IV- Renal Physiology Flashcards
Ultrafiltrate of blood
Urine
Waste product from proteins
urea
Waste product from purines
uric acid
Waste product from muscles
creatinine
Waste product from RBCs
bilirubin
Kidney: Location
T12-L3
Kidney: Weight
150g
Kidney: Lateral to Medial
capsule, cortex, medulla, renal papilla, renal calyces (minor/major), renal pelvis
Kidney: Circulation
renal a. → segmental a. → interlobar a. → arcuate a. → interlobular a. (cortical radiate/radial a.) → afferent arteriole → glomerular capillaries → efferent arteriole → peritubular capillaries/vasa recta → interlobular v. → arcuate v. → interlobar c. → segmental v. → renal v.
Glomerular capillaries are highly _____, are responsible for _____ and are the only capillaries that lead to _____.
fenestrated, GFR, arterioles
Capillaries that supplies oxygen and glucose to tubular cells
peritubular capillaries
Erythropoietin is produced in
interstitial cells
Hairpin loop-shaped peritubular capillaries of the juxtamedullary nephrons that participate in _____ exchange.
vasa recta, countercurrent exchange
Urinary Bladder: Capacity
600mL
Urinary Bladder: Urge to urinate at
150mL - 25%
Urinary Bladder: Reflex contraction at
300mL - 50%
Urinary Bladder: Main muscle
detrusor
Urinary Bladder: Involuntary sphincter
internal sphincter
Urinary Bladder: Voluntary sphincter
external sphincter
Functional and structural unit of the kidney
nephron
There are _____ nephrons per kidney.
750K - 1M nephrons per kidney
Nephrons _____ be regenerated.
cannot
Kidneys undergo _____ upon 75% damage to kidneys.
compensatory hypertrophy
Nephrons: 75%
cortical
Nephrons: Renal cortex
cortical
Nephrons: Short - only in the cortex
cortical
Nephrons: Suppled by peritubular capillaries
cortical
Nephrons: 25%
juxtamedullary
Nephrons: Cortico-medullary junction
juxtamedullary
Nephrons: Long - goes into pyramids
juxtamedullary
Nephrons: Suppled by vasa recta
juxtamedullary
Nephron: Initial filtrating segment
renal corpuscle
Nephrons: Mainly secretes and absorbs
renal tubular system
Renal Corpuscle: The capillary endothelium is highly _____ with pores _____ in diameter.
fenestrated, 8nm or 80 angstrom in diameter
Renal Corpuscle: The capillary endothelium is ___ more permeable than skeletal capillaries.
50x
Renal Corpuscle: The capillary endothelium secretes _____ and _____.
nitric oxide, endothelin-1
Renal Corpuscle: The basement membrane has _____ spaces, is made from type __ collagen and is highly _____.
large, type IV collagen, negatively charged
Renal Corpuscle: Cells of the capillary epithelium
podocytes (visceral epithelium)
Renal Corpuscle: Parietal epithelium
Bowman’s capsule
Renal Corpuscle: Podocytes have _____ and _____ responsible for filtration.
foot processes, filtration slits
Renal Corpuscle: 3 filtration and charge barriers (innermost to outermost)
capillary endothelium, basement membrane, podocytes
Albumin is ___ in diameter but is _____. In nephrotic syndrome, the _____ barriers are destroyed leading to proteinuria.
< 8nm, negatively charged, charge barriers
Renal Corpuscle: Modified smooth muscle between capillaries
mesangial cells
Renal Corpuscle: Contractile, mediates filtration, take up immune complexes, involved in glomerular diseases
mesangial cells
Renal Corpuscle: Glomerular cells of the afferent arterioles, secrete renin
JG cells
Renal Corpuscle: Found in the walls of the DCT
macula densa
Renal Corpuscle: Monitor Na concentration in the DT (BP, GFR)
macula densa
Renal Tubular System: Workhorse
proximal convoluted tubule (PCT)
Renal Tubular System: Has Na-K-2Cl pumps
loop of Henle (LH)
Renal Tubular System: The macula densa can be found here
first part/early distal tubule (DT)
Renal Tubular System: Affected by aldosterone
second part/late distal tubule (DT)
Renal Tubular System: Affected by ADH
collecting ducts (CD)
Movement from glomerular capillaries to the Bowman’s space
Glomerular Filtration
Movement from tubules to interstitium to pertubular capillaries
Tubular Reabsorption
Movement from peritubular capillaries to interstitium to tubules
Tubular Secretion
Excretion =
(amount filtered) - (amount reabsorbed) + (amount secreted)
Glomerular Filtration: Substances that undergo filtration only, used to estimate GFR
inulin, creatinine
Glomerular Filtration: Substances that undergo filtration and partial reabsorption
electrolytes
Glomerular Filtration: Substances that undergo filtration and complete reabsorption, have a low clearance
glucose, amino acids
Glomerular Filtration: Substances that undergo filtration and secretion, have a high clearance
organic acids and bases, para-aminohippurate (PAH) - used to estimate renal blood/plasma flow
Amount filtered in the glomerular capillaries per unit time
GFR - 120mL/min or 180L/day
Fraction of renal plasma flow that is filtered
Filtration Fraction - 20%
Filtration Fraction =
GFR/RPF
Filterability of Solutes: Inversely proportional
size of solute - water, Na, glucose, inulin > myoglobin > albumin
Filterability of Solutes: ___ angstrom: filtered freely
< 20 angstrom
Filterability of Solutes: ___ angstrom: not filtered at all
> 42 angstrom
Filterability of Solutes: Charge
positive > neutral > negative
GFR =
Kf [ (Pgc-Pbs) - (Ogc-Obs) ]
Effect on GFR: Afferent Arteriole - dilate
increase
Effect on GFR: Afferent Arteriole - constrict
decrease
Effect on GFR: Efferent Arteriole - dilate
decrease
Effect on GFR: Efferent Arteriole - constrict moderately
increase
Effect on GFR: Efferent Arteriole - constrict severely
decrease
Effect on GFR: GC Hydrostatic Pressure - increased
increase
Effect on GFR: GC Oncotic Pressure - increased
decrease
Effect on GFR: BS Hydrostatic Pressure - increased
decrease
Effect on GFR: Kf - increased
increase
What causes decreased Kf in the glomerulus?
renal diseases, DM, HPN
What is the cause of increased BS Hydrostatic Pressure?
urinary tract obstruction
What are the causes of decreased GC Hydrostatic Pressure?
hypotension - decreased arterial P, ACE-I - efferent arteriole relaxation, sympathetic activity - afferent arteriole constriction
What hormones will increase GFR?
EDRF, PgE2, PgI2, bradykinin, glucocorticoids, ANP, BNP
Which hormone will preserve GFR?
angiotensin II - preferentially constrict the efferent arteriole
Angiotensin II preferentially constricts the _____ arteriole.
efferent arteriole
Renal blood flow exhibits local autoregulation at a BP between
75-160mmHg
Blood flow in the renal cortex is _____ than in the renal medulla
cortex > medulla
RBF =
(renal artery P - renal vein P) / total renal vascular resistance
Massive sympathetic stimulation that results in massive vasoconstriction of the kidneys
CNS Ischemic Response
Tubuloglomerular Feedback
Macula Densa Feedback
Tubuloglomerular Feedback: Constant ___ load is delivered to the distal tubule
sodium (Na)
Tubuloglomerular Feedback: Afferent vasoconstrictor
adenosine - systemic vasodilator, renal vasoconstrictor
Tubuloglomerular Feedback: Afferent vasodilator
nitric oxide
Primary mechanism for autoregulation of GFR
Tubuloglomerular Feedback
Glomerotubular Balance: Percentage of _____ is held constant
solute reabsorbed
Buffers effects of drastic GFR changes on urine output
Glomerotubular Balance
Intrinsic ability of tubules to increase their reabsorption rate in response to increased tubular load
Glomerotubular Balance
Tubular Processing: Substances start to appear in the urine, some nephrons exhibit saturation
Renal Threshold
Tubular Processing: All excess substances appear in the urine, all nephrons exhibit saturation
Renal Transport Maximum
Normal Plasma Glucose
80-100 mg/dL
Renal Threshold of Glucose
200 mg/dL
Renal Transport Maximum of Glucose
375 mg/dL
Does not have transport maximum and threshold, rate of transport is dependent upon electrochemical gradient, membrane permeability and time
Gradient-Time Transport
Gradient-Time Transport: Exhibited by
all passively transported solutes (Cl, Urea), some actively transported solutes (Na in the PCT)
Gradient-Time Transport: Increase in concentration
increase in rate of transport
Gradient-Time Transport: Decrease in flow rate
increase in rate of transport
Workhorse of the nephron, has low columnar cells with extensive brush border (microvilli) - unique among renal tubules
proximal convoluted tubules (PCT)
Cells of the PCT are _____ columnar, _____ metabolic, have _____ mitochondria, have _____ brush border and channels.
low columnar, highly metabolic, many mitochondria, extensive brush border and channels
PCT: Reabsorption
Isotonic Reabsorption, 100% - glucose, AAs, 66% - NaCl, H2O
PCT: Secretion
H+, organic acids/bases, drugs - rapidly filtered and almost none reabsorbed
Loop of Henle: Simple squamous with no brush border and few mitochondria, slow flow of fluid
thin segments of the loop of Henle
Loop of Henle: Simple cuboidal
thick segments of the loop of Henle
Loop of Henle: Reabsorption
20% - H2O, 25% - Na, K, Cl (Mg & Ca are also reabsorbed)
Loop of Henle: Secretion
H+ via Na-H countertransport
Loop of Henle: Impermeable to solutes, permeable to water
descending limb
Loop of Henle: Impermeable to water, permeable to solutes
ascending limb
Distal Tubule: Cells
simple cuboidal without brush border
Distal Tubule: JuxtaGlomerular Apparatus, Macula Densa, JG Cells, Lacis Cells
first part
Distal Tubule: Similar to the thick segment of LH, relatively impermeable to water
first part
Distal Tubule: Second Part
late distal tubule and cortical collecting tubule
Distal Tubule: Principal Cells, Intercalated Cells
second part
Distal Tubule: Responsive to aldosterone
second part - reabsorbs Na, secretes K & H
Distal Tubule: Secrete K, absorb Na (using Enac channels) and H2O,
Principal Cells
Distal Tubule: Secrete H (H-ATPase pump, Na-K countertransport, minimal absorption of K
Intercalated Cells
Distal Tubule: Reabsorbs ___ H2O, impermeable to ___
5% H2O, urea
Collecting Duct: Cells
cuboidal with well-defined boundaries between cells
Site for regulation of final urine volume and concntration
collecting duct
Collecting Duct: Responsive to _____, permeable to ___, secretes ___.
vasopressin, urea, H
Peritubular Capillary Hydrostatic Pressure: Increased by
increased BP
Peritubular Capillary Hydrostatic Pressure: Decreased by
afferent/efferent arteriole vasoconstriction
Peritubular Capillary Oncotic Pressure: Increased by
plasma protein concentration, filtration fraction
Effects of Increased Peritubular Capillary Hydrostatic Pressure
decreased reabsorption, increased secretion
Effects of Increased Peritubular Capillary Oncotic Pressure
increased reabsorption, decreased secretion
An increase in BP would _____ GFR and cause Pressure _____ and Pressure _____.
increase GFR, diuresis, natriuresis
Aldosterone: Site of Action
DT, early CD
Aldosterone: Effects
increase - Na & H2O reabsorption, K & H secretion
Angiotensin II: Site of Action
PCT, TAL LH, DT
Angiotensin II: Effects
increase - Na & H2O reabsorption
Catecholamines: Site of Action
PCT, TAL LH, DT, CD
Catecholamines: Effects
increase - Na & H2O reabsorption
Vasopressin: Site of Action
DT, CD
Vasopressin: Effects
increase - H2O permeability and reabsorption
ANP (atrium), BNP (ventricle): Site of Action
DT, CD
ANP (atrium), BNP (ventricle): Effects
decrease - Na reabsorption
Uroguanylin, Guanylin: Site of Action
PCT, CD
Uroguanylin, Guanylin: Effects
decrease - Na & H2O reabsorption
Dopamine: Site of Action
PCT
Dopamine: Effects
decrease - Na & H2O reabsorption
PTH: Site of Action
PCT, TAL LH, DT
PTH: Effects
decrease - phosphate reabsorption (PCT), increase - Ca reabsorption (DT), stimulates 1-alpha-hydroxylase
What are the trigger for ADH secretion?
increased plasma osmolarity, decreased BP, decreased blood volume
Effect of alcohol on ADH secretion
increased
Which hormone secreted by the DT and CD act imilar to ANP?
Urodilatin
Rate at which substances are removed from the blood in the kidneys
Renal Clearance
Renal Clearance =
( [Ux] x V ) / [Px]
If a substance has a high clearance it has
low blood level, high urine level
If a substance has a low clearance it has
high blood level, low urine level
Clearance Ranking of Substances
PAH > K > creatinine > inulin > urea > Na > glucose, AAs
Renal Clearance: Substance with the highest clearance
PAH
Renal Clearance: Substances with zero clearance
glucose, AAs
Renal Clearance: Substances whose clearance estimate GFR
inulin, BUN, creatinine
Renal Clearance: Substances whose clearance is used to estimate Renal Blood/Plasma Flow
PAH
Substances that do not appear in the urine have a clearance of ___.
zero
Substances filtered and partially reabsorbed have a clearance ___ than the GFR.
less
Substances filtered and with net secretion have a clearance ___ than the GFR.
more
Clearance of inulin is ___ the GFR.
equal to
___ of fluid per day passes through the kidneys.
180L/day
_____ plays a crucial role in water reabsorption and thus urine volume and concentration.
Vasopressin or ADH
___% of all filtered water is absorbed.
87-98.7%
Facilitates Glucose reabsorption
Na-Glucose cotransport in the proximal tubule
Transports glucose from the lumen to the PCT
SGLT-2 (secondary active transport)
Transports glucose from the PCT to the peritubular capillaries
GLUT-1 and GLUT-2 (facilitated diffusion)
___ is always coupled with the movement of H+, phosphate, AAs and lactate.
Sodium (Na)
Actively transported in all parts of the renal tubule EXCET the descending limb of the LH
Sodium (Na)
Normal Plasma K
4.2 mEq/L
___kalemia causes arrythmias while ___kalemia causes weakness.
HyperK - arrhythmia, HypoK - weakness
K+ Shift: Insulin
into cells (Na-K-ATPase pump)
K+ Shift: Aldosterone
into cells
K+ Shift: Beta-Adrenergic Stimulation
into cells
K+ Shift: Alkalosis
into cells
K+ Shift: Insulin Deficiency
out of cells
K+ Shift: Addison’s Disease
out of cells
K+ Shift: Beta-Adrenergic Blockade
out of cells
K+ Shift: Acidosis
out of cells (H-K exchange)
K+ Shift: Cell Lysis
out of cells
K+ Shift: Strenuous Exercise
out of cells
K+ Shift: Increased ECF Osmolarity
out of cells
Day-to-day regulation of K occurs in the _____ and the _____.
late DT, cortical CT
Normal Plasma Ca
2.4 mEq/L
___calcemia causes arrythmias while ___calcemia causes tetany.
HyperCa - arrhythmia, HypoCa - tetany
In acidosis, ___ Ca is bound to plasma proteins leading to ___calcemia.
less bound Ca, hyperCa
In alkalosis, ___ Ca is bound to plasma proteins leading to ___calcemia.
more bound Ca, hypoCa
Phosphate Transport Maximum
0.1 mM/min - often exceeded in diets with milk and meat
Renal phosphate reabsorption is inhibited by
PTH
Unreabsorbed _____ serve as urinary buffer for H+.
phosphate
Normal Plasma Mg
1.8 mEq/L
__% Mg stored in bones
50%
Only __% of plasma Mg is excreted daily because it is reabsorbed in the ___ and the ___.
10% excreted, PCT - 25% reabsorption, TAL LH - 65% reabsorption
__% of water is reabsorbed before reaching the CT.
> 87%
The _____ is where the final urine output and urine concentration isdetermined.
CD
Effects of High ADH
water reabsorption - high (more aquaporins), urine volume - low (min: 500 mL/day), urine concentration - high (max: 1200 mOsm/L)
Effects of Low ADH
water reabsorption - low (less aquaporins), urine volume - high (max: 20 L/day), urine concentration - low (min: 50 mOsm/L)
ADH provides the opportunity for water reabsorption while _____ provides the stimulus.
Countercurrent Mechanism
Creates the Corticopapillary Osmotic Gradient in the renal interstitium, loops of Henle
Countercurrent Multipliers
Maintains the Corticopapillary Osmotic Gradient in the renal interstitium (prevents dissipation), vasa recta
Countercurrent Exchangers
Why is the loop of Henle able to act as a countercurrent multiplier?
countercurrent flow (hairpin loop, difference in permeability to water and e- in the ascending and descending wall, Na-K-2Cl pump in the TAL LH, slow flow
What is the end-result of the countercurrent mechanism?
Corticopapillary Osmotic Gradient: 300 mOsm (PCT), 1200 mOsm (tip of LH)
Why do you need a countercurrent exchanger?
The gradient would dissipate quickly if Na and urea are removed quickly. Vasa recta preserve this gradient by moving around in circles.
Vasa recta preserve this gradient by moving around in circles.
Corticopapillary Osmotic Gradient
Urea contributes up to __% of renal medullary interstitial osmolarity resulting in hyperosmolarity of the renal medulla.
50%
ADH stimulates these urea receptors
UT-1
Effect of Urea to Urine Osmolarity
more urea reabsorbed → increase in renal interstitium concentration → more concentrated urine
The thirst center is found in the
anteroventral wall of the 3rd ventricle, preoptic nuclei
It takes ___ minutes for water to be absorbed and distributed in the body.
30-60 minutes
The micturition center is found in the
pons
Micturition is inhibited by the
cerebral cortex
pH compatible with life
6.8-8
Systems that regulate H concentrations
body fluid buffer systems (HCO3, phosphate, intracellular proteins), respiratory center (PCO2), kidneys (HCO3)
50-75% effective in returning pH back to normal within 3-12 minutes.
Respiratory Regulation of Acid-Base Balance
Respiratory Regulation of Acid-Base Balance: __% effective in returning pH back to normal within __ minutes.
50-75%, 3-12 minutes
Renal Regulation of Acid-Base Balance
secretion of excess H, reabsorption of filtered HCO3, production of new HCO3, use of ammonia (NH3) and phosphate (NaHPO4) as buffers
Due to conditions resulting in decreased ventilation
Respiratory Acidosis
Due to conditions resulting in increased ventilation
Respiratory Alkalosis
Due to conditions resulting in excess acid or loss of base
Metabolic Acidosis
Gain of acids, increased organic anions to maintain electroneutrality
HAGMA
Loss of bases, increased Cl to maintain electroneutrality, Hyperchloremic Metabolic Acidosis with Normal Anion Gap
NAGMA
Due to conditions resulting in loss of acid or gain of base
Metabolic Alkalosis
Metabolic Acidosis: Methanol
HAGMA
Metabolic Acidosis: Uremia
HAGMA
Metabolic Acidosis: DKA
HAGMA
Metabolic Acidosis: Paraldehyde
HAGMA
Metabolic Acidosis: Propylene Glycol
HAGMA
Metabolic Acidosis: Iron
HAGMA
Metabolic Acidosis: Isoniazid
HAGMA
Metabolic Acidosis: Idiopathic Acidosis
HAGMA
Metabolic Acidosis: Lactic Acid (sepsis, shock)
HAGMA
Metabolic Acidosis: Ethylene Glycol
HAGMA
Metabolic Acidosis: Ethanol
HAGMA
Metabolic Acidosis: Salicylic Acid
HAGMA
Metabolic Acidosis: Hyperalimentation
NAGMA
Metabolic Acidosis: Acetazolamide
NAGMA
Metabolic Acidosis: RTA
NAGMA
Metabolic Acidosis: Diarrhea
NAGMA
Metabolic Acidosis: Ureteroenteric Fistula
NAGMA
Metabolic Acidosis: Pancreaticoduodenal Fistula
NAGMA
