renal 4 - reabsorption, secretion, clearance Flashcards
which substances are only filtered
inulin and creatinine* (slightly different, creatinine is very slightly secreted)
which substances are filtered and partially reabsorbed
electrolytes (Na, K)
which substances are filtered and completely reabsorbed
glucose, amino acids
which substances are filtered and completely secreted
organic acids (PAH, para-amino hippuric-acid) and bases
what is inulin and where is it found
polysaccharide found in fruits and veggies
which substances are completely or almost completely reabsorbed
water sodium (99%) glucose (100%)
is glucose physiologically regulated
no (not fine tuned hormonally)
is water physiologically regulated
yes (fine tuned hormonally)
is sodium physiologically regulated
yes (fine tuned hormonally)
how is reabsorption mediated (LUMEN INTO CAPILLARY)
which is major and minor
mediated transport (transepithelial)MAJOR diffusion across tight junction (paracellular)MINOR
how does sodium get across the luminal/apical side
how
passive diffusion
high [Na+] in lumen vs cell
depends on area
counter transport, cotransport (prox. con, tub)
diffusion via Na+ channel CCD
how does sodium get across the basolateral side
how
active transport by Na/K ATPase
how does sodium get across the luminal/apical side in the proximal convoluted tubule
cotransport
passive
how does sodium get across the luminal/apical side in the cortical collecting duct
diffusion via Na channel
how does sodium get across the basolateral side in the proximal convoluted tubule
na k atp pump active
how does sodium get across the interstitial fluid into the blood plasma
diffusion and bulk transport
how does sodium get across the filtrate and into the interstitial fluid plasma
mediated transport
diffusion then na k atp ase
what is the clearance of glucose
zero b/c non is voided in urine
where is glucose reabsorbed
in the poximal tubule
how is glucose reabsorbed
secondary active transport on the luminal side by SGLT
facilitated diffusion on the base-lateral side using GLUT
what is glucosuria
glucose in urine
when does glucose appear in the urine
above renal threshold
why does glucosurea happen
the transport proteins are saturated
what is transport maximum of glucose formula
limit of substance that can be transported/unit time
what is renal threshold of glucose
the plasma concentration at which saturation occurs
what happens at transport maximum of glucose
binding sites of transport proteins get saturated
filtered load exceeds the limit of reabsorption
what is the renal threshold number
300mg/mL
what is normal blood glucose levels
100-200mg/mL
what happens in diabetes mellitus
capacity to reabsorb glucose is normal, but filtered load is beyond the threshold level to reabsorb glucose by the tubules
[glu]blood high
proteins all saturated
what happens in renal glucosuria
mutation of Na/glu cotransporter that active reabsorbs glucose in prox. tubele
how does glucose reabsorb in the prox tubules
active Na/glu cotransporter
where does most of the water reabsorption happen
proximal convoluted tubule
what does urea reabsorption depend on and why
water because water creates the concentration gradient which urea diffuses down (diffuse out of lumen)
why does tubular secretion happen
whatever the body doesnt want, it gets another chance to get rid of
what are commonly tubularly secreted substances
mostly H+ K+
choline, creatinine, penicillin
how are things tubular secreted
active transport coupled to reabsorption of Na+ (based on na k atp pump)
what is renal clearance
way of quantifying kidney function in removing substances from plasma
units for renal clearance
volume of plasma removed from kiney/ unit time
ml/min or L/h
what is the formula of clearance for substance S
S=UsV/Ps
Ps=plasma conc
Us=urinary conc
what is the L/day of clearance of inulin
180L/day
how can the clearance of inulin be used to measure GFR
Cin=GFR bc all is filtered out
GFF is inversly proportional to plasma concentration of inulin (GFR=UinV/Pin)
what is creatinine
product of muscle metabolism
how is creatinine handled in the kidneys
filtered, not reabsorbed, very slight secretion
how can creatinine estimate GFR and what is the slight error
clearance of creatinine slightly over estimates GFR
what does high creatinine mean
low GFR so the kidneys arent functioning right
clearance of substance X>GFR
X undergoes secretion
more is cleared total than just by glom
clearance of substance X
X undergoes reabsorption
more cleared by glom than is released
how is Na transported in nephron
actively
Na K atp ase
how is Cl transported in the nephrone
transported passively when Na is pumped out of the cell
how is K transported in nephron
secreted into the tubules mainly by cells of the distal and collecting ducts
where is the majority of solute excretion except for K+
proximal convoluted tubule
where is most of the water and non waste plasma solutes reabsorbed
proximal convoluted tubule
what does the loop of henle do
create osmotic gradient in medulla
reabsorb large amounts of ions
less water reabsorb
what is the role of the distal convoluted tubule
what percent reabsorption
site of fine tuning of water and solute to produce urine
12-15%
where is there little water reabsorbed but lots of ions reabsorbed
loop of henle
where is there 80% reabsorptive and secretory activities
proximal tubules
where is there 12% reabsorptive activities
distal tubule
where are most reabsorptive and secretory activities happening`
proximal tubules
