Overview of Renal Physiology

Question 1

What are the RBF, RPF, FF, GFR, and what are typical values for each?

Answer 1

Renal Blood Flow, Renal Plasma Flow, Filtration Factor, and Glomerular Filtration Rate. RBF = 25% of CO (.25 x 5.2 = 1.3L), RPF = 50% of RBF (.50 x 1.3L = 650ml), GFR = 20% of RPF (.20 x 650ml = 130ml/min)

Question 2

What is the typical volume of plasma filtered per day and urine produced per day and what does this imply?

Answer 2

190L of plasma are filtered each day, with 1.5L of urine produced, thus 188.5L of plasma are reabsorbed. The kidneys use about 10% of the body’s total energy each day.

Question 3

Summarize the Renin-Angiotensin system including where the factors are made, what triggers their release, and what their function is.

Answer 3

Angiotensinogen made by liver (13AA), Renin secreted by juxtaglomerular cells, controlled by baroreceptors in response to low MAP, cleaves angiotensinogen to angiotensin I (10AA), ACE converts Ang I to Ang II (8AA), Ang IIConstricts vascular smooth muscle (Inc SVR) Efferent Arterioles>Afferent Arterioles (Inc GFR), Inc MAP.

Question 4

What are the typical plasma fluid volumes in a 70kg individual?

Answer 4

Intracellular = 27L total, 24L non-circulating cells, 3L RBC. Extracellular Fluid = 15L total, 12L Interstitial fluid, 3L Plasma.