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Renal Exam 2: Part 1

What is ultrafiltrate of plasms across glomerulus? urine
What is the sum of filtration rates in all functioning nephrons and is an index of kidney function? GFR
What is the importance of GFR? evaluate severity and cause of renal disease
What does a fall in the GFR indicate? An increase? Fall-disease is progressing; Increase-suggests recovery
What is the rate at which substances are removed from plasma? Renal Clearance
What is the conservation of mass or mass balance? Fick Principle
What is the single input source to the kidney and the 2 output routes? Renal artery; Renal vein and ureter
What equation is used for renal clearance? Principle of Mass Balance C=([U]x x V)/([P]x
Renal clearance is the ratio of? urinary excretion to plasma concentration
If renal clearance increases, what happens to urinary excretion? increases
What are the units of clearance that mean the volume of plasma cleared of substance per unit time? ml/min, L/hr, L/day
What is the importance of the Concept of Clearance? can be used to measure GFR and RPF; Can determine whether a substance is reabsorbed or secreted
How do you calculate the excretion rate? Ux x V
Why do we use clearance of inulin? to measure GFR
What is the chemical composition of Inulin? polymer of fructose w/ MW of 500
Is inulin produced by the body? no administers intravenously
How is inulin filtered? freely from glomerulus into Bowman's capsule
What are 4 criteria for Inulin to measure GFR? filtered freely, Not resorbed or secreted, Neither metabolized nor produced in the kidney, Does not alter GFR in any way
Under normal conditions, what percent of the plasma that enters the glomerulus is filtered? What is this called? 15-20%; Filtration Fraction
What is the equation for the filtration fraction? FF=GFR/GPF
What percent of the plasma does not pass through a glomerulus? 10%
What is a biproduct of sceltal muslce, creatine metabolism? Creatine
What is Creatine used to estimate? GFR in clinical practice
How is creatine produced? exogenously at a constant rate and proportional to muscle mass
Is creatine secreted? to a small extent by proximal tubule cells
What is the error for creatinine? 10%
What is the clearance of Albumin? 0
Is Albumin filtered across the glomerular capillaries? no
What is the clearance of Glucose and why? zero b/c reabsorbed
Is glucose filtrated or reabsorbed? yes and yes all of it is reabsorbed
What is the clearance of Na, Urea, P, Cl higher than zero b/c it's filtered and only partially reabsorbed
What is the clearance of PAH (para-aminoHippuric acid)? Highest b/c it is filtered and secreted
What is the first step in the formation of urine? Glomerular filtration
As renal blood flow enters glomerular capillaries, a portion of that lood is filtered into? Bowman's capsule
What is the filtered fluid called and what does it contain? ultrafiltrate; water and small solutes...no protein
What are the forces responsible for glomerular filtration that are similar to forces in systemic capillaries? Starling forces
Can changes in starling forces alter GFR? yes
What phenomenon keeps GFR and RPF w/in narrow ranges? Autoregulation
What is the physical structure of glomerular cap wall and is unique to the cap wall? GFB- glomerular filtration barrier
What does the unique structure of the GFB determine? what is filtered and how much; and the composition of plasma ultrafiltrate
What are the 3 things the GFB consists of? capillary epithelium, Epithelium(filtration slits of podocytes), Basement membrane
What are the 2 things that GFB restricts the filtration of molecules? size and charge
What size of molecules does the GFB filter freely? 20-40A, anything over 40 is not filtered
What charge does GFB filter? cations and negative-charged glycoportiens on surface of GFB
What is a glomerular disease that has an increase in filtration of proteins de to infection, inflammation, immunologic damage and has a loss of glycoproteins from the GFR? Proteinuria
What occurs b/c the Starlin forces drive fluid from glomerular capillaries lumen across the filtration barrier, into Bowman's space? Ultrafiltration
What are the 4 starling forces? 2 hydrostatic and 2 oncotic (one in capillary blood and one in Bowman's space ISF)
what is Bowmaan's space analogous to and what is the oncotic pressure of this space? ISF, zero since protein filtration is negligible
What are the 2 things that determine the GFR? sum of hydrostatic and colloid osmotic forces across glomerular membrane which gives the net filtration pressure; and glomerular filtration coefficient
What are the forces favoring filtration? Pg, IIb, glomerular hydrostatic pressure (60mmhg) and Bowman's space colloid osmotic pressure (0mmhg)
What are the forces opposing filtration? Pb IIg; Bowman's space hydrostatic pressure (18mmhg) and Glomerular capillary colloid osmotic pressure (32mmhg)
What happens to GFR when Increase in Glomerular capillary filtration coefficient? increases
What happens to GFR when increase in Bowman's Capsule hydrostatic pressure? Decreases
What happens to GFR when Increase in Glomerular capilary hydrostatic pressure? Increases
What is normal Kf? 12.5ml/min/mmhg
What is a pathological condition due to increase in bowman's capsule hydrostatic pressure? Obstruction of Urinary Tract.."stones" due to deposit of Ca or uric acid
A serious reduction of GFR due to Increased bowman's capsule hydrostatic pressure can cause? damage to kidneys
What are the 3 variables determining Glomerular Capillary Hydrostatic PRessure(Pg)? Arterial pressure, afferent arteriolar resistance, efferent arteriolar resistance
What happens to Pg and GFR when arterial pressure is increased? Increase
What happens to Pg and GFR when afferent arteriolar resistance is increased? Decrease b/c less fluid...less pressure
What happens when afferent arteriols dilate? increase Pg
What happens with modest efferent arteriolar resistance? severe? modest increases GFR initially; severe decreases GFR by more than 3 fold
____ increases resistance to outflow from glomerular capillaries. constriction
What happens to FF and glomerular colloid osmotic P when constriction reduces blood flow? both increase
Constriction of afferent arterioles.... reduces GFR
Efferent arteriolar constriction if modest... raises GFR
Severe efferent constriction... decreases GFR
Urine formation results from what 3 processes? glomerular filtration; reabsorption (renal tubeles into blood); secretion (blood into renal tubules)
Filtrate rate - Reabsorption rate + secretion rate = ??? Urinary excretion rate
Urine formation begins with? filtration
Why are most substances in plasma, except for proteins, filtered freely? b/c their conc. in glomerular filtrate in Bowman's space is almost the same as in plasma
What happens when filtered fluid that leaves Bowman's space and passes thru the tubules? It is modified by reabsorption of water and specific solutes back into the blood or by rejection of other substances from peritubular capsule into tubule
Glomerular filtration produces large quantities of an ultra filtrate of plasma...how much? 180 L/day
What will be lost in urine each day if you excrete ultrafiltrate unmodified? water, Na, Cl, HCO3, and glucose
Each of these loses represents more than ____ of the amount present in entire ECF? 10 fold
Which mechanism in the epithelial cells lining the renal tubule return these substances to ciruculation and to the ECF? reabsorption mechanisms
What is the function of the secretion mechanisms in the epithelial cells? remove certain substances form the peritubular capillary blood and add it to the urine
An interstitial-type fluid is filtered across glomerular capillary into Bowman's space and the amount of a substance filtered into Bowman's space per unit time is called? Filtered Load
What is the fluid in Bowman's space and in the lumen of the nephron called? tubular fluid aka Luminar Fluid, Ultrafiltrate
Where is water reabsorbed from? solutes? water from glomerular filtrate; Solutes from peritubular capillary blood
What are some of the solutes reabsorbed? Na, Cl, HCO3, Mg, P, AAs, Citrate, Lactate, Urea
What do reabsorption mechainsms involve? transporters in the membranes of renal epithelial cells
What wll happen if reabsoprtion did not occur? most of these consituents of ECF would be lost rapidly in urine.
Substances like organic acids, organic bases, and K are secreted from? peritubular capillary blood into tubular fluid
What do secretion mechanisms involve? transports in membranes of epithelial cells
what refers to the amount of a substance excreted per unit time and is the net result of the process of filtration, reabsoprtion, and secretion? Excretion or excretion rate
What is it when filtered load is GREATER THAN excretion rate? net reabsorption
What is it when filtered load is LESS THAN excretion rate? net secretion
What is an example of Reabsorption? Glucose
At 200 mg/dL plasma glucose concentration, all of filtered glucose is reabsorbed b/c? Na-glucose cotransporters are plentiful
At 350 or above concdentrations, reabsorption is at is maximal value--> tubular transport maximum b/c? carriers are completely saturated
Plasma concentration at which glucose first appears in the urine is called ____ and it occurs at lower plasma concentration than does Tm. threshold
What is normal plasma glucose concentration? What is happening at this concentration? 70-100mg/dL; all of the filtered glucose is reabosrbed and none is excreted
What is it called when there is excretion or spilling of glucose in urine? Glucosuria
What are 3 reasons for glucosuria? Uncontrolled diabetis melitus w/ high glucose plasma concntration; During pregnancy when GFR is increased and there is an increased filtered load of glucose; Congeintal abnormalities of Na-glucose transprotes to decrease Tm
What is an example of passive reabsorption? Urea
How is urea reabsormed? in most segnments of nephron by simple diffusion
What is the rate of Urea reabsorbtion determeind by? concentration difference for urea b/w tubular fluid and blood; and permeability of epithelial cells to urea
What is an example of Secretion? PAH
What is used to measure RPF and is not produced in the body? PAH
What % of PAH is bound to plamsa proteins? 90
Is the unbound PAH filterd across glomerular capillaries? yes
What happens to the filtered load of PAH as the unbound concentration of PAH increases? increases
Where are transporters for PAH found? In peritubular membranes of proximal tubule cells
How does transpot occur w/ PAH? flood to renal tubular lumen
What happens to secretion when there is decrease in PAH concentration? increases linearly and > carriers available
What does it mean when the carriers are saturated at Tm? no further increase in secretion rate, no matter how much the PAH concentration
What happens to excretion below Tm (decreased PAH)? increase excretion w/ increase in plasma pH concentration b/c both filtration and secretion increasing
At PAH concetration above Tm, excretion increases less steeply b/c? only filtration component increases as concentration increases b/c secreation is already saturated
The kidneys recieve about what % of cardiac output and how does this rank w/ other organs? 25%; highest
Why is there such a high rate of RBF? kidneys maintain the volume and composition of the boody fluids
What 6 functions does blood flow through kidneys serve? Determines GFR indirectly, Modifies rate of solute and water reabsorption by prox tubules, Participates in conc. & dulution of urine, Delivers O2 nutrients &hormones to cells of nephron, returns Co2 & reabsorbed fluid & solutes to circulation, excretion.
How is blood flow represented? Blood flow = (mean renal arterial pressure-renal venous pressure for that orgain)/ (resistance of flow thru that organ)
RBF is ___ to pressure gradient b/w renal artery and renal vein. directly proportional
RBF is ___ of renal vasculature Inversely proportional
Renal Blood Flow = ? (Renal artery pressure - renal vein pressure) / total renal vascular resistance
What are the 2 mechanisms for autoregulation of RBF and GFR? Myogenic and Tubuloglomerular Feedback Mechanism
In myogenic mechancism, intrinsic property of vascular smooth muscle responds to changes in? arterial pressure
In mygenic mechanism, what happens when there is an increase in arterial pressure? reanal afferent arteriole is stretched and the smooth muscle contracts
Why does the RBF and GFR remain constant in myogenic mechanism? increase in resistance to arterioles offsets the increase in pressure
What does the tubuloglomerular feedback mechanism reespond to changes in? NaCl concentration of tubular flid
Tubuloglomerular feedback involves a feedback loop in which NaCl concentration of tubular fluid is sensed by what? macula densa of Jusxtaglomerular Apparatus
Once it is sensed, it is converted into a signal that affects what? afferent arteriolar resistance
Increase in GFR-->increase NaCl concentration in Henle's loop-->sensed by macula densa and converted to signal-->increase restance of afferent artiole --> decrease GFR
What are 4 effector substances that alter resistance o afferent arteriole? adenosine(con), ATP(con), metabolietes of arachadonic acid, Nitric oxide(dil)
when is Autoregulation absent? arterial pressure <90mmHg
Can RBF and GFR change slightly as arterial BP rises? yes
What is the effect of vasoconstrictors (SNS, angiotensin II, endothelin) on GFR and RBF? decrease
What is the effect of vasodilators (Prostaglandins, NO, Bradykinin) on GFR and RBF? increase except no change w/ prostaglandins
What activates sympathetic nerves to decrease RBF and GFR? fear and pain
Where is NE released? Epinephrin? NE-sympathetic nerves, Epinephrin-adrenal medulla
What is produced by the kidneys and constricts afferent and efferent arterioles to decrease both GFR and RBF? angiotenin II
What affect will PGI2 and BGE2 have in patents who hemorrahge? increase RBF, no change in GFR
What prevents severe and potentially harmful vasoconstriction and renal ischemia? a dampened vasoconstricotr effect of sympathetic nerves and angiotensin II by PGs
What is stimulated by decreased effective circulating volume, stress, angiotensin II, and sympathetic nerves? PG synthesis
what is an endothelium-derived relaxing factor that plays a vasodilatory role? NO
What increases NO production? stretch endothelial cells in arterioles
What counteracts vasoconstriction produce by angiotensin II and catacholamines? NO
Since NO also decreases total peripheral resistance, what does this do to blood pressure? Increases
When endothelin, a vasoconstricor, is elevated in glomerular diseased states, it is associated with? diabetes mellitus
What is produced by kidneys and stimulates the release of NO and PGs to increase GFR and RBF? Bradykinin
What is produced by the kidneys that is a vasoconstrictor and decreases GFR and BBF and plays a role in tubuloglomerular feedback? Adenosine
What affect does Atrial Natriuretic Peptide have on afferent and efferent arterioles? dilates afferent, constricts efferent
What is the net effect of ANP? modest increase in GFR, little change in RBF
What affect does ATP have on GFR and RBF? dual effect
How do glucocorticoids affect GFR and RBF? increase
How does histamine affect GRF and RBF? increase RBF w/out elevating GFR
what is a vasodilator prduced by the proximal tubule that increases RF and hinhibits renin secretion? Dopamine
Created by: SparkleBabies