arid environments. (correct)
  • Longer loops of Henle result in less concentrated urine, as more water is excreted.
  • Shorter loops of Henle result in more concentrated urine, which is advantageous for animals in aquatic environments.
  • The length of the loop of Henle has no significant impact on urine concentration.

If the average daily urine output is 1.8 liters, what percentage of the initial filtrate volume is reabsorbed back into the bloodstream by the nephrons?

<p>99% (A)</p> Signup and view all the answers

In a patient with diabetes experiencing hyperglycemia, how does excess glucose in the filtrate affect urine volume, and why?

<p>Urine volume increases because glucose in the filtrate increases its osmolarity, pulling more water into the urine. (B)</p> Signup and view all the answers

If a drug inhibits the reabsorption of sodium chloride in the ascending limb of the loop of Henle, what direct effect would this have on the osmolarity of the medullary interstitium?

<p>The osmolarity of the medullary interstitium would decrease as less sodium chloride is reabsorbed. (B)</p> Signup and view all the answers

If the secretion of hydrogen ions in the distal convoluted tubule is impaired, how would this directly affect blood pH?

<p>Blood pH would decrease, leading to acidosis. (B)</p> Signup and view all the answers

In a patient experiencing kidney failure, what changes in the secretion of creatinine would be expected, and how would this affect its concentration in the blood?

<p>Creatinine secretion would decrease, leading to increased levels in the blood. (D)</p> Signup and view all the answers

How would a significant reduction in the reabsorption of bicarbonate in the proximal convoluted tubule most likely affect acid-base balance in the body?

<p>It would lead to metabolic acidosis due to increased excretion of bicarbonate. (D)</p> Signup and view all the answers

If a patient's collecting ducts become impermeable to water due to a condition like nephrogenic diabetes insipidus, what would be the direct result on urine volume and concentration?

<p>Urine volume would increase, and urine concentration would decrease. (B)</p> Signup and view all the answers

Flashcards

Nephrons

Filtration subunits within the kidneys, numbering about one million per kidney.

Glomerulus

Capillary bed within the nephron that filters blood into the nephron tubules.

Reabsorption

Process where 99% of filtered substances are returned to the bloodstream.

65% Reabsorption

The percentage of filtered substances reabsorbed in the proximal convoluted tubule.

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18 Liters/Day

If reabsorption is reduced by 10%, how much urine would be excreted daily?

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Proximal Tubule

Location where 100% of filtered glucose is reabsorbed.

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Thin Descending Limb

Section of the nephron where only water is reabsorbed, concentrating the urine.

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Secretion

Moving substances from the blood into the nephron tubules for excretion.

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Thin Descending Limb

The location in the nephron where urea is secreted.

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Filtration, Reabsorption, Secretion

Overall processes in nephrons to produce urine.

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Study Notes

  • Nephrons are the filtration subunits within the kidneys
  • Each kidney has about a million nephrons, totaling two million in the body
  • The body effectively needs only one million nephrons to function properly

Blood Filtration

  • Blood enters the nephron through the afferent arteriole and flows into the glomerulus
  • The glomerulus is a capillary bed that filters blood into the nephron tubules
  • Approximately 120 milliliters of blood are filtered per minute, totaling about 180 liters per day

Reabsorption Process

  • Only 1% of the filtered fluid becomes urine, about 1.8 liters per day
  • 99% of the filtered substances are reabsorbed back into the bloodstream via peritubular capillaries
  • Reabsorption is essential for maintaining proper concentration of ions, amino acids, glucose, and urea in the body
  • The filtrate passes through the glomerular capsule, proximal convoluted tubule, descending limb of the loop of Henle, ascending limb of the loop of Henle, distal convoluted tubule, and collecting duct

Reabsorption Percentages in Different Tubule Areas

  • Proximal convoluted tubule: 65% of filtered substances are reabsorbed
  • Loop of Henle: 15% of filtered substances are reabsorbed
  • Distal convoluted tubule: 15% of filtered substances are reabsorbed
  • Collecting duct: 5% of filtered substances are reabsorbed

Consequences of Altered Reabsorption

  • A 10% reduction in reabsorption across all tubule areas would lead to the excretion of 18 liters of urine per day
  • Excreting 18 liters of urine daily is unsustainable and would be fatal

Substances Reabsorbed at the Proximal Convoluted Tubule

  • Ions: sodium, potassium, chloride, calcium, magnesium
  • Bicarbonate, water, amino acids, urea, and glucose

Glucose Reabsorption

  • The proximal convoluted tubule is the only site where 100% of filtered glucose is reabsorbed
  • If too much glucose is filtered, it cannot all be reabsorbed, leading to glucose in the urine
  • Glucose has a strong osmolarity, pulling water with it, which increases urine volume in diabetics

Thin Descending Limb of the Loop of Henle

  • Only water is reabsorbed in this section
  • Longer loops of Henle allow for more water reabsorption, concentrating the urine
  • Desert-dwelling animals have long loops of Henle to maximize water reabsorption

Thick Ascending Limb of the Loop of Henle

  • Ions (sodium, potassium, chloride, calcium, magnesium) and bicarbonate are reabsorbed

Distal Convoluted Tubule

  • Ions, bicarbonate, and water are reabsorbed

Collecting Duct

  • Sodium chloride, bicarbonate, water, and urea are reabsorbed

Secretion

  • Secretion involves moving substances from the blood into the nephron tubules for excretion
  • In the proximal convoluted tubule, urea, uric acid, creatinine, hydrogen ions, drugs, and ammonia are secreted
  • Urea is secreted in the Thin Descending Limb of the loop of Henle
  • In the distal convoluted tubule hydrogen ions, some drugs, and ammonia are secreted

Summary of Filtration, Reabsorption, and Secretion

  • Most substances are filtered into the tubules
  • Nearly 100% of the filtered substances are reabsorbed back into the body
  • Specific products are secreted back into the tubules for excretion, resulting in only 1% of the filtered volume being excreted as urine

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