Re-Absorption & Secretion In Distal Tubule

RE-ABSORPTION & SECRETION IN DISTAL TUBULE

Q. 1

Active resorption of sodium ion occurs in:

March 2008

 A

Ascending loop of henle

 B

Early distal tubule

 C

Proximal tubule

 D

All of the above

Q. 1

Active resorption of sodium ion occurs in:

March 2008

 A

Ascending loop of henle

 B

Early distal tubule

 C

Proximal tubule

 D

All of the above

Ans. D

Explanation:

Ans. D: All of the above

About 65% of the filtered electrolytes are absorbed in PCT actively Thin ascending loop of Henle: Passive diffusion of sodium

Thick ascending loop of Henle: Active transportation of sodium

Early distal tubule: Similar properties as that of thick ascending loop of Henle


Q. 2

Aldosterone acts chiefly on which of the following cells: 

September 2011

 A

DCT

 B

PCT

 C

Loop of Henle

 D

Glomerulus

Q. 2

Aldosterone acts chiefly on which of the following cells: 

September 2011

 A

DCT

 B

PCT

 C

Loop of Henle

 D

Glomerulus

Ans. A

Explanation:

Ans. A: DCT

Aldosterone acts on the principal (P) cells of DCT and collecting tubules

Aldosterone

  • It increases the reabsorption of sodium ions and water and the secretion of potassium ions in the collecting ducts and distal convoluted tubule of the kidneys’ functional unit, the nephron.
  • This increases blood volume and, therefore, increases blood pressure.
  • Drugs that interfere with the secretion or action of aldosterone are in use as antihypertensives.
  • One example is spironolactone, which lowers blood pressure by blocking the aldosterone receptor.
  • Aldosterone is part of the renin-angiotensin system.
  • Aldosterone is a yellow steroid hormone (mineralocorticoid family) produced by the outer-section (zona glomerulosa) of the adrenal cortex.
  • The overall effect of aldosterone is to increase reabsorption of ions and water in the kidney. Its activity is reduced in Addison’s disease and increased in Conn’s syndrome.

Q. 3

Which part of collecting duct is functionally similar to the later segment of distal tubule?

 A

Cortical part of collecting duct.

 B

Thin ascending part of collecting duct.

 C

Thick ascending part of collecting duct.

 D

Medullary part collecting duct.

Q. 3

Which part of collecting duct is functionally similar to the later segment of distal tubule?

 A

Cortical part of collecting duct.

 B

Thin ascending part of collecting duct.

 C

Thick ascending part of collecting duct.

 D

Medullary part collecting duct.

Ans. A

Explanation:

Cortical part of collecting duct.

REABSORPTION IN LATE DISTAL TUBULE:

  • Functionally similar to cortical collecting tubule.
  • Facultative type:
    • Reabsorption of solutes/water depends on water/electrolyte balance.
    • Hence, “Facultative type” of absorption.
  • Cells involved in reabsoprtion:
    • Principal (P) cells.
    • Intercalated (I) cells



Q. 4

What are the major functions of “I” cells?

 A

Reabsorb potassium ion.

 B

Secrete potassium ion.

 C

Excrete potassium ion.

 D

All of the above 

Q. 4

What are the major functions of “I” cells?

 A

Reabsorb potassium ion.

 B

Secrete potassium ion.

 C

Excrete potassium ion.

 D

All of the above 

Ans. A

Explanation:

Reabsorb potassium ion.

REABSORPTION IN LATE DISTAL TUBULE:

  • Functionally similar to cortical collecting tubule.
  • Facultative type:
    • Reabsorption of solutes/water depends on water/electrolyte balance.
    • Hence, “Facultative type” of absorption.
  • Cells involved in reabsoprtion:
    • Principal (P) cells.
    • Intercalated (I) cells.

FUNCTIONS OF ‘I’ CELLS:

  • Reabsorb potassium ion.
  • Secrete hydrogen ions into tubular lumen.


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