Renal Physiology

Question 1

Which marker/s may be used to evaluate or estimate the plasma volume?

a. inulin
b. deuterium oxide
c. radioactive iodinated serum albumin
d. mannitol
e. NOTA

Answer 1

C. radioactive iodinated serum albumin (RISA)

Total Body Water (TBW)
> tritium oxide, deuterium oxide, antipyrine

Extracellular Fluid Compartment (ECF)
> sulfate, inulin, mannitol

Plasma
> RISA, evans blue

Interstitial Fluid = ECF - Plasma
ICF = TBW - ECF

Question 2

Infusion of isotonic NaCl will cause:

a. increase in ECF osmolarity
b. increase in ICF osmolarity
c. increase in ECF volume
d. increase in ICF volume
e. B and D

Answer 2

C. increase in ECF volume

Since the infused NaCl solution is isotonic, there will be no movement of water (osmosis). Hence, ECF and ICF osmolarity will not change. Only ECF volume will increase.

Review how to predict free water movement in various scenarios (page 71).

Question 3

Recite the formula for plasma osmolarity.

Answer 3

Posm = 2 x Na + glucose/18 + BUN/2.8

where
Posm = plasma osmolarity (mOsm/L)
Na = concentration (mEq/L)
glucose = concentration (mg/dL)
BUN = concentration (mg/dL)

Question 4

True of juxtamedullary nephrons

a. comprise 75% of nephrons
b. has longer loops of Henle
c. with peritubular capillaries
d. AOTA
e. NOTA

Answer 4

B. has longer loops of Henle

juxtamedullary nephrons

• located in the corticomedullary junction
• comprise 25% of nephrons
• has SHORTER loops of Henle
• with vasa recta

Question 5

Identify the other name of the renal corpuscle.

Answer 5

Malphigian corpuscle

There are two structures named Malphigian corpuscle.

(1) Renal corpuscles
(2) Splenic white pulp / lymphoid nodules / white nodules

Question 6

TRUE or FALSE: The capillary endothelium of the glomerulus is permeable to albumin.

Answer 6

TRUE

Albumin measures around 6 nm in diameter while the endothelium pore measures around 8 nm. What hinders filtration is the negative charge of the BASEMENT MEMBRANE.

Question 7

Most of the excess acids are reabsorbed in what part of the nephron?

a. proximal convoluted tubule
b. descending limb
c. thin ascending limb
d. thick ascending limb
e. distal tubule
f. collecting duct

Answer 7

A. PCT

PCT

• workhorse of the nephron
• absorbs 66% of Na, K, H2O
• absorbs 100% of glucose and most amino acids
• absorbs most of excess acids

Question 8

Furosemide acts on what part of the nephron?

a. proximal convoluted tubule
b. descending limb
c. thin ascending limb
d. thick ascending limb
e. distal tubule
f. collecting duct

Answer 8

D. thick ascending limb

Furosemide is a loop diuretic. Loop diuretics inhibit the luminal Na-K-Cl cotransporter in the thick ascending limb causing sodium, chloride, and potassium loss in the urine.

Question 9

Recite the formula for clearance of a substance.

Answer 9

C = UV / P

C = clearance rate of substance (mL/min)
U = urine concentration of substance (mg/mL)
V = urine flow rate (mL/min)
P = plasma concentration of substance (mg/mL)

Rewrite this and try to cancel values / derive the formula.

Question 10

Which of the following is/are true?

a. If a substance has high clearance, most will be found in the urine.
b. Para-aminohippuric acid has higher clearance than creatinine
c. Inulin is not reabsorbed.
d. Creatinine clearance is a marker of kidney function.
e. AOTA
f. NOTA

Answer 10

E. AOTA

Question 11

Which of the following decreases renal blood flow to the glomerulus?

a. PGE2
b. bradykinin
c. NO
d. angiotensin II
e. ANP

Answer 11

D. angiotensin II

Decreases RBF

• AT2
• sympathetic NS

Question 12

NSAIDs

a. dilate the afferent arteriole
b. dilate the efferent arteriole
c. constrict the afferent arteriole
d. constrict the efferent arteriole
e. NOTA

Answer 12

C. constrict the AFFERENT arteriole

Hence, NSAIDs cause a decrease in renal blood flow and causes primarily a PRERENAL type of AZOTEMIA.

Question 13

Recite the formula of filtration fraction.

Answer 13

FF = GFR / RPF

FF = filtration fraction
GFR = glomerular filtration rate (mL/min)
RPF = renal plasma flow (mL/min)

Question 14

Which of the following will increase GFR?

a. mildly constrict afferent
b. mildly constrict efferent
c. increase plasma protein
d. increase filtration coefficient
e. decrease glomerular hydrostatic pressure

Answer 14

B and D

B. Constriction of the EFFERENT arteriole will cause an increase in glomerular hydrostatic pressure.
D. Increased filtration coefficient will increase filtration due to increased permeability.

Review Starling forces.

Question 15

SEVERE vasoconstriction of the efferent arteriole will cause a decrease in GFR due to what two principles?

Answer 15

(1) increased glomerular ONCOTIC pressure due to trapped albumin in the glomerulus
(2) influx of positively-charged sodium ions (and subsequently water) inside the glomerulus due to the negatively-charged albumin trapped inside

Question 16

The influx of positively-charged sodium ions inside the glomerulus due to the negatively-charged albumin trapped inside is also called:

Answer 16

Gibbs-Donnan effect

This is the behavior of charged particles (e.g. sodium) near a semi-permeable membrane (glomerular membrane) that sometimes fail to distribute evenly across the two sides of the membrane due to the presence of a different charged substance (albumin) that is unable to pass through the membrane.