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What are the 3 general kidney functions?
1. Regulation of Body's internal environmnt - H2O conc., inorganic ion compstn, ECF
2. Removal of metabolic waste, drugs, foreign chemicals.
3. Activation of hormones.
What 4 ways does the kidney regulate internal environment?
1. By diluting/conc. urine
2. By regulating Na output
3. By regulating K+ output
4. By regulating acid/base balance
What 3 major wasteproducts do the kidneys remove from plasma?
1. Urea
2. Uric acid
3. Creatinine
What 3 hormones are released from the kidneys?
1. Renin
2. Erythropoietin
3. Vitamin D
IN general, what structures does urine flow when being formed/eliminated?
Kidneys -> ureters -> bladder ->
urethra -> outside.
what are the functional subunits of the kidney? how many are there per kidney?
Nephrons --> app. 1 million per kidney.
What are the 2 main components of a nephron?
1. Renal corpuscle
2. Tubule
What is a glomerulus?
a tuft of interconnected capillary loops, supplied by the afferent arteriole and relieved by the efferent arteriole.
what do the glomeruli reside in?
Bowman's capsule
how much blood plasma is filtered from the glomeruli into bowman's capsule?
What is filtration?
What's another thing filtrate is sometimes called?
the removal of plasma (w/ no cells or proteins) from the blood of the glomeruli into the tubule.
What are the two types of nephrons in a kidney?

What is the ratio of the two?
1. Superficial, cortical = 85%
2. Juxtamedullary - 15%
What is the order of fluid flow through the various components of a nephron tubule?
1. Bowman's capsule/capill tuft
2. Proximal tubule
3. Loope of henle (asc/desc)
4. Distal tubule
5. Collecting duct
-Out the renal pelvis, etc.
What characterizes juxtamedullary nephrons?
What is their purpose?
They reach into the inner medulla, not just the cortex.
Purpose: to concentrate urine.
How far into the kidney do cortical nephrons reach?
to the outer medulla (despite their being called CORTICAL)
Where are macula densa cells?
What is their function?
In the ascending limb wall.
Function: to detect increased Na+ in filtrate.
what are juxtaglomerular cells?
secretory cells in the wall of the afferent arteriole that secrete renin.
where exactly are the macula densa and juxtaglom. cells?
as the asc. limb becomes the distal convuluted tubule; it passes right close to the afferent arteriole bringing these cells into close proxim.
what is the juxtaglomerular apparatus?
the combination of macula densa cells and juxtaglomerular cells.
what does dr. lobner call juxtaglomerular cells?
granular cells.
How do macula densa cells respond to increased sodium in the filtrate?
Release something(?) that constricts the Afferent Arteriole.
What is the result of constricting the Aff. arteriole?
Decrease in filtration, Na+ filtratn, Na+ in filtrate --> decreased Sodium loss!!!
How do the granular cells operate?
1. Detect decreased BP; stimulates Renin release.
2. Activates Angiotensinogen -> angiotensin 1
3. Activates Angiotensin II in lungs.
4. Activates general vasoconstriction.
5. Increases BP
What is the purpose of granular (juxtamedullary) cells in a nutshell?
to increase bp when it is decreased.
How many arterioles/capillary beds are in each nephron?
2 of each - 2 arterioles in series, with 2 capillary beds in between.
What are:
Filt: glomerulus -> nephron
Reab: Nephron -> blood
Secr: Blood -> nephron
Excr: removing filtrate waste.
What is the equation for total excretion?
Excretion = (filt + secr) - Reab
What 2 factors determine what/howmuch is filtered by the glomerulus?
1. Permeability
2. Starling forces
What are the 3 barriers to glomerular filtration?
1. RBCs
2. Podocytes (nonbarrier?)
3. Basement membrane - the main barrier
How does the basement membrane of bowman's capsule prevent filtration?
it is negatively charged, and therefore prevents large negatively charged (plasma proteins) from passing through.
what 7 things are filtered by bowman's capsule?
20% of:
amino acids
Na Cl K Ca H2O
what 3 forces determine glomerular filtration?
-Glomerular Capillary Hydrostatic pressure
-Bowman's space Hydrostatic pressure
-Osmotic force of plasma protein
Glomerular and bowman's space hydrostatic pressure
and osmotic pressure (Pi)
how does bowman's space oppose filtration?
it has higher water concentration than the glomerulus because plasma proteins don't filter into bowman's capsule.
the osmotic pressure of glomerular capillaries is 29; in normal capill its 24; why?
so much plasma flows out, the remaining blood is concentrated.
What is the net glomerular filtration pressure?
GFP = Pgc - Pbs - Pi-gc
What regulates filtration/absptn in a normal systemic capillary?
Capillary hydrostatic minus oncotic pressure - which one is larger determines direction of fluid flow.
How can filtration occur if ther's always bs hydrostatic pressure and glomerular oncotic pressure opposing it?
the glomerular hydrostatic pressure is always greater than the sum of the other two, so net filtration pressure is positive.
how does increasing renal blood flow change GFR?
it increases GFR, thence urinary output too.
B/c they are directly ppnl.
what is the GFR equation?
GFR = Kf x net filtr pressure
how much plasma is filtered per minute and per cay?

how often is the body's plasma filtered?
125 ml/min
180 L/day

the 3 liters of body plasma is filtered 60 x per day
what does autoregulation refer to?
the fact that the renal blood flow is relatively constant despite changes in MAP. If cardiac output increases, blood flows ELSEWHERE.
what would happen if autoregulation didn't occur?
If MAP increased, so would cardiac output and RBF; thus urine output too and you'd pee everytime you exercised.
What happens if MAP decreases?
autoregulation maintains GFR, which is good b/c blood will continue to be filtered.
How, mechanically, does autoregulation change blood flow?
by changing RESISTANCE of renal arterioles.
what are 2 hypotheses regarding increased resistance for autoregulation?
1. Myogenic hypothesis
2. Tubuloglomerular feedback hypothesis
what does the myogenic hypothesis propose?
when MAP increases, it stretches renal arteries; this causes vasoconstriction which increases resistance.
what does the tubuloglomerular feedback hypothesis propose?
that the juxtaglomerular apparatus is involved.
How does the juxtaglomerular apparatus alter RBF in response to increased MAP for autoreg?
1. Incr MAP causes two things: a)increased glomerular blood flow, b)incr. glom hydrostat pressure
2. both increase GFR, thus Na filtration.
3. Mac densa detects Na+ incr. and release SOMETHING
4. Afferent arterioles constrict.
5. Pgc decreases, thus RBF decreases.
Other than autoregulation, what factors influence RBF?
Sympathetic nervous system constricts the afferent art'ole -> decr. RBF and GFR and urine formation.
(which is good, don't want to pee while fighting/flighting)

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