S2 Bsf Exam 4: Glomerular Filtration

Front 1

Main functions of kidney

Back 1

filtration (from blood to Bowman's space)
secretion (from interstital space to lumen)
reabsorption (from lumen to interstitual space)
excretion (from lumen out of body)

Front 2

Nephrons function independently before merging to form ___________

In what part of the nephron does filtration occur?
(rest reabsorbs & secretes solutes & water)

Back 2

cortical collecting tubule (CCT)


renal corpuscle

Front 3

List the parts of the renal corpuscle

Back 3

glomerulus= capillary bed
Bowman's space= continuity of tubule (lumen) into corpuscle
Bowman's capsule= surrounds Bowman's space & glomerulus

Front 4

(passive) Filtration FAVORS what type of molecules

Back 4

MW< 5.5 kDa solutes
cations
flexible molecules

Front 5

(passive) filtration RESTRICTS what type of molecules

Back 5

MW> 69 kDa solutes
anions
rigid or globular shaped moelcules

(neutral & MW 14-69 kDA are variably restricted)

Front 6

Describe the 3 filtration barriers
(least--> most restrictive)

Back 6

1. Endothelial fenestrations
-restrict cells only
-neg charge, repulses large neg molecuels
2. Basement membrane
-restrict medium to large molecules
-neg charge (heparin sulfate), restricts anions
3. Podacytes
-restricts small molecules
-neg slit diaphram w/ 7-14 nm slits, restricts neg

Front 7

The basement membrane is discontinuous at the _________________

What happens when immune complexes enter through this space & accumulate?

Back 7

capillary-mesangial cell jxn

immune-complex glomerular disease--> inflammatory response-->cell death, scarring, renal corpuscle death

Front 8

What are the 2 main proteins that form the negatively charged slit diaphragm?


what do common symptoms do mutations lead to?

Back 8

nephrin & podocin



proteinuria (focal segmental glomerulosclerosis)

Front 9

If the filtration barriers of the glomerulus are working what should NOT be in the urine w/i Bowman's space?

Back 9

protein
cellular elements (RBC, WBC, platelets)
salts, organic molecules

Front 10

What is the Glomerular Filtration Rate (GFR)?

Back 10

the amount of fluid filtered by BOTH kidneys at any GIVEN TIME

(normal GFR= (125 mL/min) / 1.73 m^2)
(110 mL/min for females)

Front 11

GFR is determined by ______________


Give the equation

Back 11

net starling forces

GFR=Kf * PUF
(kf= ultrafiltration coefficient, PUF= net filtration pressure)

Front 12

How can PUF (net filtration pressure) be calculated?

Back 12

PUF= [PGC-PBS)-(nGC-nBS)

PGC & PBS= glomerular capillary & Bowman's space hydrostatic pressure
nGC & NBS= " " oncotic pressure

Front 13

How can Kf (ultrafiltration/reflection coefficient) be calculated?

Back 13

Kf= hydraulic conductivity * filtration surface area


(Kfkidney= 4.2 mL/min/mm Hg for 100g of kidney)

Front 14

How might Kf be altered?

Back 14

mesangial cells (respond to PTH, ANG II, AVP) contract--> decreases filtration surface area

Front 15

________ & ________oppose movement into Bowman's space (ultrafiltration)

Back 15

PBS (Bowman's space hydrostatic pressure) &
nGC (glomerular capillary oncotic pressure

Front 16

Thus _________ & ________ filter fluid (water) out of Glomerulus into Bowman's space

Back 16

PGC (glomerular capillary hydrostatic pressure) &
nBS (Bowman's space oncotic pressure)

Front 17

How is Renal Plasma Flow Rate (RPF) calculated?



RPF is (high/low) in the kidney

Back 17

RPF= RBF * (1- hematocrit)

(RBF=renal blood flow rate, normal=1L/min, 20% CO)

high (normal= 600 mL/min)

Front 18

The kidney has 1 input _____________
& 2 outputs __________ & ___________

Back 18

input: renal artery
outputs: renal vein & urine

Front 19

The renal capsules has 1 input___________
& 1 output ___________

Back 19

input: afferent arteriole
output: efferent arteriole

(filtered: glomerulus-->Bowman's space)

Front 20

______, _______, & ______ are constant across the glomerulus capillary bed


_______ increases

Back 20

PGC, PBS, & nBS (constant)



nGC (increases)

Front 21

Since nGC increases, ____ decrease


Where is equilibrium (nGC= PGC) reached?

Back 21

PUF


efferent arteriole

Front 22

How can RBF & GFR be altered?

Back 22

by independently modifying resistance in the afferent & efferent arterioles


(afferent usually relatively lower--> PGC high)

Front 23

Increased resistance in the AFFERENT arteriole leads to _____ PCG & RPF, thus __________ GFR

Back 23

decreased PGC & RPF, thus decreasing GFR

Front 24

Increased resistance in the EFFERENT arterioles leads to _________PGC dominates which initially ________ GFR, then ___________RPF dominates & GFR_________

Back 24

increased PGC dominates & GFR increases

then decreased RPF dominates & GFR decreases

Front 25

Filtered fraction (FF)=GFR/RPF,
thus as RPF increases, a (smaller/larger) fraction of RPF is filtered

Back 25

smaller fraction


*(in normal kidney, changes in fractions are minimal, FF= 0.20)

Front 26

The peritubular & Vasa recta capillaries play a role in reabsorption & delivery of O2 & nutrients, thus they favor (secretion/absorption)

Back 26

favor absorption

(PPC low, nPC high)

Front 27

How is arterial input of X calculated?

Back 27

X= Pxa * RPFa

Pxa= plasma concentration of X in renal artery
RPFa= renal plasma flow rate

(venous output calc same, use plasma conc in renal vein (Pxv), & renal vein flow rate (RPFv) instead)

Front 28

How is urine output of X calculated?

Back 28

X= Ux * V.

Ux= urine concentration X
V.= urine flow rate

Front 29

the Clearance of X (Cx) = ___________ /_________

Back 29

Cx= (Ux*V.)/ Pxa
(= urine output X / plasma concentration X in renal artery)

excretion rate of X (mg/min) / [X]in plasma (mg/min)

Front 30

If substance X is freely filterable (X in ultrafiltrate= X in plasma), Cx = _________


What substances are freely filterable?

Back 30

Cx = GFR



Creatinine* & inulin

Front 31

GFR= (1 mg/dL / Pcreatinine) * GFR normal

Normal GFR= ?

Back 31

125 mL/min = 180 mL/day

Front 32

The ratio of plasma BUN : plasma creatinine can be used as an indicator of __________________

Back 32

kidney function

(normal is 10-20:1)

Front 33

> 20:1 indicates what?

Back 33

increased BUN reabsorption


(dehydration, congestive heart failure, kidney failure, shock)

Front 34

<10:1 indicates what?

Back 34

decreased BUN reabsorption


(liver damage, malnutrition, over hydration)

Front 35

clearance of ______ is used to measure RPF
(bc it is cleared completely)


what is the equation for RPF?

Back 35

PAH


RPF= CPAH= (UPAH * V.) / PPAHa

Front 36

Filtered load (FL) is the rate that X (freely filtered substance) enters the Bowman's space.
How is FL calculated?

Back 36

FL= Px * GFR

Front 37

Fraction Excretion (FE) is the fraction of filtered solute X excreted in urine.
How is FE calculated?

Back 37

FE= (Ux * V.) / (Pax * GFR)