Mass Balance and Clearance Flashcards
Define Filtration
Movement of water and solutes from glomerulus into Bowman’s space
Define Secretion
Movement of substances from peritubular capillaries to renal tubular lumen
Define Reabsorption
Movement of substances from renal tubular lumen to peritubular capillaries
Define Excretion
Elimination of substances via urination
List the three ways kidneys handle different substances and give an example of each
- Freely filtered and completely secreted (ex. PAH)
- Freely filtered, not reabsorbed or secreted (ex. inulin)
- Freely filtered and completely reabsorbed (ex. glucose, insulin)
Define and give the equation for renal plasma flow (RPF)
Volume of plasma that flows through kidneys per unit time (normal = 600 mL/min)
RPF = VU/(Pa-Pv)
Define renal blood flow (RBF)
Volume of whole blood that flows through kidneys per unit time (normal = 1100 mL/min or 25% of CO)
Define glomerular filtration rate (GFR)
Volume of filtrate that forms at glomerulus per unit time (normal = 120 mL/min)
Define and give the equation for clearance
Volume of plasma from which all of a particular substance has been removed per unit time
C = VU/Px
When does C = GFR?
When a substance is freely filtered, not secreted and not reabsorbed (ex. inulin)
What substance can approximate C = GFR?
Creatinine
Define these general clinical relationships:
Cx > Cinulin
Cx < Cinulin
Net secretion
Net reabsorption
What is the Tm of glucose?
Rate = 400 mg/min
Define and give the equation for filtration fraction (FF)
Ratio of filtrate (GFR) to renal plasma flow (RPF)
FF = (GFR/RPF) * 100
Define and give the equation for filtered load (FL)
Amount of a substance filtered per unit time
FL = GFR * Px
