Elements of Renal Function - McCormick

Question 1

Characteristics of cortical nephrons

Answer 1

Short loops of Henle

Surrounded by peritubular capillaries

Question 2

Characteristics of Juxtamedullary nephrons

Answer 2

Long loops of Henle
Long efferent arterioles are divided into specialized peritubular capillaries - the vasa recta
Functions to concentrate urine

Question 3

Venous drainage of kidney

Answer 3

Interlobular v
Arcuate v
Interlobar v
Renal v

Question 4

What is in charge of filtration?

Answer 4

Glomerular capillaries

High hydrostatic pressure - 60mmHg

Question 5

What is in charge of reabsorption?

Answer 5

Peritubular capillaries
Lower hydrostatic pressure - 13mmHg
Large amts of water and solute reabsorbed

Question 6

Which portion of the kidney receives the most amount of blood?

Answer 6

Cortex - 4-5 L
Outer medulla - .7-1 L
Inner medulla - .2-.25 L

Question 7

What two places do sympathetic neurons synapse on? What is effect?

Answer 7

1. Smooth muscle - afferent arteriolar constriction

2. Granular cells - in afferent arterioles causing renin secretion

Question 8

4 Basic processes of urine formation?

Answer 8

Glomerular filtration - Bowman’s
Tubular Reabsorption - lumen to peritubular cap
Tubular Secretion - peritubular back to lumen
Excretion

Question 9

How to calculate urinary excretion?

Answer 9

Amount filtered - amount reabsorbed + amount secreted

Question 10

If excretion rate is higher than filtration rate?

Answer 10

Tubular secretion must have occurred

And vice versa

Question 11

Filtration rate

Answer 11

Of any freely filtered substance

GFR x plasma concentration of substance

Question 12

Clearance

Answer 12

The volume of plasma from which a substance is completely removed (cleared) by the kidneys in a given period of time
-how effectively the kidneys remove a substance from the bloodstream and excrete it in the urine
Varies

Question 13

How do you calculate the clearance of a substance?

Answer 13

Cx = Ux x V / Px

Question 14

What are the requirements if a compound is used to estimate GFR?

Answer 14

Freely filtered
Not secreted, reabsorbed, produced or degraded by the kidneys
Ex. inulin

Question 15

What is good for monitoring of long term GFR

Answer 15

Pcreatinine

Inversely proportional to GFR

Question 16

A BUN/Cr ratio of > 20/1 indicates?

Answer 16

Preranal
-reduced to renal perfusion due to hypovolemia
BUN reabsorption is increased, sitting around longer so more of it gets taken up

Question 17

BUN/Cr ratio of 10-20/1 indicates?

Answer 17

Normal range or post renal problem

ex. obstruction

Question 18

BUN/Cr ratio of < 10/1 indicates?

Answer 18

Intrarenal problems

Renal damage causes reduced reabsorption of BUN

Question 19

Advantages of using Cystatin C as a marker of GFR?

Answer 19

Continuously made by nucleated cells
Freely filtered
NOT dependent on muscle mass like creatinine

Question 20

PAH clearance estimates?

Answer 20

Estimates renal plasma flow

Question 21

Filtration fraction

Answer 21

The part of renal plasma flow (RPF) that is filtered/diverted into the tubule
Changes with ultrafiltration pressure
Normally ~ 20%

Question 22

How to calculate filtration fraction?

Answer 22

FF = GFR/RPF

Question 23

What happens with an increased FF?

Answer 23

The oncotic pressure of the efferent arteriole increases, facilitating reabsorption of tubular fluid