TRC: Distal tubule

Distal tubule

The distal tubule is involved in reabsorption of water, Na⁺ and Ca²⁺ ions. H⁺, NH4⁺, creatinine and drugs are actively secreted by this part of the renal tubule. Na+ions are resorbed via co-transport together with Cl- ions and via active transport of the Na⁺/K⁺-ATPase pump.

Aldosterone controls the exchange of Na⁺/K⁺ions. Water is reabsorbed via osmosis; this process is regulated by the pituitary hormone ADH. Ca²⁺ ions are resorbed by carrier-mediated transport, which is controlled by the parathyroid hormone (PTH). H⁺ ions are secreted via a process of countertransport with Na⁺ ions.

Which of the following factors does NOT increase potassium excretion?

Option explanation:

avid sodium re-absorption

excess poorly absorbed anions.like ketons and phosphates

a rise in intra tubular potassium e.g. alkalosis

a fall in intracellular potassium e.g. acidosis

I Thiazide diuretics’ site of action is the distal tubule

II Thiazide diuretics are weaker than loop diuretics

Option explanation:

I is true, II is true

I is true, II is false

I is false, II is true

I is false, II is false

Distal tubule

Distal tubule

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