2026 Advanced pathophysiology: Renal
system physiology and dysfunction with
350 Exam Questions and Correct Answers
Roles of renal system - Answer--concentration of solutes, body volumes, removal of
end-products of metabolism, removal of foreign substances, pH regulation: reserving
bicarbonate and eliminating hydrogen ions
Kidney - Answer--1% body weight, 20-25% cardiac output
Cortex - Answer--outer area
Medulla - Answer--inner area
Nephron - Answer--functional unit
Afferent arteriole - Answer--into glomerulus, short and wide, controls flow by
vasoconstriction. Low resistance input pathway
Efferent arteriole - Answer--out of glomerulus, high resistance outflow pathway
(Efferent arteriole plus vasa recta)
Glomerular (glomerulus) capilllary - Answer--where filtration occurs
Three key processes - Answer--filtration, reabsorption, secretion
Urine - Answer--water and solutes are filtered from the glomerular capillary, filtrate
passes into the renal tubule, reabsorption back into the blood stream occurs, then
secreted back into the renal tubule as urine
Forces that filter fluid out - Answer--glomerular capillary hydrostatic pressure (Pgc)
and Bowman's space oncotic pressure (πBS)
Forces that oppose ultrafiltration - Answer--Bowman's space hydrostatic pressure
(Pbs) and Glomerular capillary oncotic pressure (πGC)
Juxtaglomerular apparatus - Answer--
, Clearance - Answer--volume of blood-borne substances which are removed from the
plasma per unit time by the kidney
Creatinine - Answer--measure of glomerular filtration rate,
Para-amino hippuric acid (PAH) - Answer--measure of renal plasma flow, if PAH is
injected, 100% is extracted from plasma, however it can be secreted. Clear
585ml/min plasma, PAH clearance = 91% of plasma load of PAH entering kidneys
(585/0.91=643 mL/min total plasma flow. (643/(1-0.45))=1169 mL/min (provide
filtration fraction
Fluid reabsorption - Answer--180L/day (urine is 1.5 L/day)
Salt reabsorption - Answer--filter about 1800g/day, urine has about 10g NaCl.
Reabsorption - Answer--we reabsorb > 99% of salt, water and glucose
Proximal tubule - Answer--reabsorb protein, 75% of water and sodium, overall 70%
of stuff is reabsorbed here.
Loop of Henle - Answer--DTL-permeable to H2O, low permeability to salt and urea;
ATL- 0-low H2O permeability, low permeability to urea (enters), permeability to NaCL
Thick AL (Ascending limb?) - Answer--active NaCl, low perm to H2O
Distal tubule/collecting duct - Answer--reabsorption- NaCl, bicarbonate, urea,
potassium, water (under control of the anti-diuretic hormone). Secretion- K+, H+, and
NH3 (ammonia- note diuretics increase urine loss)
K+ secretion - Answer--most K+ is reabsorbed, K is secreted in proximal tubule,
reabsorbed and secreted in distal tubule and collecting duct, K+ secretion is
increased by aldosterone released from adrenal glands
H+ secretion - Answer--active over entire nephron length, mechanisms- reabsorption
of filtered bicarbonate, acid-excretion (phosphate and ammonia)
Renal control of body fluids - Answer--you can easily produce a dilute urine- no ADH,
absorb more solutes than water. Concentrated urine formation requires hyper
osmotic medullary interstitium (loop of Henle), ADH, and the vasa recta
Loop of Henle and the medullary interstitium - Answer--has a standing gradient, must
have fluid movement, concentration gradient along arms is greater than across arms,
works only with asymmetry
system physiology and dysfunction with
350 Exam Questions and Correct Answers
Roles of renal system - Answer--concentration of solutes, body volumes, removal of
end-products of metabolism, removal of foreign substances, pH regulation: reserving
bicarbonate and eliminating hydrogen ions
Kidney - Answer--1% body weight, 20-25% cardiac output
Cortex - Answer--outer area
Medulla - Answer--inner area
Nephron - Answer--functional unit
Afferent arteriole - Answer--into glomerulus, short and wide, controls flow by
vasoconstriction. Low resistance input pathway
Efferent arteriole - Answer--out of glomerulus, high resistance outflow pathway
(Efferent arteriole plus vasa recta)
Glomerular (glomerulus) capilllary - Answer--where filtration occurs
Three key processes - Answer--filtration, reabsorption, secretion
Urine - Answer--water and solutes are filtered from the glomerular capillary, filtrate
passes into the renal tubule, reabsorption back into the blood stream occurs, then
secreted back into the renal tubule as urine
Forces that filter fluid out - Answer--glomerular capillary hydrostatic pressure (Pgc)
and Bowman's space oncotic pressure (πBS)
Forces that oppose ultrafiltration - Answer--Bowman's space hydrostatic pressure
(Pbs) and Glomerular capillary oncotic pressure (πGC)
Juxtaglomerular apparatus - Answer--
, Clearance - Answer--volume of blood-borne substances which are removed from the
plasma per unit time by the kidney
Creatinine - Answer--measure of glomerular filtration rate,
Para-amino hippuric acid (PAH) - Answer--measure of renal plasma flow, if PAH is
injected, 100% is extracted from plasma, however it can be secreted. Clear
585ml/min plasma, PAH clearance = 91% of plasma load of PAH entering kidneys
(585/0.91=643 mL/min total plasma flow. (643/(1-0.45))=1169 mL/min (provide
filtration fraction
Fluid reabsorption - Answer--180L/day (urine is 1.5 L/day)
Salt reabsorption - Answer--filter about 1800g/day, urine has about 10g NaCl.
Reabsorption - Answer--we reabsorb > 99% of salt, water and glucose
Proximal tubule - Answer--reabsorb protein, 75% of water and sodium, overall 70%
of stuff is reabsorbed here.
Loop of Henle - Answer--DTL-permeable to H2O, low permeability to salt and urea;
ATL- 0-low H2O permeability, low permeability to urea (enters), permeability to NaCL
Thick AL (Ascending limb?) - Answer--active NaCl, low perm to H2O
Distal tubule/collecting duct - Answer--reabsorption- NaCl, bicarbonate, urea,
potassium, water (under control of the anti-diuretic hormone). Secretion- K+, H+, and
NH3 (ammonia- note diuretics increase urine loss)
K+ secretion - Answer--most K+ is reabsorbed, K is secreted in proximal tubule,
reabsorbed and secreted in distal tubule and collecting duct, K+ secretion is
increased by aldosterone released from adrenal glands
H+ secretion - Answer--active over entire nephron length, mechanisms- reabsorption
of filtered bicarbonate, acid-excretion (phosphate and ammonia)
Renal control of body fluids - Answer--you can easily produce a dilute urine- no ADH,
absorb more solutes than water. Concentrated urine formation requires hyper
osmotic medullary interstitium (loop of Henle), ADH, and the vasa recta
Loop of Henle and the medullary interstitium - Answer--has a standing gradient, must
have fluid movement, concentration gradient along arms is greater than across arms,
works only with asymmetry
