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Renal Exam 2: Part 1
| Question | Answer |
|---|---|
| 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 |
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