Kidney Lecture 2: The Tubule

Question 1

What can only pass through the tubules?

Answer 1

Only plasma (this is blood - haematocrit) can pass through the glomeruli structures

Question 2

Normal GFR?

Answer 2

120ml/min

180 L/d

Question 3

Proximal Tubule

Answer 3

Confined to renal cortex

Active reabsorption of multiple things- amino acids, glucose, bicarbonate, phosphate, salt and water, K+, Cl- and urate

Metabolically active cells

Question 4

Loop of Henle

Answer 4

Generates medullary conc grad via countercurrent system

Active Na reabsorption in thick ascending limb
Thick ascending limb is permeable to water

Development of a hypertonic interstitium in the medullary regions of the kidney

Production of a dilute (hypo-osmotic) filtrate entering the distal tubule

Question 5

Distal convoluted tubule

Answer 5

Distal tubule and cortical collecting ducts allow fine tuning of Na reabsorption, K+ and acid base balance

Impermeable to passive movement of water and Na

Uses NCCT cotransprter to re absorb 5% of Na

Specific epithelial channel absorbs Ca2+, paracellular route Ca2+ and Mg2+

Hypoalkaemia due to increased delivery of Na due to increased delivery of Na to collecting duct

Question 6

Collecting duct

Answer 6

Mediated water absorption and maintains acid homeostasis

Principal cells- Na and water reabsorption and K excretion
-ENaC- specific Na transporter, main site of Na regulation
-Aldosterone- increases the number of open ENaC channels regulating Na absorption

Intercalated cells (alpha and beta) secrete H or HCO3
-essential for acid base homeostasis

Question 7

Diuretics at proximal tubule

Answer 7

Carbonic anhydrase inhibitors- acetazolamide

Question 8

Loop diuretics

Answer 8

Affects the Na/K/Cl channel

Furosemide

Question 9

Distal convoluted tubule

Answer 9

At the Na/Cl channels

Thiazide diuretics

Question 10

Diuretics at collecting duct

Answer 10

K sparing diuretics

Affects Mineralocorticoid receptors or Na K H channel

Spironolactone