GFR Flashcards
GFR
- is the rate at which fluid is filtered in the bowman capsule
- in a health male 120ml/min
- 180L/day
- 1 kidney removed GFR decreases 25%
increasing glomerular capillary pressure
- will increase the decreasing GFR
main factor in determining GFR
- glomerular capillary pressure
GLOMERULAR CAPILLARY PRESSURE is proportional to
- GFR
plasma protein oncotic force (oncotic pressure of glomerular capillary)
- promotes reabsorption
- the more concentrated the proteins the greater the force promoting reabsorption
- decrease GFR
diarrhea
vomiting stomach contents
excess sweating
is losing fluid in the body but not protein
- plasma protein concentration increases
- decrease GFR
plasma protein become more concentrated
- decrease GFR
decreasing plasma concentration of protein
- increase GFR
drinking water no protein content
saline infusion
saline induced diuresis (proximal tubule)
- diluting the plasma protein
- increase GFR
oncotic pressure of bowman’s space
- ZERO
- opposing filtration
- does not affect GFR
blocking ureter or urethra with kidney stone
high bladder pressure
post renal failure
- fluid cannot move freely causing pressure in the bowman space
- DECREASE GFR
increase hydrostatic pressure
- increase filtering fluid
in the glomerular capillaries
- filter the fluid but not the protein
- causing an increase in protein concentration
at the end of glomerular capillaries
- filters less fluid due to increase in protein concentration decreasing GFR
in the peritubular capillaries
- more concentrated protein promotes more reabsorption
increase filtration fraction
- increase net force promoting reabsorption
PBC bowman’s capsule pressure
force opposing filtration -
- 8 mm Hg
pyBC
- 0 mm Hg
PGC glomerular capillary pressure
force promoting filtration +
- 45 mm Hg
pyGC
- 24 mm Hg
net filtration formula
creating the GFR of 120ml/min
PGC - pyGC - PBC = 13mm Hg
glomerular capillary
- has a large surface area
filtering membrane (permeable membrane, large surface area)
- capillary endothelial wall with large pores for protein pass thru, has negative pressure reason for not filtering the protein
- glomerular basement membrane, negative charged
- epithelial cell layer of podocytes
negative pressure
- reason for not filtering the protein
damaging the filtering membrane
- will cause proteinuria
- nephrotic syndrome
FREELY filtered by the kidney
major electrolytes
- Na, Cl, K, HCO3
FREELY filtered by the kidney
metabolic waste
- glucose
- amino acid
- ketone bodies
FREELY filtered by the kidney
non natural substance
- inulin
- para-aminohippuric acid PAH
FREELY filtered by the kidney
lower weight proteins and peptides
- insulin
- myoglobin
- CORTISOL
- TESTOSTERONE
NOT freely filtered
- albumin
- plasma protein
- bilirubin
- thyroxine T4
- lipid soluble hormones
- CORTISOL
OSMOLARITY OF THE FILTRATE
- 300 mOsm/L
tubular fluid conc./plasma
TF/P ratio
= 1.0
substance if freely filtered in the bowman capsule
all freely filtered material has a ratio of
- TF/P= 1.0
ratio of .7, .5, .6
- plasma > TF
- no freely filtered
TF/P= 1.2
- TF > plasma
- DISTRACTOR
- IMPOSSIBLE
TF/P=1.0
- FREELY FILTERED
FILTRATION FRACTION
Na, K, Cl, HCO3, glucose
GFR/RPF (renal plasma flow) - GRF= 120 ml/min - RPF= 600ml/min normal ratio = .20 or 20% or 120 ml/min is filtered - 80% is not filtered or 480 ml/min
increase plasma concentration of glucose
- increase filtration >120ml/min
decrease plasma concentration of glucose
- same filtration 120ml/min
glomerular capillary pressure is proportional to
increase GCP
decrease GCP
- GFR
- increase GFR
- decrease GFR
plasma protein concentration is inverse
to GFR
AFFERENT CONSTRICTION
DECREASE
INCREASE
NO CHANGE
- GF pressure - DECREASE
- GFR - DECREASE
- RPF renal plasma flow - DECREASE
- FF - NO CHANGE
EFFERENT CONSTRICTION
- GF pressure -INCREASE
- GFR - INCREASE
- RPF renal plasma flow- DECREASE
- FF -INCREASE
DECREASE OF FLOW in glomerular capillaries
- filter >
SYMPATHETIC stimulation to the kidney
AFFECTS AFFERENT ARTERIOLE MAINLY
- VASOCONSTRICTION of the arterioles
- decrease GFR less fluid absorption
- increase FF
- force promoting reabsorption in the peritubular capillaries INCREASE
KIDNEY HAS NO
- PARASYMPATHETIC STIMULATION
ANGIOTENSIN II
mainly affects EFFERENT ARTERIOLES
- increase renal resistance w/o change in GFR
- affecting afferent no change GCP
- decrease plasma flow
ACE INHIBITOR
dilate EFFERENT ARTERIOLES
- decrease renal resistance
- decrease GFR
- increase renal plasma flow
GFR vs FILTER LOAD
GFR- filtered fluid into bowman capsule
- volume per unit time ML/min
FILTER LOAD- rate of filtering substance into bowman’s capsule MG/min
filtered load
- GFR x plasma concentration of a substance
during PREGNANCY
- INCREASE GFR
- INCREASE FILTER LOAD GLUCOSE (dissolve substance)
- INCREASE PLASMA GLUCOSE CONCENTRATION
- INCREASE ML/MIN causing overload of proximal tubule
- glycosuria is normal in pregnancy
