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146 Cards in this Set

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What are the 4 ways in which the kidneys maintain constancy of interstitial fluid?
-regulation of salt and water balance
-excretion of waste products of metabolism
-excretion of toxic substances
-regulation of acid-base balance
Which segments of the nephron are normally found in the renal cortex?
-glomeruli
-convoluted tubules
-thick tubules
Which segments of the nephron are normally found in the renal medulla?
-thin loops of Henle
-collecting ducts
What is a medullary ray?
a segment of medulla which extends into the cortex
What is the order of vessels through which blood flows, starting with the renal artery?
-renal artery
-interlobar artery
-arcuate artery
-interlobular artery
-intralobular artery
-afferent arterioles
-glomerular capillaries
-efferent arteriole
-peritubular capillaries
-vasa recta
Where in the lobule is the arcuate artery found?
the junction of the cortex and medulla
Where in the lobule is the vasa recta found?
medulla, next to the loop of Henle
What is the difference between the descending and ascending parts of the vasa recta?
-descending has continuous epithelium
-ascending has fenestrated endothelium
What type of epithelial cells line Bowman's capsule?
-podocytes
-simple squamous
What type of epithelial cells line the proximal convoluted tubule? What type of tight junctions are present?
-cuboidal
-very leaky tight junctions
What are the 3 layers of the basal lamina?
-lamina rara interna
-lamina densa
-lamina rara externa
How are proteins prevented from passing to the urinary space from the glomerular capillaries?
-basal lamina contains heparan sulfate, which acts as a size and charge filter
-proteins in the blood contribute to the filtering of others
What are possible causes of leaking blood into the urine?
-protein leakage across basal lamina (e.g. low Ig levels)
-autoimmune diseases
-diabetes
contribute to breaking of basal lamina
What types of cells are found in the juxtaglomerular apparatus?
-JG cells (specialized smooth muscle cells of afferent arteriole)
-macula densa cells
-Lacis cells (extraglomerular mesangial cells)
-efferent arteriole cells
What is the purpose of JG cells?
-secrete erythrogenin and renin
-receive information from macula densa cells
What is the purpose of macula densa cells?
sense sodium in distal convoluted tubule and communicate finding to JG cells
What is the purpose of Lacis cells?
reservoir of mesangial cells used in the glomerulus
What is the purpose of mesangial cells?
-unclogs and reconditions the filter
-long cell processes phagocytose protein deposits
Why is there no basement membrane between JG cells and endothelial cells?
the arteriole can stretch more easily and blood pressure can be measured by baroreceptors
What factors contribute to communication between macula densa cells and JG cells?
-no basement membrane between them
-Golgi of macula densa cells faces JG cells
What is the mechanism of action of renin?
cleaves plasma angiotensinogen to angiotensin I
Where in the body is angiotensin I converted to angiotensin II?
lungs
How does angiotensin II increase arterial pressure in the short term?
induces contraction of smooth muscle in walls of arterioles
How does angiotensin II increase arterial pressure in the long term?
-induces zona glomerulosa of adrenal cortex to release aldosterone
-distal tubules take up more sodium from filtrate to blood
-water follows to increase blood volume
In which portion of the nephron are microvilli found?
proximal convoluted tubule / thick descending
In which portion of the nephron can a large number of lysosomes be found?
proximal convoluted tubule / thick descending
What is the function of the proximal convoluted tubule / thick descending?
reabsorbs:
-glucose
-amino acids/proteins
-Na+, Ca2+, other ions
Why do the cells of the proximal convoluted tubule appear pink microscopically?
lysosomes and mitochondria stain pink
What is responsible for the central "mush" seen in proximal convoluted tubule cells under the microscope?
enzymes digest microvilli after death
What is the longest part of a nephron?
proximal convoluted / thick descending tubule
What type of epithelial cells line the loop of Henle?
simple squamous
What type of epithelial cells line the distal convoluted / thick ascending tubule? What type of junctions are present?
-cuboidal
-extensive tight junctions
Which type of cell in the nephron has the most basolateral interdigitations with mitochondria?
distal convoluted / thick ascending tubule
What is the purpose of the distal convoluted / thick ascending tubule?
-reabsorption of remaining sodium
-exchange of Na+ for K+, NH4+, or H+ (ion and acid-base balance)
On which part of the nephron does aldosterone work?
distal convoluted / thick ascending tubule
What is the purpose of a cell having basolateral interdigitations of plasma membrane with mitochondria?
ATP production for the movement of ions
On which part of the nephron does ADH work? What is its mechanism of action?
-collecting ducts
-causes cytoplasmic vesicles containing aquaporins to fuse with plasma membrane, making cells permeable to water
-activating UT1, a urea carrier protein
What is the purpose of the collecting ducts?
-transfer urine to urethra through calyces
-variable water reabsorption
-minority of cells actively move ions
What type of epithelial cells line the collecting ducts? What type of junctions are present?
-cuboidal (smaller ducts), columnar, and transitional (largest ducts)
-extremely tight tight junctions
What are ducts of Bellini?
largest collecting ducts; transfer urine to the calyces
What type of epithelial cells line the calyx and ureter? Why?
-transitional stretched epithelium
-more impermeable and protective
What is the area cribosa?
surface of the papilla (apex of each renal pyramid)
What is the orientation of the innermost smooth muscle layer around the ureter? Why?
longitudinal, because fluid is being moved by peristalsis
Why is transitional epithelium pink under the microscope?
reinforced plasma membrane into which intermediate filaments are inserted to prevent over-stretching
What role does glycocalyx have in the urinary tract?
-prevent cell damage by caustic urine
-prevent water movement into or out of cells
-anti-stick agent for bacteria
What type of epithelial cells are found in the urethra?
-transitional (near bladder)
-pseudostratified/mucosal (middle)
-stratified squamous (near end)
What are the properties of water which are related to temperature/heat?
-high heat capacity
-high heat of vaporization
-good heat conductivity
-large freezing to boiling point range
What are the properties of water which are related to its effectiveness as a solvent?
-dissolves largest number of compounds compared to other liquids
-high dielectric constant (gets electrolytes apart)
-self-ionizes (rapid diffusion of OH- and H+)
Which type of tissue contains the most water in the body? Which type contains the least?
-muscle contains the most water
-adipose tissue contains the least
What percentage of lean body weight is water (TBW)? What percentage of normal body weight is water?
-73% of lean body weight is water
-60% of normal body weight is water
Why do males have a higher percentage of total body water than females?
males have:
-more muscle
-less adipose tissue
Why do younger people have a higher percentage of total body water than older people?
younger people have:
-more easily hydrated connective tissue
-more muscle
-less adipose tissue
What is a normal water turnover rate for adults? For infants?
-adults: 2.5% body wt./day
-infants: 10-15% body wt./day
What percentage of normal body weight is intracellular fluid?
40%
What percentage of normal body weight is extracellular fluid?
20%
What are the different types of extracellular fluid found in the body?
-interstitial (12% normal body weight)
-bone (3%)
-plasma (4.5%)
-connective tissue (4.5%)
How can total body water be measured using markers?
D2O and antipyrine are permeant to all cells. Add known amount and measure concentration → calculate volume.
How can extracellular fluid be measured using markers?
Inulin and mannitol are impermeant to all cells. Add known amount and measure concentration → calculate volume.
How can plasma volume be measured using markers?
Evans Blue and 121I-albumin are impermeant to vascular walls. Add known amount and measure concentration → calculate volume.
What is the percentage of protein in plasma? In plasma water?
-plasma contains 5-7% protein
-plasma water does not contain protein
What is the percentage of protein in interstitial fluid?
1%
Do ions appear more concentrated in plasma or plasma water? Why?
-plasma water
-the proteins in plasma amplify the total volume, lowering the apparent [ion]
What is the Osmotic Equilibrium Rule for compartment volumes?
cells are water permeable; water moves fast:
-plasma osmolality = ISF osmolality
-extracellular fluid osmolality = intracellular fluid osmolality
-2 x [Na+] = plasma osmolality (hyponatremia = hypoosmotic, hypernatremia = hyperosmotic)
What are the exceptions to the 2 x [Na+] = plasma osmolality rule?
molecules which are permeant, increase plasma osmolality, and don't affect cell volume:
-hyperglycemia
-uremia
What are the six rules for compartment volumes?
-osmotic equilibrium
-compartment volume depends on number of particles inside
-Na+ is only in ECF, amount varies
-K+ is only in ICF, amount is constant
-total ICF solute content remains constant
-disturbances start in ECF
What is hypotonic dehydration?
↓ECF volume
↓ECF osmolality
What is isotonic dehydration?
↓ECF volume
ECF osmolality normal
What is hypertonic dehydration?
↓ECF volume
↑ECF osmolality
What is hypotonic overhydration?
↑ECF volume
↓ECF osmolality
What is isotonic overhydration?
↑ECF volume
ECF osmolality normal
What is hypertonic overhydration?
↑ECF volume
↑ECF osmolality
What are the major functions of the kidney?
-maintain volume and blood pressure
-control of body fluid composition
-hormone production
-gluconeogenesis
What factors affect which molecules can be filtered through the glomerulus?
-molecular weight (filtered: < 5,000; partially filtered: 5,000 - 70,000)
-shape (round > straight)
-charge (positive > negative)
How do the hydrostatic pressure and oncotic pressure change along the length of the glomerular capillary?
-hydrostatic pressure stays the same
-oncotic pressure increases
How is glomerular filtration rate calculated?
GFR = Kf x [Pg - (Pbs + πg)]
How can glomerular capillary pressure be increased without changing the renal artery pressure or the peritubular capillary pressure
-decrease afferent arteriole resistance
-increase efferent arteriole resistance
How can glomerular capillary pressure be decreased without changing the renal artery pressure or the peritubular capillary pressure?
-increase afferent arteriole resistance
-decrease efferent arteriole resistance
What is the effect of increasing the afferent arteriolar resistance on blood flow and glomerular filtration rate?
- ↓blood flow
- ↓glomerular filtration rate
What is the effect of increasing the efferent arteriolar resistance on blood flow and glomerular filtration rate?
- ↓blood flow
- ↑glomerular filtration rate
What mechanisms control afferent arteriolar resistance?
-direct sympathetic innervation (α1-adrenergic)
-stretch response (increase in blood pressure causes contraction)
-tubuloglomerular feedback from macula densa (increase in NaCl delivery causes contraction)
-angiotensin II (increase causes weak contraction)
What mechanisms control efferent arteriolar resistance?
contract in response to angiotensin II that is produced in response to hypovolemic stimuli
What is the main mechanism for maintaining GFR during hypotension/hypovolemia?
angiotensin II
What is the main mechanism for limiting GFR during hypertension/hypervolemia?
tubuloglomerular filtration
What are the requirements a marker must meet in order to be used in calculating GFR?
-stable circulating concentration
-freely filtered
-not acted on by rest of nephron
-non-toxic
How is GFR calculated using concentrations of a chosen marker?
GFR = rate of urine formation x [marker] in urine / [marker] in plasma
What is the definition of clearance?
volume of plasma containing the amount of a substance cleared from the plasma per unit time
How can clearance of a marker indicate its absorption?
if inulin clearance > marker clearance, that marker was absorbed
How can clearance of a marker indicate its secretion?
if inulin clearance < marker clearance, that marker was secreted
Why is creatinine ideal for measuring GFR?
-it is a metabolic by-product
-freely filtered
-secreted only slightly
What is a normal rate of creatinine production for males? For females?
-males: 20-25 mg/kg/day
-females: 15-20 mg/kg/day
What is a normal plasma creatinine level for males? For females?
-males: 1.25 mg%
-females: 1.1 mg%
Why is urea not a good marker for measuring GFR?
dehydration state, protein intake, and exercise increase plasma urea concentrations independent of GFR
Why is PAH a good marker for measuring renal plasma flow?
excretion of PAH matches rate of renal delivery of PAH
How is renal plasma flow related to renal blood flow?
renal plasma flow = renal blood flow (1 - Hct.)
What is the filtration fraction? How is it calculated?
-fraction of the plasma delivered to the glomerulus that passes through the filter
-FF = GFR/RPF
What percentage of the volume of plasma delivered to the glomerulus is typically filtered in one pass?
20%
What is the major purpose of the proximal convoluted tubule?
reabsorption of the filtered fluid
What is the role of Na/K ATPase in the proximal convoluted tubule?
create a driving force for Na+ absorption
What is the role of Na+/H+ antitransporter in the proximal convoluted tubule?
-acidifies the luminal fluid
-neutralizes and removes HCO3-
-sets up Cl- ion gradient
What is glomerular tubular balance?
mechanism that keeps the fraction of glomerular filtrate reabsorbed from the proximal convoluted tubule constant (66%)
What are the exceptions to glomerular tubular balance?
-90% of filtered HCO3- is reabsorbed in PCT
-100% of glucose is reabsorbed in PCT
Why does diabetes mellitus cause excessive urine production?
the excess glucose in the filtrate osmotically traps water, leading to large volumes of fluid being passed on to the distal nephron
What is the pars recta? What does it do?
-straight part of the proximal convoluted tubule
-responsible for organic solute secretion
What is the purpose of the loop of Henle?
concentrate urine above iso-osmotic
What is the role of NKCC2 in the distal nephron?
transport 1 Na+, 1 K+, and 2 Cl- ions across the apical membrane in the thick ascending limb
What type of solutes pass through the tight junctions in the thick ascending limb?
Na+, Mg2+, Ca2+ from tubule lumen to interstitium
What transporters are present in the basolateral membrane of cells in the proximal convoluted tubule?
-Na+/K+ ATPase
-GLUT (glucose transporter)
What transporters are present in the apical membrane of cells in the proximal convoluted tubule?
-Na+/glucose cotransporter
-Na+/amino acid cotransporter
-Na+/H+ antiporter
What solutes pass through the tight junctions in the proximal convoluted tubule?
Cl- and H2O, from the tubule to the interstitium
What transporters are found in the basolateral membrane of cells in the thick ascending limb?
-K+ (to plasma)
-Cl- (to plasma)
-Na+/K+ ATPase
What transporters are found in the apical membrane of cells in the thick ascending limb?
-NKCC2 cotransporter
-K+ recycler
-Na+/H+ cotransporter (Na+ absorption, H+ secretion)
What transporters are found in the basolateral membrane of cells in the distal convoluted tubule?
-Na+/K+ ATPase
-K+ channel (to plasma)
-Cl- channel (to plasma)
-Ca2+/3 Na+ antitransporter (Ca2+ absorption)
What transporters are found in the apical membrane of cells in the distal convoluted tubule?
-Na+/Cl- cotransporter
-Ca2+ channel (absorption)
What transporters are found in the basolateral membrane of principal cells in the collecting duct?
-K+ channel (to plasma)
-aquaporin
-Na+/K+ ATPase
What transporters are found in the apical membrane of principal cells in the collecting duct?
-Na+ channel (absorption)
-K+ channel (secretion)
What is the effect of aldosterone on the collecting duct?
stimulate:
-Na+ absorption
-K+ secretion
in the principal cells
What transporters are found in the basolateral membrane of Type A intercalated cells in the collecting duct?
-K+ channel (to plasma)
-HCO3-/Cl- antiporter (HCO3- absorption)
What transporters are found in the apical membrane of Type A intercalated cells in the collecting duct?
-K+/H+ antiporter (K+ absorption)
-H+ channel (secretion)
How does hypokalemia alter the K+ regulation by the collecting duct?
increased K+ absorption by Type A intercalated cells
How does hyperkalemia alter the K+ regulation by the collecting duct?
increased K+ secretion by principal cells
How does acidosis alter the acid-base regulation by the collecting duct?
increase in H+ secretion and HCO3- absorption by Type A intercalated cells
What transporters are found in the basolateral membrane of Type B intercalated cells in the collecting duct?
H+ ATPase (to plasma)
What transporters are found in the apical membrane of Type B intercalated cells in the collecting duct?
Cl-/HCO3- antiporter (HCO3- secretion)
How does alkalosis alter the acid-base regulation by the collecting duct?
increase in HCO3- secretion and H+ absorption by Type B intercalated cells
What are the two types of sensors that affect body fluid osmolality?
-osmoreceptors in hypothalamus
-stretch receptors in carotid/aorta, and pulmonary veins/left atrium
What is the effect of increased osmolality on the osmoreceptors in the hypothalamus?
-ADH release from posterior pituitary
-stimulation of the cerebral cortex to induce thirst (by angiotensin II)
What is the effect of increased volume on the stretch receptors in the arterial and venous systems?
inhibition of ADH release and thirst
What are the effects of alcohol, nicotine, nausea, and stress on ADH release?
-alcohol: supression
-nicotine: stimulation
-nausea: stimulation
-stress: stimulation
What is free H2O clearance?
the theoretical volume of distilled H2O that must be extracted from hypotonic urine to make it isotonic with plasma
What is negative free H2O?
volume of distilled water that must be added to make hypertonic urine isotonic with plasma
What is the treatment for plasma hyperosmolality?
restore fluids carefully (Δ < 30 mOsm / 4-6 hours)
What is the treatment for plasma hypoosmolality?
withhold fluids
Which will stimulate the most Na+ excretion:
-whole blood transfusion
-hyperoncotic albumin
or
-isotonic saline?
isotonic saline (will cause largest increase in ISF volume)
What is pressure diuresis?
increase in blood pressure causes:
-hormone suppression
-washing out of medullary gradient
-decrease activity of Na+/H+ in proximal convoluted tubule
-increase peritubular capillary pressure opposing Na+ uptake from ISF
How do catecholamines affect Na+ absorption under conditions of low ECV?
adrenal medulla releases norepinephrine and epinephrine to stimulate Na+ absorption
How do catecholamines affect Na+ absorption under conditions of high ECV?
renal dopaminergic nerves release dopamine to inhibit Na+ absorption
What is atrial natriuretic peptide?
-released from walls of the atrium in response to high blood pressure
-dilates afferent arteriole to increase renal blood flow
What is 3rd spacing?
accumulation of fluids in spaces which are not well perfused
What is nephrotic syndrome?
loss of protein in urine
What is natriuretic hormone?
affects the connecting system and final modulation of sodium in the urine (stimulates Na+ absorption)
How are ANP levels different in congestive heart failure compared with dehydration?
-congestive heart failure: ANP is high because atrial pressure is high
-dehydration: ANP is low because atrial pressure is low
What type of diuretic acts on the proximal convoluted tubule? What are the side effects?
-carbonic anhydrase inhibitor
-buildup of H2CO3, H+, and HCO3- → acidosis
-increase in Na+, HCO3-, K+, PO43- in the urine
What type of diuretic acts on the thick ascending limb of Henle's loop? What are the side effects?
-blocks NKCC2
-drops concentrating ability of the medulla
-hypokalemic metabolic alkalosis
What type of diuretic acts on the distal convoluted tubule? What are the side effects?
-thiazides (block NaCl cotransporter)
-enhances K+ and H+ loss in distal nephron (as compensation)
-hypokalemic metabolic acidosis
What type of diuretic acts on the collecting ducts? What are the side effects?
-block aldosterone or Na+ channel
-block Na+ absorption and K+, H+ secretion
-hyperkalemic metabolic acidosis
What are typical serum levels for:
-Na+
-K+
-Cl-
-HCO3-
-albumin?
-Na+: 140
-K+: 2.5 - 4.0
-Cl-: 90 - 100
-HCO3-: 24
-albumin: 8 - 20