MCB 246 urinary system Questions With Complete
Solutions
3 Primary Steps in Urine Formation Correct Answers
Glomerular Filtration
Tubular Reabsorption
Tubular Secretion
Aquaporins allow water reabsorption Correct Answers from
hypo-osmotic filtrate into the hyperosmotic medullary interstitial
fluid by osmosis and, thus, both concentrate urine and conserve
water
ascending limb of nephron loop Correct Answers permeable to
NaCl but not water so solution surrounding nephron loop is
more concentrated
Blood Colloid Osmotic Pressure (OPg) Correct Answers
Osmotic pressure from suspended proteins in blood (~32 mm
Hg)
Opposes filtration; tends to draw water out of filtrate into plasma
Capsular Hydrostatic Pressure (HPc) Correct Answers
resistance to flow along nephron and conducting system (~18
mm Hg)
opposes GHP (pushes water and solutes out of filtrate into
plasma)
causes formation of water channels by triggering insertion of
aquaporin proteins in cell membranes of CT and CD (suppressed
by natriuretic factors) Correct Answers ADH
, concentrated filtrate Correct Answers less water and more
solute as the end result
nephron loop creates osmotic gradient (countercurrent multiply)
w 2 different structures in opposite directions
Control of Urine Volume & Osmotic Concentration Correct
Answers Hypothalamus continuously secretes low levels of
ADH - DCT and collecting system are always permeable to
water
At normal ADH levels:
- Collecting system reabsorbs 16.8 liters/day (9.3% of filtrate)
Urine Production in Healthy Adult:
- 1.2 L (0.6% of filtrate) of 800 - 1000 mOsmolar urine per day
Vasa recta balances solute reabsorption & osmosis in medulla
Control of Water Reabsorption Correct Answers Water
reabsorption occurs when the osmotic concentration of
peritubular fluid (out) exceeds that of tubular fluid (in)
Cortical Nephrons Correct Answers 85% of all nephrons
Located mostly within superficial cortex
Nephron loop (loop of Henle) is relatively short
Efferent arteriole delivers blood to a network of peritubular
capillaries
outer
Countercurrent Multiplication Correct Answers process by
which a progressively increasing osmotic gradient is formed in
the interstitial fluid of the renal medulla as a result of
countercurrent flow
Solutions
3 Primary Steps in Urine Formation Correct Answers
Glomerular Filtration
Tubular Reabsorption
Tubular Secretion
Aquaporins allow water reabsorption Correct Answers from
hypo-osmotic filtrate into the hyperosmotic medullary interstitial
fluid by osmosis and, thus, both concentrate urine and conserve
water
ascending limb of nephron loop Correct Answers permeable to
NaCl but not water so solution surrounding nephron loop is
more concentrated
Blood Colloid Osmotic Pressure (OPg) Correct Answers
Osmotic pressure from suspended proteins in blood (~32 mm
Hg)
Opposes filtration; tends to draw water out of filtrate into plasma
Capsular Hydrostatic Pressure (HPc) Correct Answers
resistance to flow along nephron and conducting system (~18
mm Hg)
opposes GHP (pushes water and solutes out of filtrate into
plasma)
causes formation of water channels by triggering insertion of
aquaporin proteins in cell membranes of CT and CD (suppressed
by natriuretic factors) Correct Answers ADH
, concentrated filtrate Correct Answers less water and more
solute as the end result
nephron loop creates osmotic gradient (countercurrent multiply)
w 2 different structures in opposite directions
Control of Urine Volume & Osmotic Concentration Correct
Answers Hypothalamus continuously secretes low levels of
ADH - DCT and collecting system are always permeable to
water
At normal ADH levels:
- Collecting system reabsorbs 16.8 liters/day (9.3% of filtrate)
Urine Production in Healthy Adult:
- 1.2 L (0.6% of filtrate) of 800 - 1000 mOsmolar urine per day
Vasa recta balances solute reabsorption & osmosis in medulla
Control of Water Reabsorption Correct Answers Water
reabsorption occurs when the osmotic concentration of
peritubular fluid (out) exceeds that of tubular fluid (in)
Cortical Nephrons Correct Answers 85% of all nephrons
Located mostly within superficial cortex
Nephron loop (loop of Henle) is relatively short
Efferent arteriole delivers blood to a network of peritubular
capillaries
outer
Countercurrent Multiplication Correct Answers process by
which a progressively increasing osmotic gradient is formed in
the interstitial fluid of the renal medulla as a result of
countercurrent flow
