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What are the generalized functions of the renal system?
regulate water, electrolytes, BP, ECF, RBC production, acid-base balance, vitamin D production and calcium/phosphate balance
- excrete waste and foreign substances
If calcium and phosphate are not regulated correctly in the renal system then what can happen?
body retains the ion
body rids of the ion
What is the normal pH of urine?
Does urine reflect the pH of the blood?
In the case of acidosis, the kidneys will rid the body of acid and retains ________________
HCO3 (base) to buffer the pH
In alkalosis in which the kidney rid the body of __________ and retains ____________ to drive the pH down.
hormone secreted by the kidney; it raises blood pressure by influencing vasoconstriction (narrowing of blood vessels)
What does the renin-angiotensin-aldosterone system do?
Regulate blood pressure and sodium potassium balance
What does calcitriol do?
absorbs Ca2+ from the GI tracband builds bones
What is needed to build bones to prevent rickets?
vitamin D3 (calciterol)
What hormone stimulates RBC production?
Vitamin ______ enhances the intestinal absorption of calcium, iron, magnesium, phosphate and zinc.
What can hormones tell us through urinalysis?
if there is a lack of an ion like calcium. The body secretes hormones to help conserve the ion
Why is erythropoietin important in people that have bone marrow cancer?
because erythropoietin is what is needed to make new bone marrow
What is the purpose of a metanephric kidney?
to retain water
What do superficial (cortical) nephrons do?
supply O2 and nutrients to tissues
serve as a pathway for reabsorption of substances.
more dilute urine
juxtamedullary nephrons are responsible for?
nephrons with well-developed loops of Henle that extend deeply into the renal medulla and are responsible for oncentrating urine
What would happen to blood viscosity if the juxtamedullary nephrons did not work?
blood viscosity would be very high
What is a brush border used for?
What important structure is on the basolateral membrane?
Where does a lot of absorption occur?
Where are a lot of Na/K ATPease located in the renal system?
thick ascending portion of loop of hence
When a tube does not have a brush border or basolateral membrane what can we assume?
the it serves as a conduit
What protein is important for diagnosis of kidney issues?
Where is tamm-horsefall protein excreted from?
thick ascending loop of henle
What do principle tubule cells do?
reabsorb NaCl and H2O but secretes K+
What do intercalated tubule cells do?
maintain acid-base balance with high amounts in the mitochondria
Alpha intercalated cells do what?
secretes H+ (reabsorbs HCO3-)
Happens when there is too much acidity in the blood
Beta intercalated cells do what?
secretes bicarbonate HCO3- (reabsorbs H+)
happen when there is too much bicarbonate in the blood
What is the renal corpuscle composed of?
bowmans capsule, glomerulus, afferent and efferent arterioles
What does the renal corpuscle do?
What is the renal tubule composed of?
proximal convoluted tubule, loop of henle, distal convoluted tubule
What does the renal tubule do?
reabsorption and secretion
What kind of capillaries are in the glomerulus?
What does the filtration barrier consist of?
1. endothelium of the capillary (fenestrated),
2. the basement membrane and
3. podocyte or foot process from the Bowman's capsule.
If RBCs and WBCs are seen it urine what does it mean?
glomerularnephatis, the kidney is not filtering well
Why do substances that are large and negatively charged usually not filter out of the nephron?
because the capillaries are also negatively charges and therefore repel it
What is the basement membrane composed of?
Porous matrix of negatively charged proteins
Where are podocytes located and what do they do?
they are on the outside of the glomerular capillaries and help control what can and can't go through to the bowmans space
•Restriction of filtration is based on _______ and _______________
size (smaller more favorable) and charge (positive favorable)
What are mesangial cells?
contractile cells that help regulate glomerular filtration
What do mesangial cells secrete?
prostaglandins and pro-flammatory cytokines.
Where are lacis cells located and what do they do?
near the efferent arteriole and help secrete erythropoietin if the urine is too watery
The kidney has NO ___________________ innervation
What sympathetic neurotransmitter increases renin?
Norephrine enhances reabsorption of what?
Na+ and water
Norepinephrine causes vaso__________
vasoconstriction (alpha receptors)
What are dopamines two effects on the kidney?
causes naturisis (excretion of sodium) and vasodilation
might depress renin
What can lead to acute tubular necrosis (ATN) if uncorrected?
vasoconstriction of blood vessels (like when someone has a heart attack or decreased CO)
Renin secretion _____________ blood pressure (increases or decreases)
Theoretically an overactive sympathetic nervous system can lead to what?
glomerular capillaries are a ________ pressure system
Peritubular capillaries are a ______ pressure system
What 3 factors is the excretion rate dependent on?
1. rate of filtration
2. rate of reabsorption
3. rate of secretion
What is ultrafiltrate composed of?
salts, organic molecules and amino acids is similar to plasma
NO cellular elements, and very little protein
What is the main force that favors filtration?
Pgc (glomerular capillary pressure)
What two forces oppose filtration?
Hydrostatic pressure of fluid in the Bowman's space (PBS)
and oncotic pressure in the glomerular capillary (πGC)
What is the normal net filtration around?
Why is oncotic pressure of the bowmans space usually not important?
because it is usually 0! It only becomes a problem if protein is filtered into the bowmans space like in glomerneuroitis
Equation for ultrafiltration
Puf = Pgc - (Pbs + PIgc)
Where are the major sites to control renal blood flow and why?
afferent and efferent arterioles because that is where most of the resistance is
GFR = Kf x net filtration pressure
What is Kf?
filtration coefficient, property of intrinsic permeability and glomerularsurface area
What can change GFR?
1. Kf (diseases and properties of the molecule)
What increases GFR?
increase in arterial BP
increase in efferent arterial tone
increase plasma flow rate
decrease in afferent arteriolar tone (more "blood" in glomerular capillaries)
Vasodilation of the afferent arteriole results in what?
increase in Pgc and increase in GFR
Vasoconstriction of afferent arteriole results in what?
decrease Pgc and decrease in GFR
Vasodilation of EFFERENT arteriole results in what?
decrease Pgc and decrease GFR
Vasconstriction of EFFERENT arteriole results in what?
increase Pgc and increase GFR
Increase in BP results in what?
transient increase in Pgc and GRF
Decrease in BP results in what?
transient decrease in Pgc and GFR
Vasodilation causes renal blood flow to? (increase or decrease)
Vasoconstriction causes renal blood flow to? (increase or decrease)
How much cardiac output do the kidneys receive?
What would happen with a decrease renal blood flow such as what would happen with cardiogenic shock?
Death to the nephrons a condition called acute tubular necrosis and if enough of these nephrons are destroyed the patient can escalate into renal failure.
a measure of the disappearance of a substance from the circulation. In other words how much is cleared from the body.
Clearance of what nearly equals renal plasma flow?
the BEST estimate of renal plasma flow (and with knowledge of hematocrit renal blood flow) would be the renal clearance of what?
para-aminohippuric acid (PAH)
What would happen if the right renal artery has stenosis?
The majority of blood flow would go through the left kidney...it would be working a lot
Normal (resting) blood flow
1.2 L/min (20-25% of cardiac output)
Normal (resting) plasma flow
650 ml/min (measured by PAH clearance)
MAP = 2DP +SP/ 3
If there is a low MAP how do the renal vessels react?
If there is a high MAP how do the renal vessels react?
GFR and RBF are autoregulated when mean arterial pressure (MAP) ranges between?
80 - 180 mmHg
What two mechanisms regulate the radius of the AFFERENT arterioles
myogenic response to arterial pressure
tubuloglomerular feedback (response to NaCl)
Tubuloglomerular feedback example and increase in GFR results in an increase in.............
an increase in GFR results in an increase in NaCl flow by macula dense, this results in the increase formation of ATP and adensosine which then causes vasoconstriction and a DECREASE in GFR
ATP and adenosine cause vaso__________ (constriction or diliation) in the kidneys on ________________ arterioles
In the absence of ATP and adenosine in the renal system what happens?
vasodiliation of afferent arteriole
____________________ enhances adenosine vasoconstriction
What blocks the vasoconstriction affects of adenosine?
How does the macula densa contribute to auto regulation?
a.Release vasoconstrictors (ATP or Adenosine)
b.Release vasodilators (NO)
norepinephrine and epinephrine cause vaso_______________ alpha1 adrenergic receptors on the ______________ arterioles
What hormone degrades catecholamines (norepiphrine and epinephrine) and regulates blood pressure?
What will stimulate the sympathetic nervous system in the kidneys?
a decrease in extracellular fluid volume
Angiotension II causes vaso__________
What arterioles do angiotensin II vasoconstrict?
afferent and EFFERENT
Endothelin is a vaso_________-
Does endothelin affect both afferent and efferent arterioles?
Why are prostaglandins important in the renal system?
they damp vasoconstriction due to angiotensin II and the sympathetic nervous system?
What are the two things that will slow down or stop the vasoconstriction from the SNS?
renalase and prostaglandins
What are the vasoconstrictors of the renal system?
sympathetic nervous system, angiotensin II, and endothelin
What are the vasodilators of the renal system?
prostaglandins, NO, bradykinin, and naturitic peptides
When there is a lot of stretching on the heart what is released?
ANP and BNP
What would cause excessive stretching on the heart?
increased preload from congestive heart failure
What do ANP and BNP do?
increase sodium (and water) excretion, decrease CO, decrease vascular resistance, decrease central venous pressure
What is used to screen for congestive heart failure?
What is a normal BNP level?
What do natriuretic peptides do at the kidney?
vasodiliate afferent arteriole, vasoconstrict efferent arteriole therefore increasing GFR and Pgc
What affect does histamine have on the kidneys?
decreases resistance in the afferent and efferent arterioles therefore increasing RBF
What affect does dopamine have on RBF?
increases it because it vasodiliates afferent and efferent arterioles
an increase ____________ in the urine may be seen- sign of glomerular toxicity.
an autoimmune distruction of the capsular basement membrane that destroys the filtration barrier and therefore spills albumin out
filtered load equation
GFR x plasma concentration
What two things can increase filtered load?
1. increasing the GFR
2. increase the plasma concentration of the substance in question
What can affect the kidneys reabsorption of a substance from the tubule fluid?
the number of transport molecules available on the epithelium of the PCT
Cx = Ux X V/ Px
Size correction equation
Clearance X 1.73/ BSA
What is used for the best estimate of GFR?
the clearance of inulin
Clearance ratio equation
Cx / inulin (or GFR)
If the clearance ratio is 1 what does that mean?
the clearance is equal to the GFR and the substance is filtered and not reabsorbed nor secreted
If the clearance ratio is less than 1 what does it mean?
the substance is not filtered (ie. Albumin) or the substance is filtered and is reabsorbed either partially or completely.
If the clearance rate is greater than 1 what does it mean?
the substance is filtered and secreted (ie., PAH)
In a normal individual what substance is filtered and then completely reabsorbed?
Which substance has the highest clearance PAH or inulin?
What is an index of kidney function?
What is used for the 2nd best estimate of GFR?
What percent of plasma does not enter into the glomerulus?
What is the normal filtration fraction?
Normal GFR in males
Normal GFR in females
A GFR lower than what signifies kidney disease?
A GFR lower than what signifies kidney failure :(
Normal creatine plasma level
< or equal to 1.2 mg/dl
What creatine plasma level indicates renal disease and failure?
> 1.7 mg/dl
What are the two things someone would look at to see if a patient has kidney disease?
inulin or creatine in the urine and albumin in the urine
What is a normal blood urea nitrogen level?
< 20 mg/dl
A ratio of Bun to serum creatine that is > 20:1 indicates what?
renal failure :(
What other factors need to be considered when looking at BUN levels?
is the patient dehydrated, is there a urinary obstruction, starvation or high protein diets
Where does the majority of reabsorption occur in the renal system?
PROXIMAL CONVOLUTED TUBULE
What is the main function Na+/K+ ATPase found in the BL membrane in the renal system?
REABSOPTION.... that is why the PCT has a lot
How are GFR and surface area related?
What is the filtration coefficient dependent on?
surface area and permeability
How is Pgc and blood pressure related?
How are glucose and amino acids reabsorbed into the blood stream?
Na+ dependent secondary active transport
Where are intercalated cells located?
DCT and collecting ducts
Is the collecting duct part of the nephron?
Symporters, antiporters, and channels are examples of what kind of cellular passages?
tight junctions are an example of what kind of cellular passage?
What is absorbed in the FIRST half of the proximal tubule?
Na with HCO3, and Na with glucose, AA, phosphate and lactate
What is absorbed in the SECOND half of the proximal convoluted tubule?
Na with Cl
Where is the majority of chloride reabsorbed?
-Loop of Henle
-The proximal portion of the PCT
-The Distal part of the PCT
-The collecting duct
distal part of the proximal tubule
What indirectly places HCO3 into the interstium?
Na/H antiporter on the apical membrane because it is a byproduct of carbonic anhydrase
Is there a HCO3- channel or transport mechanism in the proximal tubule (apical)?
NO, the bicarbonate ion is a by-product for the hydrogen sodium exchange through the action of the carbonic anhydrase (CA)
Are Na+ and Cl- are transported transcellularly or paracellularly in the second half of the PCT?
How does Cl concentration increase from the proximal to distal part of the PCT?
Because the tube is dehydrating...most of the water, glucose, Na, have all been reabsorbed
How is Cl reabsorbed transcellularly?
How much water is reabsorbed in the PCT?
How do we equilibrate the transtubular osmotic gradient?
1. Move solutes into the blood
2. Move water from lumen to interstitial
Why do the cells in the PCT not explode with sodium?
Because of Na/K ATPease
Where is the majority of H20 absorbed?
Where are organic ions secreted from?
What drives the secretion of organic ions from the basolateral membrane into the tubule?
Why is there a slight positive charge in the distal PCT?
Because of the Na/H and Cl/H anti porter leaves more H in the tubule
How do organic cations get secreted?
passive diffusion from the negatively charged cell, and transporters
Reabsorption of NaCl occurs in both thin ________ and thick ___________ limbs
The _______________ limb does NOT reabsorb NaCl
What limb is impermeable to water?
Where is water reabsorbed in the loop of henle?
Where is NaCl reabsorbed in the loop of henle?
thick and thin ascending limb
The descending limb reabsorbs water from what gradient?
the gradient from the ascending limb where NaCl is reabsorbed
The thin ascending limb reabsorbs NaCl by? (passive or active)
The THICK ascending limb reabsorbs NaCl by? (active or passive)
active process Na+/K+ ATPase
Where is the macula densa located?
distal convoluted tubule
What does the macula densa do?
Senses NaCl in the distal convoluted tubule
When does the distal tubule and collection duct secreteof variable amounts of K+ and H+?
when hormones activate it to
The initial segment of the distal tubule absorbs Na+, Cl- and Ca+2 and is impermeable to _______
Where are principles cells and intercalated cells located?
Later Segments of Distal Tubule and Collecting Duct
ADH facilitates water ________________
Angiotensin II stimulates the reabsorption of what?
NaCl and water in PCT
What 3 things cause renin release?
Decrease in NaCl by macula dense, decrease blood pressure, and activation of SNS by kidney
Adosterone stimulates the secretion of what?
of K+ in DCT and CD
Aldosterone release is stimulated by hyp_________kalemia (hyper or hypo)
hyperkalemia (too much K in the blood)
What inhibits aldosterone release?
hypokalemia and natriuretic peptides
Overall what do ANP and BNP do?
diuresis, vasodilation, decrease the production of aldosterone, renin and ADH
Naturic peptides increase ________________ (GFR or RBF) and decrease _____________ (GFR or RBF)
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