Mass Balance And Clearance

Question 1

There are three basic processes that determine composition and volume of urine

Answer 1

Filtration
Secretion
Reabsorption

Question 2

Excretion

Answer 2

Excretion = urine flow rate x [X]urine
Excretion = FL + secretion - reabsorption

Question 3

Tubular load

Answer 3

TLx = tubular fluid flow x [X]
TL = FL + secretion

Question 4

Filtration load

Answer 4

FL = GFR * [X]plasma

Question 5

Secretion

Answer 5

Active transport of substances from interstitial fluid through the cells into the tubular fluid

Question 6

Transport

Answer 6

Either secretion (excretion > FL) or reabsorption (excretion < FL)
Positive transport is secretion, negative is reabsorption

Question 7

Filtration barrrier

Answer 7

Endothelial cells, basement membrane, and podocytes fluids and solutes must pass through
Negative charge of endothelial cell surface repel passage or large anion proteins
Podocytes have small filtration slits

Question 8

Total resistance to blood flow through the kidney

Answer 8

50% afferent arteriole
35% efferent arteriole
15% Remainder of vessels

Question 9

Net filtration pressure

Answer 9

Constrict afferent: inc resistance, dec Pcc GFR and RBF
Constrict efferent: inc restistance Pcc and GFR, dec RBF
Dilate efferent: dec resistance Pcc and GFR, inc RBF
Dilate afferent: inc Pcc GFR and RBF, dec resistance

Question 10

Quick and dirty osmolarity

Answer 10

Uosm&raquo_space; Osm plasma (negative CH2O)
Plasma osmolarity high, should be negative CH2O
Low, should be positive

Uosm &laquo_space;Osm plasma (positive CH2O)
Plasma low, Uosm should be low

Question 11

Measure GFR

Answer 11

GFR = creatinine clearance

Normally 100

Question 11

RPF

Answer 11

RPF = PAH clearance

Excretion = quantity delivered in renal plasma