Question | Answer |
What do the kidneys regulate | Inorganic Ion Balance
Osmolarity
Volume
Water |
What do the kidneys excrete | Metabolic waste(urea,uric acid, creatinine)
Foreign Chemicals (drugs) |
What do the kidneys secrete | Hormones: Renin & Epo
-1,25-dihydrocholecalcificol |
Juxtaglomerular(granular cells) secrete what? | Renin |
Interstitial cells secrete what? | Epo |
How much water is inputted per day? | 2300mL |
How much water is outputted per day? | 1200mL |
How much water is UNACCOUNTED for each day? | 1100mL (steady state) |
Pt has urinary flow of >1100ml/day. Dx? | Negative Water Balance |
Pt has urinary flow of 1100ml/day. Dx? | Steady State |
Pt has urinary flow of <1100ml/day. Dx? | Positive Water Balance |
Pt has diarrhea, what do you suspect of their sodium/water balance? | Negative Balance |
Pt on diuretic, what do you suspect of their sodium/water balance? | Negative Balance |
Pt has adrenal dysfunction(NOT enough aldosterone), what do you suspect of their sodium/water balance? | Negative Balance |
Pt on excess steroids, what do you suspect of their sodium/water balance? | Positive Balance |
Pt has congestive heart failure, what do you suspect of their sodium/water balance? | Positive Balance |
Pt has salt-retaining renal disease, what do you suspect of their sodium/water balance? | Positive Balance |
This part of the kidney is striated | Medulla |
This part of the kidney is granular | cortex |
Ureter pressure is typically high or low? | Very low |
This structure has 3 components: tubular, vascular & combined (JGA) | Nephron |
This contains the glomerulus & Bowman's Capsule | Renal Corpuscle |
This DRAINS the Bowman's Caspule where 60-80% of filtered solute & water is reabsorbed (isosmotic) | Proximal Tubule |
These descending and ascending loops generate osmotic gradients in the medulla that allow the kidney to concentrate the urine | Loop of Henle |
This is where thick ascending limb passes btwn afferent/efferent arteriole | Juxtaglomerula Appartaus (JGA) |
This has some reabsorption of water/ions. Fluid here is iso OR hyposomtic | Distal Convuluted Tubule |
This is where the final concentration of urine is adjusted | Collecting Duct |
In the collecting duct water permeability is controlled by what | Vasopressin |
These glomeruli in outer cortex have short loops of Henle that do NOT extend into the inner medulla | Cortical Nephrons |
These glomeruli near corticomedullary border have long loops of Henle and extend deep into the inner medulla. | Juxtamedullary Nephrons |
The number of juxtamedullary neprhons will control what? | The ability to produce a certain amt of concentration in the urine |
All nephrons function in what way? | In parallel (collecting ducts shared by many nephrons) |
Capillary endothelium, basement membrane & capsular epithelial cells all comprise this | Filtration barrier |
Podocytes separated by slits are present in the capsular epithelial cells. What do they constitute? | The path of filtrate flow from capillary lumen into urinary space |
This is composed of macula densa, granular cells & extraglomerula mesangial cells | JGA (Juxtaglomerula Apparatus) |
This helps control glomerula filtration rate & renin secretion (BP & volume) | JGA (Juxtaglomerula Apparatus) |
These cells found inbetween and within capillary loops of the JGA contract in response to angiotensin 2 | Mesangial cells |
This part of the peritubular capillary bed follows the loops of Henle of JGA nephrons. Found in medulla | Vasa Recta |
Cortical aa give off afferent arterioles. How many per glomerulus? | One afferent arteriole per glomerulus |
Fluid NOT filtered by kidney goes where | Efferent arterioles-->peritubular capillaries |
There are 2 arterioles (afferent & efferent) and 2 capillary beds (glomerula & peritubular) which do what | Go in series |
These specialized tubular capillaries of juxtamedullary nephrons are long, hairpin shaped that follow the loops of henle. They supply nutrients to medullary tissue & are impt for water recovery | Vasa Recta |
Renal nerves are SNS(Adrenergic: dopamine/NE) and use which receptors | Alpha1 on arterioles |
Are the kidneys PNS or SNS or both? | SNS only (Adrenergic: NE/Dopamine) |
Only adrenergic stimulation (SNS) will do what to renal blood flow & glomerula filtration rate | Will decrease renal blood flow & glomerula filtration rate |
Adrenergic stimulation (SNS) with the simultaneous release of PGE2 and PGI2 will do what to renal blood flow & glomerula filtration rate | Will reduce the reduction of renal blood flow and glomerula filtration rate
-PGE/PGI will oppose the effect of SNS |
SNS (adrenergic) stimulation of granular cells(JGA) will lead to what when beta receptors are stimulated? | Renin release |
What is the rate of glomerula filtration? | 120-125ml/min |
After glomerula filtration, what is produced? | A protein-free filtrate |
What occurs from tubular lumen to PTC | Tubular Reabsorption |
What occurs from PTC to tubuluar lumen | Tubular secretion |
Kidneys receive how much of cardiac output? | 1/4
-180L Filtrate/day
-Plasma filtered 65x/day |
Dividing the glomerula filtration rate/renal plasma flow gives you what? | Filtration Fraction |
Vasoconstriction in the renal area is mediated by which receptors | Alpha1 |
Vasoconstriction by SNS (alpha1) effects RBF & GFR how? | Decreases renal blood flow
Decreases glomerula filtration rate |
AngII, ADH, ATP & Endothelun all do what? | Vasoconstrict-->DEC RBF & GFR |
AngII constricts both afferent & efferent arterioles. Which are more sensitive to its effects? | Efferent arterioles |
ANP, Glucocorticoids, NO, Prostaglandins all do what? | Vasodilate--> INC RBF & GFR |
Constant blood flow and GFR @difft arterial pressures determined by? | Autoregulation:
Range 80-180mmHg |
This can be OVERridden by LARGE increases in sympathetic tone(vasoconstriction by SNS or other constrictors) | Autoregulation |
When would you expect to see decreased RBF & GFR? | Hypotension during severe blood loss |
Intrinsic to vascular smooth m cells it contracts in response to stretch of vessels. | Myogenic Mechanism for Autoregulation of RBF & GFR |
Increasing GFR will INC NaCl delivery to LOH which is sensed by the macula densa. This will cause resistance of the afferent arteriole(Ra) to INC-->DEC RBF&GFR | Tubuloglomerula Feedback("Flow Dependent") Autoregulation of GFR & RBF |
Signaling that affects RBF & GFR mainly by changing resistance in this arteriole | AFFerent arteriole |
This maintains constancy of salt load delivered to distal tubule | Tubuloglomerula Feedback |
What is the suspected tubuloglomerula feedback signal | Adenosine |
All small-MW solutes NOT protein-bound appear in the filtrate comparitively how w/blood plasma concentrations? | In SAME concentrations |
The fluid in Bowman's Capsule: | Protein-FREE filtrate of blood plasma |
Fenestrae-->basal lamina-->slits btwn pedicels of podocytes(bridged by diaphragms) | Route of Filtrate |
What are the MAIN barriers to proteins during filtration | Basal Lamina & Filtration Slits |
Why are proteins unable to filter into glomerula | BC slits are coated w/negative charge and cannot pass thru since proteins also negative |
What is more permeable to filtration: polycation or polyanion? | Polycation (+)charge |
Mesangial cells (produce AngII) alter filtration rate Kf how? | By decreasing |
What is the driving force for GFR? | Blood pressure in glomerula capillary (Pgc) |
What slows down GFR? | Back pressure in Bowman's Capsule (Pbc) |
What oncotic pressure is caused by proteins unable to cross the barrier, slowing GFR. Will increase as plasma is diverted into BC. | Oncotic pressure of glomerular capillary blood (pi-gc) |
Glomerula Capillary Pressure Hydrostatic Pressure | 45mmHG |
Oncotic Pressure of glomerula capillary? | 26mmHg (MEAN VALUE) |
Pressure of Bowman's Capsule? | 10mmHg |
Kf for filtration | 14ml/min/mmHg |
When afferent (Ra) and efferent (Re) BOTH INC what happens to glomerula capillary hydrostatic pressure? | There is NO EFFECT on glomerula capillary pressure if BOTH resistances INC |
When afferent (Ra) and efferent (Re) BOTH INC what happens to renal blood flow? | There is a DRAMATIC decrease in renal blood flow |
When afferent (Ra) INC and efferent (Re) stays constant what happens to glomerula capillary hydrostatic pressure? | Glomerula capillary pressure will DEC |
When afferent (Ra) INC and efferent (Re) stays constant what happens to renal blood flow? | Renal Blood Flow will DEC |
When afferent (Ra) stays constant and efferent (Re) INC what happens to glomerula capillary hydrostatic pressure? | Glomerula capillary pressure will INC |
When afferent (Ra) stays constant and efferent (Re) INC what happens to renal blood flow? | Renal blood flow will DEC |
INC glomerula surface area does what to GFR | Increase GFR |
INC renal a pressure does what to GFR | Increase GFR |
DEC afferent-arteriole resistance via afferent dilation does what to GFR | Increase GFR |
INC efferent-arteriole resistance via efferent constriction does what to GFR | Increase GFR |
INC intratubuluar pressure bc of an obstruction of tubule or extrarenal urinary system does what to GFR | Decrease GFR |
INC systemic plasma oncotic pressure does what to GFR | Decrease GFR |
DEC renal plasma flow causing an INC in osmotic pressure in glomerula capillaries will do what to GFR | Decrease GFR |
Amount of material in glomerula filtrate | Filtered Load=GFR*Px |
Amt of material lost in urine | Excretion Rate=Ux * V |
Amt of material added to (secreted) or removed (reabsorbed) from glomerula filtrate | Transport rate=Tx=FL-ER |
Positive transport rate | Reabsorption: material was removed from filtrate |
Negative transport rate | Secretion: material was added to filtrate |
Fraction of filtered mass represented by excreted mass | Fractional Excretion: FE=ER/FL |
Fractional excretion <1 | Reabsorption: material was removed from filtrate |
Fractional excretion >1 | Secretion: material was added to filtrate |
What is 100% reabsorbed | Glucose |
Transcellular & paracellular(leaky epithelium) are what | Routes of reabsorption |
What 2 barriers must you cross for transcellular reabsoption | Apical & basolateral membrane
_Diffusion thru IF & capillary wall is fast |
Perfect GFR marker is freely filtered, not reabsorbed or secreted. What is gold standard but not commonly used? | Inulin |
What is commonly used to indicate GFR | Creatinine clearance & plasma creatinine |
Produced by skeletal m @relatively constant rate from breakdown of creatinine phosphate. Freely filtered, not reabsorbed, only slightly secreted. At a steady-state conc in blood. | Creatinine |
Which levels can provide an estimate of GFR over the preceding hrs | Creatinine |
a.a. catabolism in liver makes urea which varies w/protein intake & liver function. About 1/2 of filtered urea is reabsorbed. This is NOT a good GFR marker | Blood Urea Nitrogen (BUN)
Normal: 9-18 |
What happens to reabsorption of urea when GFR is low | Reabsorption will increase |
High BUN:Cr ratio: >15 | Dehydration (DEC GFR)
Upper GI Bleeding |
Normal BUN:Cr ratio: 10-15 | Acute tubular necrosis
Loss of nephrons |
Low BUN:Cr ratio: <10 | Severe skeletal m injury(INC Cr)
Liver Dz(DEC BUN)
Malnutrition(DEC BUN) |
What is more sensitive to decreased GFR, BUN or plasma Cr | BUN |
Volume of plasma that is cleared of solute x per minute | Clearance |
Injected diuretic that inhibits osmotic water flow from lumen-->basolateral spaces. Causes Na+ back-diffusion into lumen of tubule w/INC Na+ and H20 loss. | Mannitol (in Proximal Tubule)
_INC loss of water & electrolytes in urine |
Cr clearance of 85-125 for females | Normal |
Cr clearance of 97-140 for males | Normal |
Clearance of secreted substance, lesser or greater than CCr | Clearance of secreted substance GREATER than clearance of creatine(and thus >GFR) |
Clearance of reabsorbed substance, lesser or greater than CCr | Clearance of secreted substance lESSER than clearance of creatine(and thus >GFR)
_Glucose, complete reasorption, clearance is zero |
Clearance of substance:Clearance of Inulin=1 | substance being filtered must also be a GFR marker |
Clearance of substance:Clearance of Inulin<1 | Substance Not Filtered OR
Filtered & Reabsorbed |
Clearance of substance:Clearance of Inulin >1 | Substance Filtered & secreted |
This can estimate RPF(renal plasma flow) because ALL the blood is cleared of this | Para-aminohippurate(PAH) |
Glucose uses this process to move during reabsorption | Secondary active transport w/Na+ INFLUX |
How much Na+ is reabsorbed in the proximal tubule | 67% (2/3) |
How much water is reabsorbed in the proximal tubule | 65% (2/3)
_Solute Linked |
How is Na transported across basolateral membrane | By Na/K ATPase
_H20 will follow passively |
How does Na enter proximal tubule cells | Organic cotransport & Na/H antiport |
How does Cl enter proximal tubule cells | Paracellular Routes |
How does Na leave proximal tubule cells | Na/K ATPase or via cotransport w/bicarbonate |
Stimulates Na/H exchange across apical membrane(NHE family of transporters) & INC Na reabsorption & H secretion. | Angiotensin II |
Stimulates Na reabsorption | SNS Activity |
Inhibits Na/PO4 cotransport. INC urinary excretion of PO4. | Parathyroid Hormone |
What can the loop of Henle NOT transport more than? | 200 |
Tubular Fluid/Plasma (TF/P) ratio in Bowman's space for freely filtered solutes | 1 |
What happens to osmolarity across the proximal tubule? | Osmolarity DOES NOT change |
Tubular Fluid/Plasma Conc. (TF/P) ratio=1 | Reabsorption of substance has been EXACTLY proportional to reabsorption of water |
Tubular Fluid/Plasma Conc. (TF/P) ratio <1 | Reabsorption of substance has been GREATER than reabsorption of water
_more water in plasma, than tubules
_more solute in tubules |
Tubular Fluid/Plasma Conc. (TF/P) ratio >1 | Reabsorption of substance has been LESS than reabsorption of water OR
There's net secretion of the substance
_more water in tubules, than plasma
_more solute in the filtrate |
Tubular Fluid/Plasma Inulin (TF/P) used why? | Since ONLY filtered, it's conc in the tube is solely determined by water movement |
Max rate which renal can transport a certain solute | Tubular Maximum (Tm)
_caused by saturation of membrane transport proteins |
Fluid leaving LOH more or less dilute than other fluids? | MORE dilute. |
Below Tm | All filtered load is reabsorbed into tubules |
Above Tm | Extra filtered load is excreted |
Where are Tm's usually found? | Proximal Tubule |
Where glucose first appears in the urine. Depends on the GFR | Threshold of plasma |
What happens to the threshold when you decrease GFR? | Decreasing filtration rate will increase the threshold(not all receptors are full therefore takes longer to saturate) |
What happens to the threshold when you increase GFR? | Increasing filtration rate will decrease the threshold(easier to saturate all the receptors) |
Causes back-diffusion into lumen of tubule w/INC Na+ and water loss (diuresis). INC water loss & electrolytes in urine. | Mannitol
_Osmotic Diuresis |
Where is the Na/K pump always present? | Basolateral membrane twds ISF of tubule |
Furosemide(lasix) a loop diuretic blocks this | Na/K/2Cl- transporter (in Thick Ascending Limb) |
What stimulates the Na/K/2Cl transporter | ADH
_Stimulation can be blocked by Loop diuretic(lasix) |
Can result in a rapid loss of Na & H20 (polyuria) | Osmotic Diuresis |
Occurs w/high filtered urea load | Osmotic Diuresis
_rapid loss of Na/H20(polyuria) |
Occurs when gluose load exceeds Tm in DM patients | Osmotic Diuresis
_rapid loss of Na/H20(polyuria) |
Non-reabsorbed carbohydrate that's given IV to induce osmotic diuresis | Mannitol
_rapid loss of Na/H20(polyuria) |
Is tubuluar secretion specific or non-specific? | VERY non-specific |
Typical cmpds SECRETED | Metabolites, waste products, foreign chemicals tagged by liver |
Liver will tag things w/glucoronic acid or sulfate. What does this do? | Promotes secretion into filtrate |
How are organic anions (PAH) secreted? | Via tertiary active transport |
PAH is taken into filtrate(secreted) in exchange for what? | alpha-KG will go back to blood |
How does PAH leave on the apical side twds the filtrate for secretion? | PAH-anion transporter |
The apical side faces which substance: plasma or filtrate | Filtrate |
If you have INC plasma levels of an ion, how will it effect other anions? | Secretion of anions will be inhibited since compete for same transporter. |
Infusion of PAH with penicillin is used why? | Extends penicillin's half-life by inhibiting it's secretion into filtrate |
Stimulates Na+ reabsorption in late distal tubule & collecting duct(principal cells) | Aldosterone |
Stimulates K+ secretion so that Na+ can be reabsorbed | Aldosterone |
Angiotensin II stimulates the release of this | Aldosterone |
K+ plasma stimulates the release of this | Aldosterone |
Vasoconstrictor which stimulates aldosterone release & Na/H exchange in the proximal tubule | Angiotensin II |
Functions favor salt retention & elevation of arterial BP | Angiotensin II |
Levels of this hormone which favors salt retention & elevation of arterial BP is controlled by renin | Angiotensin II |
Renin release by JGA has 3 components | 1)Intrarenal baroreceptors
2)Macula Densa
3)Renal SNS |
Granular cells of JGA respond to pressure(stretch) in AFFerent arterioles. Release of renin INVERSELY related to pressure in AFFerent arterioles | Intrarenal baroreceptors |
Pressure in afferent arterioles rises, what happens to renin release? | Renin release decreases which decreases blood volume to decrease blood pressure |
Pressure in afferent arterioles drops, what happens to renin release? | Renin release increases which increases blood volume to increase blood pressure |
Senses flow to distal tubule(GFR) and renin release is INVERSELY related to GFR | Macula Densa |
GFR increases, what happens to renin release | Renin release decreases which decreases blood volume to decrease blood pressure |
GFR decreases, what happens to renin release | Renin release increases which increases blood volume to increase blood pressure |
Stimulation of these increases renin release via b-receptor stimulation | Renal Sympathetic nn |
A hemorrhage would do what to renin? | Increase renin secretion which increases blood volume to increase blood pressure |
A hemorrhage would do what to angiotensin 2? | Increase angiotensin 2 which increases blood volume to increase blood pressure |
A hemorrhage would do what to aldosterone? | Increase aldosterone which increases blood volume to increase blood pressure |
What is the effect of lowering blood volume? | Lowers blood pressure |
Released from atria when pressures are high, increases NaCl excretion by INC GFR. | Atrial Natriuretic Peptide(ANP) |
Dilates the afferent arteriole & INC GFR & the filtered load of NaCl | Atrial Natriuretic Peptide(ANP) |
Decreases NaCl reabsorption by the collecting duct by directly inhibiting renin/aldosterone secretion AND Na+ uptake by the medullary collecting duct | Atrial Natriuretic Peptide(ANP) |
MOST important hormone regulating water balance that's released from pituitary when plasma osmolality INC | ADH(Antidiuretic Hormone) |
MOST important hormone regulating water balance that's released from pituitary when plasma volume DEC | ADH(Antidiuretic Hormone) |
Causes the movement of aquaporins to control water balance | ADH(Antidiuretic Hormone) |
Though an impt hormone to regulate water, has little effect on NaCl excretion | ADH(Antidiuretic Hormone) |
Hypovolemia senses SMALL changes in plasma osmolarity via OSMORECEPTORS. Stimulate this: | ADH(Antidiuretic Hormone) |
Hypovolemia senses LARGE changes in plasma osmolarity via ARTERIAL & L ATRIAL BARORECEPTORS. Stimulate this: | ADH(Antidiuretic Hormone) |
INC Na/K/2Cl cotransporters in the LOH increasing the medullary gradient | ADH(Antidiuretic Hormone) |
INC permeability of the collecting duct to water | ADH(Antidiuretic Hormone) |
INC permeability of inner medullary collecting duct to urea | ADH(Antidiuretic Hormone) |
Avg Osmolarity level | 290mOsm/L |
During a hemorrhage what happens to ADH secretion? | ADH secretion increases in order to raise plasma volumes & thus raise blood pressure. Will lower water excretion & increase its reabsorption |
During a hemorrhage what happens to too much water that's ingested? | ADH secretion decreases, and water reabsorption decreases and excess water is excreted |
ml/min of plasma cleared of a given substance | Clearance |
ml/min of plasma cleared of osmotically active particles | Osmolar Clearance= (Uosm*V)/Posm |
Positive osmolar balance is a sign of gaining osmoles & water in plasma. Progressing to edema. What's ur Osmolar clearance? | DEC Osmolar Clearance(water gain) |
Decreased GFR causes edema by causing this | DEC Osmolar Clearance(water gain) |
Increased aldosterone causes edema by causing this | DEC Osmolar Clearance(water gain) |
"Dumping" osmolytes leads to a loss of ECF. How does this effect osmolar clearance? | INC Osmolar Clearance(water loss) |
Diuretic reduce the ability of the kidney to reabsorb normally. How does this effect osmolar clearance? | INC Osmolar Clearance(water loss) |
Reduced aldosterone reduce the ability of the kidney to reabsorb normally. How does this effect osmolar clearance? | INC Osmolar Clearance(water loss) |
What would it mean if the osmotic clearance=urine flow | Urine is isotonic |
Volume is greater than osmotic clearance | Additional solute-free water is being LOST from the body (urine is HYPOtonic) |
Volume is less than osmotic clearance | Additional solute-free water is being RETURNED to the body (urine is HYPERtonic) |
If you take the urine flow-osmotic clearance, the difference gives you what? | Amt of solute-free water lost/saved |
ml/min of solute-free water excreted by the kidneys | Water clearance=Volume-Osmotic Clearance |
Water Clearance is negative | Solute-free water being conserved by the body |
Water Clearance is positive | Solute-free water being excreted by the body
_Dilute urine |