Introduction to Renal Physiology

Question 1

What part of kidney contains glomeruli and convoluted tubules?

Answer 1

Cortex

Question 2

What part of kidney contains think loops of henle and collecting ducts?

Answer 2

Medulla

Question 3

Salt Conserving Nephron

Answer 3

Juxtamedullary Nephron

Question 4

Salt and Water Wasting Nephron

Answer 4

Cortical Nephron. Used when hydrated

Question 5

Where is primary urine formed?

Answer 5

In glomerulus

Question 6

Can kidney function in gluconeogenesis?

Answer 6

Yes

Question 7

Pain sensation in kidney

Answer 7

Splanchnic nerve originating in renal pelvis.

Question 8

Innervation of kidney?

Answer 8

Sympathetics from celiac and mesenteric plexus. Some parasympathetic innervation, function unclear.

Question 9

Purpose of the glomerulus

Answer 9

Filtration.

Question 10

Concentration of filtrate

Answer 10

Same as concentration of plasma, just lacking large proteins.

Question 11

Hydrostatic pressure and resistance of glomerular capillaries

Answer 11

High pressure, low resistance. Pressure stays constant throughout capillary.

Question 12

Juxtaglomerular apparatus

Answer 12

Distal tubule comes back to own glomerulus and passes next to afferent arteriole. Allows for feedback regulation of afferent tone and GFR. Renin is released from the macula densa.

Question 13

Path of material from blood place to urinary space

Answer 13

Material flows past endothelial cells, through the basement membrane (which acts as a sieve), through slit diaphragms into the slit pore (formed by podocytes), into the urinary space.

Question 14

How does the glomerulus control size and charge of material flowing through filtration barrier?

Answer 14

Barriers are covered in negatively charged proteins.

Question 15

What will flow more freely through the filtration barrier: Cations or Anions? Does size matter?

Answer 15

Cations. Smaller is easier.

Question 16

How is Kf calculated?

Answer 16

Proportional to SA and K (hydraulic conductivity, ease with which water moves across a barrier).

Question 17

Equation for SNGFR

Answer 17

Kf [(Pgc -Pbs - πgc)]. There is no πbs in healthy people.

Question 18

Is GFR determined by blood flow or pressure?

Answer 18

Pressure.

Question 19

What happens to GFR if there’s a kidney stone?

Answer 19

Pbs increases, GFR decreases.

Question 20

What happens to GFR is there’s renal artery stenosis?

Answer 20

Pgc decreases, GFR decreases.

Question 21

Which has a higher Kf: systemic capillary or glomerular capillary? Why?

Answer 21

Glomerular Capillary. Higher hydraulic conductance.

Question 22

Clearance definition and equation

Answer 22

The volume of plasma from which a substance is completely removed per unit time. Provides a way to quantify kidney function.

Cx = (Ux * V)/Px

Where Ux is urine concentration, V is urine flow, Px is plasma concentration.

Question 23

How does clearance relate to GFR

Answer 23

They are equal if the compound is freely absorbed, not reabsorbed or secreted, not broken down, and not synthesized in the kidney.

Question 24

What two markers are used to measure GFR by clearance?

Answer 24

Inulin and Creatinine

Question 25

Equation for amount of substance filtered

Answer 25

Px * GFR

Question 26

Equation to determine amount of compound in urine

Answer 26

UxV = (PxGFR) + TSx - TRx

Amount in urine = amount filtered + amount secreted - amount reabsorbed

Question 27

How can Cx and CCr/Cin relate?

Answer 27

If Cx = CCr, Cx=GFR.
If Cx > CCr, net secretion
If Cx < CCr, net absorption.

Question 28

How is GFR measured clinically?

Answer 28

By measuring plasma creatinine and BUN.

Question 29

What determines how much creatinine is in plasma? Normal plasma creatinine?

Answer 29

Plasma creatinine is inversely proportional to elimination. So, the more excreted, the less plasma creatinine there is. Production is constant, so we don’t have to worry about that. Normal is 0.7 - 1.2 g/dL.

Question 30

What is the BUN value dependent on?

Answer 30

State of hydration.