Exam 1- kidneys Flashcards
what cells produce renin?
juxtaglomerular cells
what does the macula densa do?
regulates bloodflow into the kidney
what are the homeostatic functions of the kidney?
blood/water volume
osmolarity
electrolytes
acid/base
what does the kidney produce?
renin
glucose
calcitriol
erythropoeitin
what is the main ion in regulating water volume?
sodium
what metabolic wastes are removed by the kidneys?
urea
creatinine
uric acid
allantoin
bilirubin
what does renin do?
forms angiotensin II, which works to increase blood volume
what cells produce erythropoeitin?
interstitial fibroblasts close to peritubular capillaries and proximal tubule
what is the preferred gluconeogenic substrate of the kidney?
glutamine
what cells perform gluconeogenesis?
proximal tubule epithelial cells
how much of the cardiac output do the kidneys receive? why?
20%
they need to filter all of the blood: control composition and volume of body fluids rapidly
what is the functional unit of the kidney?
nephron
what capillaries are in the kidneys?
fenestrated
what are the three steps of urine formation?
filtration
selective reabsorption
selective secretion
what is the fluid in the tubule called (descending/ascending)?
filtrate
how much of the plasma moves into the filtrate?
20%
what are the two capillaries in the kidney portal system?
glomerular
peritubular
what does the glomerular capillary do?
filters plasma
what does the peritubular capillary do?
reabsorbs a lot of filtrate and secretes some things
what substances’ clearance rates can be used to measure GFR?
inulin
iohexal
creatinine
what fluid is in the Bowman’s space?
ultrafiltrate
what are the three layers of the glomerular filtration barrier?
fenestrated endothelium with glycoprotein coat
basement membrane with heparin sulfate
podocyte foot processes with nephrin (diaphragm) and glycoprotein coat
what two characteristics do mesangial cells exhibit?
contractile and phagocytic
what is GFR?
the volume of fluid filtered per minute from the glomerular capillaries into Bowman’s space
what does the filtration coefficient in Starling’s equation for GFR depend on?
permeability and surface area of filtration barrier
what is the main way to change blood flow in the kidneys?
changing arteriolar resistance or diameter
why does the hydrostatic pressure in the glomerular capillaries stay almost constant throughout the length of the capillaries?
entering efferent arterioles (high resistance compared to venules)
what is part of autoregulation for GFR?
stretch receptors in afferent arteriole smooth muscle
paracrine (tubuloglomerular feedback)
what regulates GFR that is not autoregulation?
SNS
Renin-Angiotensin-Aldosterone System
Atrial natriuretic peptide/beta natriuretic peptide
what is pressure diuresis?
high blood pressure leads to increased urine output and Na excretion
what is the juxtaglomerular apparatus made up of?
macula densa (senses flow filtrate and NaCl in distal tube)
juxtaglomerular cells (afferent arteriole- makes renin)
extraglomerular mesangial cells
what are the paracrine factors that regulate GFR?
Vasoconstrictors: Adenosine, ATP, Endothelin
Vasodilators: Prostaglandins, Nitric oxide
what does angiotensin II do to regulate GFR and RBF?
constricts efferent (preferentially) and afferent arterioles
decreases hydrostatic pressure in peritubular capillaries
what do Atrial Natriuretic Peptide and Beta Natriuretic Peptide do?
dilate afferent arterioles (more) and constrict efferent arterioles
increase renal blood flow and GFR (opposite of RAAS)
how does the sympathetic nervous system affect renal blood flow?
vasoconstriction
alpha-1 receptors on afferent arterioles predominantly
what is renal clearance?
volume of plasma cleared of a substance by kidneys per unit time
ml/min
what is inulin?
a fructose polymer that can be used to calculate GFR because it is freely filtered by the kidneys
gold standard GFR
what is the main substance used by clinics to calculate GFR?
creatinine
does drinking more water have any effect on GFR?
no
true/false: creatinine in blood changes according to muscle mass
true
what is the GFR measuring substance that does not require urine collection?
iohexal
what does azotemia usually indicate?
decreased GFR
what are the caveats to using plasma creatinine to estimate GFR?
- plasma creatinine is an insensitive marker to GFR (20% of normal) (sequential measurement more helpful)
- assays not standardized
- muscle mass affects creatinine
what is Symmetric Dimethylarginine (SDMA)?
new test for assessing GFR in cats and dogs
what is Filtered Load?
amount of substance filtered per unit time
is glucose found in a healthy animal’s urine?
no
what happens to sodium after it is filtered into the ultrafiltrate?
most of it is reabsorbed
what is special about potassium excretion in the kidneys?
after the initial glomerular filtration, more is added in the distal tubule
what is the Clearance Ratio?
clearance of any molecule compared to clearance of inulin (GFR)
what should the Clearance Ratio be for Na?
<1%
what does Angiotensin II during a mild decrease in MAP?
preferentially constricts efferent arterioles to decrease RBF and maintain GFR
what does Angiotensin II do during a hemorrhage?
constricts both efferent and afferent arterioles to have a small decrease in GFR and RBF
leads to decrease hydrostatic pressure peritubular capillaries: reabsorption water/ions, maintain ECF
what type of cells make up the outer wall of the Bowman’s Capsule?
simple squamous epithelium
what do mesangial cells produce?
mesangial matrix
several types cytokines
what detects flow rate in the macula densa?
primary cilia (monocilia)
which arteries enter the cortex in the kidney?
interlobular arteries
what does the vasa recta do?
reclaims water as urine is concentrated
what cells does the proximal convoluted tubule have?
tall cuboidal cells with basal nucleus
what does the Loop of Henle do?
moves salt and urea into interstitial space to create hypertonic interstitial space
where is transitional epithelium (urothelium) located?
renal calyx, renal pelvis
ureter
bladder
proximal urethra
what species have multilobar kidneys?
humans
cows
pigs
marine mammals
what is a renal infarct?
bloodflow is blocked to a section of kidney, leading a triangle to die
what is in the renal corpuscle?
Bowman’s capsule
glomerular tuft/glomerulus
mesangial cells
juxtaglomerular apparatus
what does macula densa do when flow rate or Na decrease?
secretes vasodilator
what is in the cortex histologically?
renal corpuscles (glomeruli)
convoluted and straight tubules
collecting tubules and ducts
what is in the medulla histologically?
straight tubules
collecting tubules and ducts
vasa recta
what areas are most vulnerable to ischemia and nephrotoxins?
areas with more mitochondria and cellular activity
what is the major site of reabsorption?
proximal convoluted tubule
what are the three sections of the loop of Henle?
descending limb (proximal straight tubule)
thin segment
thick ascending limb (distal straight tubule)
what do the loop of Henle and vasa recta establish?
osmotic gradient in medulla
what conserves Na via the Na/K ATPase and balances acid and base?
distal convoluted tubule
how can the collecting system be distinguished histologically?
clearly defined cell margins
clean lumenal space
2 types cuboidal epithelium
does the distal convoluted tubule have taller or lower cuboidal cells than the proximal convoluted tubule?
lower (also less distinct brush border or not visible)
what do the principal cells in the collecting system do?
insert aquaporins into membrane
respond to antidiuretic hormone
what do the intercalated cells in the collecting system do?
acid/base function
what is found in the inner medulla?
thin limbs loop of Henle
collecting ducts
vasa recta
what are the two types of nephrons?
cortical nephrons
juxtamedullary nephrons
where is most of the connective tissue found in the kidney located?
medulla
what does transitional epithelium (urothelium) produce?
antimicrobial molecules
what is in the tunica muscularis in ureters?
thin inner longitudinal
outer circular
extra longitudinal bundle at distal end
what is the outer layer of the bladder vs the ureter?
tunica serosa
tunica adventitia
what is the progression of epithelium in the female urethra?
urothelium proximally
stratified cuboidal
stratified squamous distally
what are the two regions of the canine male urethra?
prostatic
postprostatic
what are the three regions of the feline male urethra?
preprostatic
prostatic
postprostatic
where is the striated urethralis muscle located?
female: caudal 1/3 urethra
male: postprostatic region
what do the female cranial urethra and feline male urethra preprostatic have in common?
urothelium and smooth muscle is here (no smooth muscle cranially in male canine urethra)
what is the filtration fraction?
the amount of plasma presented to the kidneys that gets filtered through glomeruli (20-25%)
what are the morphological changes in the kidneys associated with aging?
loss nephron mass
glomerular sclerosis
loss of filtration surface area
what is proximal tubular P-aminohippurate (PAH) secretion mediated by?
organic anion transporters ((g)OAT)
why is creatinine not the gold standard for measuring GFR?
in primates there is secretion of it too
slightly off in dogs and cats
does a healthy kidney secrete sodium?
never ever
what is transcellular reabsorption?
two-step process which uses transporters or channels
what facilitates secondary active transport?
Na/K ATPase (pumping Na into blood)
what is the Na-coupled proximal tubular “symport” process used for?
amino acids
glucose
lactate, citrate, phosphate…
true/false: glucose is freely filtered and therefore glucose filtration is exactly proportional to the plasma concentration
true
what is renal threshold?
the minimal plasma glucose level at which excretion begins (no longer reabsorbing it all)
what receptors are used for capturing small proteins and peptides in the urine?
megalin and cubilin
how much insulin is excreted?
very little (almost 0)
what takes up secreted cations?
organic cation transporters in basal membranes in the tubular epithelium
is sodium reabsorbed in one or multiple parts of the nephron?
multiple
how is renal plasma flow estimated?
with the effective renal plasma flow (ERPF): amount of plasma cleared of p-aminohippuric acid (PAH) per unit time
what is true RPF?
ERPF/PAH renal extraction efficiency= 200/0.9 =~220 ml/min
what does the difference between the filtered load and the clearance of a substance indicate?
the net reabsorption and/or secretion
if the filtered load is greater than the excretion rate, what does this say about how the kidney is handling that drug?
it is reabsorbing the drug from the filtrate
what is the order of membranes/walls gone through for transcellular reabsorption?
- apical membrane
- epithelial cell cytosol
- basolateral membrane
- interstitial fluid
- capillary wall
what are the two types of reabsorption?
transcellular and paracellular reabsorption
what are the renal glucose transporters?
GLUT and SGLT (sodium glucose linked transporter)
where is most of the glucose reabsorbed?
S1 segment of the proximal tubule (SGLT2 and GLUT2)
what are two possibilities for glucose in urine?
hyperglycemia
defect in glucose reabsorption
how are amino acids reabsorbed?
secondary active transport
transcellular absorption in proximal convoluted tubules
how are organic cations secreted?
organic cation transporters (OCT), driven by negative membrane potential
what does a low pH urine do to weak acids?
protonates them and enhances their reabsorption
when is clearance of a weak acid highest (alkaline or acid pH)?
alkaline urine pH
how do most terrestrial animals excrete amino nitrogen?
allantoin
urea
what is articular gout?
uric acid crystal accumulation in joints and along tendons due to renal failure
where is urea transported in the nephron?
in most segments
how is urea transported?
simple or facilitated diffusion
what does urea do in the thin descending limb?
it is secreted up to 110% of the filtered load
where is impermeable to urea?
thin ascending limb
distal tubule
cortical an outer medullary collecting ducts
what is the last place urea is reabsorbed?
inner medullary collecting ducts
what does urea recycling contribute to?
corticopapillary osmotic gradient which is critical in determining the final osmolarity of urine
true/false: the urine pH can affect both solubility and reabsorption of weak acids and bases
true
why is sodium reabsorption in the kidney important?
driving force for reabsorption of organic substances and other ions
coupled with secretion of potassium and hydrogen ions
what is the major cation in ECF compartment?
sodium
what forces are in play in peritubular capillaries?
low hydrostatic pressure
high protein oncotic pressure
in what tubule is water and sodium reabsorption linked?
proximal tubule
where is the majority of sodium reabsorption?
proximal tubules and loop of Henle
what is transepithelial potential difference important in driving?
calcium and magnesium reabsorption
potassium secretion
how are solutes reabsorbed?
transcellular and paracellular
what is the major anion co-transported with sodium in the early proximal tubule?
bicarbonate (HCO3-)
why is HCO3- important?
critical buffer in maintaining physiological pH
what is the major anion co-transported with sodium in the late proximal tubule (S3)?
chloride (Cl-)
what happens to the [tubular fluid]/[systemic plasma] of Na+ as the filtrate goes through the proximal tubule?
stays the same at 1 because of isosmotic reabsorption
what happens to the [tubular fluid]/[systemic plasma] of glucose and amino acids as the filtrate goes through the proximal tubule?
decreases
is the ascending limb of the loop of Henle permeable to water?
no
what is the diluting segment of the nephron?
thick ascending limb and the distal convoluted tubule
what is transported in the thick ascending limb by the cotransporter?
Na+, K+, 2Cl-
where is the Na+-Cl- cotransporter?
early distal tubule
what is the major site of REGULATED tubular reabsorption?
late distal tubule and collection ducts
how does aldosterone affect epithelial Na+ channels (ENaC) in principal cells?
increases the channels
what is ECF potassium critical to?
excitability of nerves and muscle tissue
what is the main intracellular cation?
potassium
what does insulin do to Na/K ATPase?
increases its activity
what is the progression of K+ reabsorption and secretion after the glomerulus?
67% reabsorbed in proximal tubule
20% reabsorbed in thick ascending limb
reabsorbed in the distal tubule with low K+ diet (intercalated cells)
variable secretion in collecting ducts and distal convoluted tubule (principal cells)
what happens when there is a high K+ diet?
insulin pushes K+ into the cells via Na/K ATPase
secreted by principal cells through apical K+ channels
is aldosterone triggered by increased or decreases K+ intake?
increased
what organs are involved in calcium homeostasis?
intestine
bone
kidney
what stimulates calcium reabsorption at the distal tubule?
parathyroid hormone (PTH)
where is calcitonin produced?
thyroid parafollicular cells (clear or C)
what does calcitonin do?
decreases Ca++ in ECF
what do organic cation transporters do?
take up secreted cations in basal membranes of tubular epithelium
how does parathyroid hormone regulate phosphate excretion?
negatively regulates Na/Phosphate cotransporter which reabsorbs phosphate
what is the gold standard for measuring urine solute concentration?
osmolality
what is hyposmotic urine?
<300mOsm/L
more dilute than plasma
what affects specific gravity?
number of solute particles per liter of solution
color and turbidity
temperature
how does the refractometer measure specific gravity?
refractive index correlated against specific gravity
what is the term for hyperosmotic urine?
hypersthenuric
what part of the nephron is NOT permeable to water?
ascending thin limb through the distal convoluted tubule (proximal part)
what part of the nephron is under regulation for water reabsorption? what regulates it?
late distal convoluted tubule and collecting duct
antidiuretic hormone
what three things does antidiuretic hormone affect?
water permeability (principal cells) (aquaporins)
urea permeability (UT1)
Na/K/2Cl transporter (countercurrent multiplication)
what do the principal cells do?
reabsorb NaCl
secrete K+
variable water reabsorption
how does the loop of Henle act as a countercurrent multiplier?
deposits NaCl in the deeper interstitial fluid medulla
descending limb almost impermeable to ions/solutes
thick ascending limb almost impermeable to water
how is NaCl deposited in the interstitial fluid in the deeper medulla (passive vs active transport)?
passive through Na channels initially
thick limb: active transport via apical Na/K/2Cl transporter and Na/K ATPase
how is urea reabsorbed in the proximal tubule?
paracellularly without transporters
what drives secretion of urea in the thin descending limb?
high concentration urea in the interstitial fluid
without antidiuretic hormone, will more or less urea be excreted?
more urea
what does production of hypersthenuric urine require?
production of ADH
receptors for ADH
hypertonic interstitium: NaCl and urea
how and where is filtrate diluted to produce dilute urine?
thick ascending limb reabsorbs NaCl: hypotonic filtrate
early distal tubule reabsorbs NaCl by Na/Cl cotransporter
late distal tubule and collecting duct reabsorb more Na/Cl
what happens when less antidiuretic hormone (ADH) is secreted?
no aquaporins inserted into collecting ducts: impermeable
what dictates the relative proportion of water in the extracellular vs intracellular fluid?
gain or loss of sodium
what does infusion of isotonic saline do to the extracellular and intracellular fluids?
increases the amount of extracellular fluid and keeps the intracellular fluid the same
why does water follow sodium?
to keep the osmolarity constant, sodium and water are paired in their excretion for the most part
what does angiotensin II do with Na+ reabsorption in the proximal tubule?
stimulates Na/K ATPase and Na+-H+ exchange to reabsorb
what does angiotensin II stimulate in the distal tubule and collecting ducts?
Na channels and Na/Cl symporters
how does aldosterone promote potassium secretion?
inserts channels into apical lumen
Na/K ATPase (Na into cell, K into filtrate)
how does natriuretic peptide affect epithelial sodium channels (ENaC)?
decreases it to decrease Na reabsorption in the late distal tubule and collecting ducts
what does an increase in ECF volume mean for peritubular capillaries and Starling forces?
inhibit proximal tubule sodium reabsorption
what species secretes mucus in its proximal ureter and renal pelvis?
horse
what valve keeps the urine from backflowing?
vesicoureteral valves
what is needed to allow the bladder to fill without emptying?
sympathetic innervation: contraction internal urinary sphincter and relaxation of detrusor muscle
what opens the internal urinary sphincter?
high pressure from bladder (detrusor muscle contraction) and PNS input
what animals can get most of their water from metabolism?
desert rodents
what do bony fishes rely on more for eliminating excess or waste solutes?
tubular secretion
how can ammonia leave freshwater fish?
through their gills
what is the nitrogenous waste product of reptiles and birds?
uric acid
do birds have a urinary bladder?
no- urine enters cloaca
what percent of nephrons are functional at a given time?
10%
where do the juxtamedullary nephron renal corpuscles sit in reference to the cortex and medulla?
at the junction between
why is H+ transported into the filtrate? (sodium into cell, hydrogen into filtrate)
to combine with bicarbonate, to move CO2 and H2O across the membrane into lumen-lining cell
it then turns into H+ and bicarbonate again, bicarbonate moves into blood as buffer
what is the sequence of blood vessels between the renal artery and the renal vein?
renal artery
afferent arteriole
glomerular capillary
efferent arteriole
peritubular capillaries (in cortex)
vasa recta (in medulla)
renal vein
what is osmolality vs osmolarity?
osmolality: dissolved particles per kilogram
osmolarity: dissolved particles per liter
what is the range for normal blood pH?
~7.38-7.44
why is pH regulation important?
pH is tightly regulated to keep it appropriate because enzyme activity is dependent upon appropriate pH
what is alkalemia?
increased blood pH
what is acidosis?
physiologic condition that acts to increase H+ concentration
how can physiologic pH be maintained? (both healthy and not)
buffering
compensation
mixed acid-base abnormalities
do stronger acids have higher or lower pKa values?
lower
are weak acids or strong acids completely dissociated at physiologic pH?
strong acids
weak acids incompletely dissociated
how is the Henderson-Hasselbalch equation used?
to estimate pH of buffer solution
what is the primary extracellular buffer in blood/plasma?
bicarbonate
what does carbon dioxide form when dissolved in aqueous solutions?
carbonic acid
how are non-volatile acids dealt with?
metabolized or excreted
what are the sources of CO2 in the body?
carbohydrate oxidation
beta oxidation of fatty acids
does anaerobic glycolysis produce a volatile or non-volatile acid?
non-volatile (lactic acid)
what protein in blood does a lot of bufferimg?
hemoglobin
where is the phosphate buffer system most important?
intracellularly and in urine
what is the isohydric principle?
all the buffer systems acting on blood are in equilibrium vie their shared component, [H+]
therefore, we can evaluate acid-base balance by evaluating just one of the buffer systems
what enzyme catalyzes the conversion of CO2 and H2O to carbonic acid?
carbonic anhydrase
how can [H2CO3] be estimated?
with paCO2
what does bicarbonate concentration reflect?
metabolic regulation
what does PCO2 reflect?
respiratory regulation
where is most of the renal regulation of metabolic acid-base balance?
distal tubule and collecting duct
how is bicarbonate transported back into blood in the proximal tubule?
Na+/HCO3- symporter
what do A-intercalated cells do?
directly secrete H+ at the apical membrane
what do B-intercalated cells do to the blood?
acidify the blood by secreting HCO3- and reabsorbing H+
how does the liver alkalinize the blood?
gluconeogenesis using lactate
why does the renal ammonium excretion happen?
non-acidifying because preserves bicarbonate
glutamine converted to glutamate and ammonium, which is excreted in urine
what is metabolic acidosis?
decreased bicarbonate
what is respiratory alkalosis?
decreased CO2
what regulates ventilation?
central chemoreceptors in the medulla
peripheral chemoreceptors in the carotid and aortic bodies
what molecule is important in brain ECF pH changes?
CO2
what is titration for metabolic acidosis?
accumulation of an endogenous or exogenous organic acid (bicarb lost as it buffers acid, anion gap increased)
why is anion gap useful?
it helps to differentiate between titration and secretion acidosis
what is the traditional analysis for total carbon dioxide?
a strong acid is added to serum and the CO2 that is released is measured
if PCO2 is increased, what does it indicate?
respiratory acidosis
if total carbon dioxide is increased, what does is indicate?
metabolic alkalosis
is respiratory or metabolic compensation faster?
respiratory
what is compensation trying to do regarding the ratio of bicarbonate and PCO2?
trying to maintain the ratio at normal
what limits compensation for metabolic alkalosis?
the need for adequate oxygenation
what does addition of an organic acid do to the anion gap?
increases it
what can lactic acidosis result from?
increased anaerobic glycolysis
what are the types of lactic acidosis?
type A and type B
what does type A lactic acidosis result from?
oxygen deficit
what does type B lactic acidosis result from?
decreased metabolism of lactate and/or from increased lactate production
what do increased levels of ketones cause?
titration-type acidosis
what are three conditions that cause ketosis/ketoacidosis?
diabetes mellitus
starvation
bovine ketosis
can renal failure cause acidosis?
yes
what are three different options for an acidic blood pH?
secretion metabolic acidosis
titration metabolic acidosis
respiratory acidosis
does a larger anion gap indicate titration acidosis or secretion acidosis?
titration acidosis
what does ethylene glycol poisoning cause?
titration acidosis directly, and induce renal failure
what are the two causes of secretion metabolic acidosis?
urinary bicarbonate loss or GI bicarbonate loss
what leads to urinary bicarbonate loss (decreased reabsorption)?
renal tubular disease/renal tubular acidosis
compensation for chronic respiratory alkalosis
if a patient is acidotic, should their urine be aciduria or alkaluria?
aciduria
what is Fanconi’s syndrome?
a disease most common in basenjis where the renal tubules are not reabsorbing glucose, bicarbonate, sodium, potassium, urates, cystine/amino acids as they should
true/false: renal tubular acidosis is caused by a lower pH in the renal tubules and urine
false. it is caused by renal tubular dysfunction
where can renal tubular acidosis arise?
proximal tubule and/or distal tubule
true/false: proximal tubular acidosis is characterized by a defect in HCO3- reabsorption in the proximal tubules
true
what does distal tubular acidosis mean in terms of what is being secreted/absorbed incorrectly?
defect in H+ secretion
what are the causes of metabolic alkalosis?
increased base/buffer levels
loss of H+ (and Cl)
dehydration with Cl- loss and/or K+ depletion
why does vomiting lead to an increase in bicarbonate in the blood?
carbonic anhydrase produces both H+ and bicarbonate from CO2 and water, the H+ is being lost
what causes “alkaline tide”?
increased gastric acid production due to vomiting or eating (postprandial)
are pancreatic secretions into the duodenum high or low pH?
high
should patients with only metabolic alkalosis have a normal anion gap?
yes. bicarbonate gain balanced by chloride loss
does dehydration lead to metabolic alkalosis or acidosis on its own?
metabolic alkalosis (concentration bicarbonate increased)
what does hypoalbuminemia lead to? (alkalosis or acidosis)
alkalosis, unmeasured ion too
how can mixed metabolic conditions be recognized (HCO3 and TCO2 levels normal)?
high anion gap or high lactate level
what can cause a decreased anion gap?
artifact
decreased unmeasured anions
increased unmeasured cations
what does acidemia do to ionized calcium?
increases it because H+ competes with calcium for albumin binding sites
what does K+ do in alkalosis?
serum K+ may decrease (moves into cells as H+ moves out)
what does Stewart’s Theorem look at?
quantitative acid-base balance
what does an increased strong ion difference indicate?
metabolic alkalosis
what does a decreased strong ion difference indicate?
titration or secretion metabolic acidosis
how can titration vs secretion acidosis be distinguished?
look at the lactate and ketones
anion gap
strong anion gap
should a decreased strong ion difference have a low or high PCO2?
decreased PCO2
does dilution of blood cause a change in the strong ion difference?
yes, disproportionately affects sodium because its’ concentration is higher
what happens to most small proteins and peptides filtered through the glomerular capillary filter?
reabsorbed in proximal tubule via endocytosis
what pressure increases as you move down the glomerular capillary?
plasma oncotic pressure
what is myogenic control of blood flow in the kidneys?
autoregulation of GFR and RBF: stretch arterial walls leads to a reflex muscle contraction to decrease blood flow
what are the two main factors that alter glomerular filtration rate?
changes in renal blood flow
changes in glomerular capillary hydrostatic pressure
what is reabsorbed in the proximal convoluted tubule?
Na+
glucose
amino acids
phosphate
lactate
citrate
is urothelium permeable to water and salts?
no
for which solutes is the proximal tubule the MAJOR site of reabsoprtion?
glucose
phosphate
chloride
potassium
sodium
water
amino acids
what is the site of major reabsorption for magnesium?
thick ascending limb
what does parathyroid hormone regulate?
stimulates Ca++ reabsorption (thick ascending limb)
inhibits phosphate reabsorption (proximal tubule) (Na/Phosphate symporter)
what regulates epithelial Na+ channels?
aldosterone increases
atrial natriuretic peptide decreases
what does aldosterone do?
stimulates K+ channels
stimulates Na/K ATPase
stimulates Na+ channels
how do camels minimize their water loss?
raise their body temperature
dry feces and concentrated urine
why is blood in cartilaginous fishes isotonic with sea water?
high urea levels
what fish have a renal portal system?
bony fishes and freshwater fishes
can reptiles absorb water through the wall of the rectum or cloaca?
yes
does a reptile kidney have loops of Henle?
no
which glucose transporter is in the apical membrane versus the basolateral membrane?
apical membrane: sodium glucose linked transporters
basolateral membrane: glucose transporters
how is the sodium glucose transporter (SGLT-1 isoform) different in the late proximal tubule?
transports two sodiums per glucose instead of one
where are amino acids reabsorbed?
proximal convoluted tubules
where are anions and cations mainly secreted?
proximal tubules
transporters (OAT and OCT) in basal membranes
MDR1 and MDR2 in apical membranes for anions
are there urea transporters in the proximal tubule?
no
what are the postprostatic male layers of the urethra?
stratified squamous
stratum spongiosum
striated urethralis muscle
