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63 Cards in this Set

  • Front
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Renal Functions

1. Regulation of body fluid osmolality & volume


2. Regulation of electrolyte balance


3. Regulation of acid-base balance


4. Excretion of metabolic & foreign substances


5. Production & secretion of hormones

Which hormones are produced/secreted by renal system?

Renin


Prostaglandins/kinins


1,25-dihydroxyviamin D3 (calcitriol)


Erythropoietin

Renal circulation - Name all vessels that blood goes through starting with the aorta


(bolded names = arteries)

Aorta - Renal artery - Segmental artery - Interlobar artery - acrucate artery - cortical radiate artery - afferent arteriole - glomerular capillaries - Efferent arteriole - Peritubular capillaries & vasa recta - cortical radiate vein - arcuate vein - interlobar vein - renal vein - inferior vena cava

Peritubular capillaries can also branch into...

Cortical radiate and arcuate veins directly

Nephron parts, starting at glomerulus

Bowman's capsule - Proximal convoluted tubule - Henle's loop (thin descending) - Henle's loop (thick ascending) - Distal convoluted tubule - Connecting tubule - Collecting duct

Types of nephrons and their description

1. Juxtamedullary nephron - Only present at boundary btw cortex and medulla, loops go deep into medulla, *concentrate urine


2. Cortical nephron - Present mostly in cortex, henle's loop touches outer zone of medulla

Type of nephrons (in %) found in:


Dogs/cats


Pigs


Humans

100% Juxtamedullary in dogs/cats


3% Juxtamedullary in pigs


14% Juxtamedullary in humans

Basic Renal Processes

1. Golmerular filtration


2. Tubular Reabsorption


3. Tubular Secretion

Blood pressure in:


1. Renal artery


2. Afferent arteriole


3. Glomerulus


4. Efferent arteriole


5. Peritubular capillaries


6. Renal vein

1. 100 mmHg


2. 100-50 mmHg


3. 50 mmHg


4. 50-20 mmHg


5. 20 mmHg


6. 10 mmHg

Tubular reabsorption - locations and what happens at each

PCT - Nutritents and H20 reabsorbed


Thin Descending Limb - H20 reabsorbed


Thick Ascending Limb - NaCl reabsorption


DCT - Na and H20 reabsorption


CT - H20 reabsorption

Solute concentration in thin descending limb vs. thick ascending limb

Thin - High solute concentration (~600-900mOsm/l)



Thick - Low solute concentration (~100mOsm/L)

Assessments of renal function

1. Serum biochemical tests


2. Urine analysis


3. Renal Clearance

Serum biochemical tests measure what?

Blood urea nitrogen (simple, not very accurate)


Creatinine


Electrolyte concentrations

Urine analysis measures what?

Volume


Specific gravity


Colour


pH


Electrolytes, enzymes and proteins

Renal Clearance measures what?

Glomerular function: Glomerular Filtration Rate



Tubular function: 1) Renal clearance rate, 2) Fractional clearance of electrolytes

Formula for Amount excreted in Urine

Amount excreted in urine =


Amount filtered (thru golmeruli into PCT)


- Amount reabsorbed (into renal vein)


+ Amount secreted (into tubular luminal fluid)

1st step in urine formation

Ultrafiltrate of plasma by glomeruli

Glomerular Filtration Rate (GFR) definition

Volume of Plasma filtered by the glomerulus per unit time


ml/min/kg

GFR should be...

Essentially protein free

Ultrafiltration driven by?

Starling forces across glomerular capillaries and into bowman's space

Glomerular filtration barrier formula

Glomerular filtration barrier = capillary endothelium + basement membrane + filtration slits of podocytes

What cells line the DCT

Macula Densa Cells

Which cells are found in the Mesangial Region

Lacis Cells (aka Extraglomerular mesangial cells)

Capillary endothelium is ___________ in the glomerulus

Fenestrated

Glomerular Filtration Pressures

Plasma Colloid Pressure - 32 mmHg


Glomerular Hydrostatic Pressure - 60 mmHg


Capsular Hydrostatic + Colloid Pressure - 18 mmHg


Filtration Pressure - 10 mmHg

Filtration pressure equation

Puf - Ultrafiltration P
Pgc - Glomerular Capillary hydrostatic P
acg - Glomerular Capillary Oncotic P
Pbc - Hydrostatic P
abc - Oncotic P

Puf - Ultrafiltration P


Pgc - Glomerular Capillary hydrostatic P


acg - Glomerular Capillary Oncotic P


Pbc - Hydrostatic P


abc - Oncotic P

GFR equation

Kf - Ultrafiltration coefficient (filtration barrier permeability x glomerular surface area available for filtration)

Kf - Ultrafiltration coefficient (filtration barrier permeability x glomerular surface area available for filtration)

What does ATP and Adenosine do to GFR (include steps leading up to change in GFR)

Vasoconstriction of afferent arteriole


Increased resistance, Decreased renal blood flow


Decreased Capillary BP (Pgc)


Decreased GFR

What does ANP and Glucocorticoids do to GFR (include steps leading up to change in GFR)

Vasodilation of afferent arteriole


Decreased resistance, Increased RBF


Increased Capillary BP (Pgc)


Increased GFR

What does ANG-2 initially do to GFR (include steps)

Vasoconstriction of efferent arteriole


Increased resistance, Decreased RBF


Increased Capillary BP (Pgc)


Increased GFR

What does NE, EPI, ANG-2, ADH and Endothelin do to GFR (include steps)

Vasoconstriction of afferent arteriole AND efferent arteriole


Increase resistance, Decrease RBF


Decrease Capillary BP (Pgc)


Decrease GFR

What does Dopamine, NO, kinins, PGE2, and PGI2 do to GFR (include steps)

Vasodilation of both afferent and efferent arterioles


Decrease resistance, Increase RBF


Increase Capillary BP (Pgc)


Increase GFR

What is inulin used for?

Marker to estimate renal clearance

Glomerular filtration barrier restricts filtration of molecules on the basis of __________ and _______________

Size


Electrical Charge

Permeability of cations, neutral, and anions (relative to one another)

Cations > neutral > anions

Which substances have extremely low filtrate/filtrand values? Why?

Hemoglobin and Serum Albumin



High molecular weight and radius

Which substances have low filtrate/filtrand values? why?

Myoglobin and Egg Albumin



High molecular weight and radius (not as high as hemoglobin and serum albumin though)

Which substances have a filtrate/filtrand of about 1? why?

Water, urea, glucose, sucrose, inulin


Lower molecular weight and radius



*Inulin is 0.98 Filtrate/Filtrand

Pathological Factors affecting GFR

1. Kidney diseases


2. Inverse relation between alpha GC and GFR


3. Inverse relation between Pbc and GFR

Why does kidney disease affect GFR

Decrease Kf by decreasing number of filtering glomeruli and thus GFR decreases

What can over come kidney disease effects?

Drugs/Hormones that dilate glomerular arterioles and thereby increase Kf

Example of kidney disease and what does it do?

Glomerulonephritis (*chronic)



Cause decrease GFR due to decrease in Kf which leads to an increase in proteinuria

What can cause a lowered GFR when looking at the inverse relation between aGC and GFR?

Acute obstruction of the urinary tract (kidney stone)



Backpressure pushes hydrostatic pressure up

Pbc is affected by?

Changes in protein metabolism occurring in extra-renal organs

High protein diets result in?

Increased renal blood flow and GFR

GFR measurement marker characteristics

1. Freely filtered by glomerulus


2. Not absorbed/secreted by nephron


3. Not metabolized/produced by kidney


4. Does not alter GFR per se

Markers used for GFR measurement

1. Inulin


2. Creatinine


3. Technetium (radioisotope) or Iohexol (contrast agent)

Inulin as a GFR measurement marker


(include limitations)

Gold standard


Limitation: expensive and impractical bc requires catheterization and timed sampling

Creatinine as a GFR measurement marker


(include limitation)

Most commonly used - muscle produces creatinine at a constant rate proportional to muscle


Limitations: secreted in PCT (~10% error), not useful at all in birds

Definition of renal clearance

Amount of plasma that needs to be filtered to account for the amount of substance present in urine every minute

Renal Clearance formula

Cx: volume plasma cleared
Ux: urine concentration
dV/dt: volume urine collected in a time period
Px: plasma concentration

Cx: volume plasma cleared


Ux: urine concentration


dV/dt: volume urine collected in a time period


Px: plasma concentration

GFR inulin clearance formula

*if using creatinine, just substitute creatinine for inulin

*if using creatinine, just substitute creatinine for inulin

Renal Plasma Flow measured by?

Clearance of p-aminohippuric acid (PAH)

Why is PAH used?

Not produced by body, so has to be infused


Is filtered by glomeruli, secreted by tubules and excreted in urine

Renal Plasma Flow (RPF) formulas

Define filtration fraction (FF). Formula? Normal values?

Portion of plasma that is filtered



FF = GFR / RPF



0.15 to 0.20

A 50% loss in functioning nephrons, decreases the GFR by ______%.. Why?

only 20-30%



Compensatory action of remaining healthy nephrons

Fractional Excretion (FE) and Fractional Reabsorption (FR) rate equations

What does Autoregulation do?

Maintains a nearly constant GFR when MAP is between 80-180 mmHg

Mechanisms of Autoregulation

Myogenic Mechanism



Tubuloglomerular Feedback Mechanims

Myogenic Mechanism when MAP increases

Cells involved with tubuloglomerular feedback

Macula densa cells


Juxtaglomerular cells


Lacis cells in mesangial region

Steps of Tubuloglomerular feedback starting with and increase in GFR

1. Increase in GFR


2. Tubular flow increases


3. Flow past macula densa increases


4. Paracrine factors diffuse from macula densa to afferent arteriole (ATP, Adenosine)


5. Decrease in renin and Increase in ATP release


6. Afferent arteriole constriction = increased resistance = decreased GFR