Nephron Function: Reabsorption Mechanisms
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Questions and Answers

Values below 1.0 indicate that the substance is reabsorbed more avidly than ______.

water

The ______ of Henle is divided into thin descending and thick ascending segments.

loop

The distal tubule is a ______ segment.

diluting

Thiazide diuretics act on the ______ tubule.

<p>distal</p> Signup and view all the answers

Principal cells in the late distal tubule and cortical collecting tubule ______ sodium and secrete potassium.

<p>reabsorb</p> Signup and view all the answers

Potassium-sparing diuretics act on ______ cells.

<p>principal</p> Signup and view all the answers

Intercalated cells ______ hydrogen ions and reabsorb bicarbonate and potassium ions.

<p>avidly secrete</p> Signup and view all the answers

The medullary collecting duct reabsorbs only ______% of the filtered water and sodium.

<p>10</p> Signup and view all the answers

The permeability of the medullary collecting duct to water is ______ dependent.

<p>ADH</p> Signup and view all the answers

The medullary collecting duct is capable of ______ H ions and plays a key role in acid-base regulation.

<p>secreting</p> Signup and view all the answers

Study Notes

Reabsorption Mechanisms

  • Reabsorption of chloride, urea, and other solutes occurs through passive diffusion, coupled with sodium reabsorption
  • 65% of filtered sodium, chloride, bicarbonate, and potassium, and essentially all filtered glucose and amino acids are reabsorbed by the proximal tubule

Proximal Tubule

  • Reabsorbs 65% of filtered sodium, chloride, bicarbonate, and potassium, and essentially all filtered glucose and amino acids
  • Concentrations of solutes along the proximal tubule can be seen in fig 7
  • Secretes organic acids and bases

Loop of Henle

  • Composed of three functionally distinct segments: thin descending segment, thin ascending segment, and thick ascending segment
  • Thick ascending segment reabsorbs sodium, chloride, and potassium (fig 8-B)

Active Transport

  • Primary active transport linked to hydrolysis of ATP (fig 2)
  • Secondary active reabsorption through the tubular membrane (fig 3)
  • Secondary active secretion into the tubules (fig 3)
  • Pinocytosis: an active transport mechanism for reabsorption of proteins
  • Transport maximum for substances that are actively reabsorbed (fig 4)

Distal Tubule and Collecting Duct

  • Forms part of the juxtaglomerular apparatus (JGA)
  • Diluting segment
  • Site of action of thiazide diuretics
  • Principal cells reabsorb sodium and secrete potassium (fig 10)
  • Intercalated cells avidly secrete hydrogen and reabsorb bicarbonate and potassium ions
  • Medullary collecting duct reabsorbs only 10% of filtered water and sodium, permeability to water is ADH dependent

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Description

Understand how the nephron reabsorbs chloride, urea, and other solutes, including the role of passive diffusion and the proximal tubule. Learn about the mechanisms of reabsorption and secretion along different parts of the nephron.

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