10 Questions
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.
distal
Principal cells in the late distal tubule and cortical collecting tubule ______ sodium and secrete potassium.
reabsorb
Potassium-sparing diuretics act on ______ cells.
principal
Intercalated cells ______ hydrogen ions and reabsorb bicarbonate and potassium ions.
avidly secrete
The medullary collecting duct reabsorbs only ______% of the filtered water and sodium.
10
The permeability of the medullary collecting duct to water is ______ dependent.
ADH
The medullary collecting duct is capable of ______ H ions and plays a key role in acid-base regulation.
secreting
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
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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