Lesson 1: Renal Anatomy & Physiology and Function Test Flashcards
The human body contains approximately how many nephrons per kidney?
1 to 1.5 million
This is located adjacent to the ascending and descending loops of Henle in juxtamedullary nephrons and in this area, the major exchanges of water and salts take place between the “Blood” and the “Medullary Interstitium”
Vasa recta
2 Types of Nephrons
Cortical Nephrons:
- 85% of nephrons
- Cortex
- Removal of waste products and reabsorption of nutrients
Juxtamedullary nephrons
- Have longer loops of Henle
- Medulla
- For concentration of urine
This supplies blood to the kidney
Renal artery
What percentage of blood do human kidneys receive from the heart?
25%
Blood enters the capillaries of the nephron through the?
Afferent arteriole
Before returning to the renal vein, blood from the efferent arterioles enters the _________ and _________ and flows slowly through the cortex and medulla of the kidney close to the tubes
peritubular capillaries and vasa recta
These surround the proximal and distal convoluted tubules, providing for the:
Proximal convoluted tubule = immediate reabsorption of essential substances from the fluid
Distal convoluted tubule = final adjustment of urinary composition
Identify the capillaries
Peritubular capillaries
Based on the average body size of 1.73m^2, what is the:
Total Renal Blood Flow:
Total Renal Plasma Flow:
Total RBF: 1200 mL/min
Total RPF: 600-700 mL/min
Normal value fors renal blood flow and renal function tests depend on?
Body size
The glomerulus consists of a coil of approximately ____________
8 capillary lobes
The walls of the capillary lobes are referred to as?
Glomerular Filtration Barrier
The glomerulus is located within ___________, which forms the beginning of the renal tubule
Bowman’s capsule
The pores increase capillary permeability but do not allow the passage of large molecules and blood cells, these are referred to as?
Fenestrated endothelium
Plasma filtrate must pass through 3 Glomerular Filtration Barrier Cellular Layers which are?
Capillary Wall Membrane
Basement Membrane (Basal Lamina)
Visceral Epithelium of Bowman’s Capsule
Which serves as a “non-selective filter” of plasma substances? MW: <70,000
Glomerulus
Further restriction of large molecules occurs as the filtrate passes through the basement membrane and the thin membranes covering the filtration slits formed by the intertwining foot processes of the _________ of the INNER LAYER of the Bowman’s capsule
Podocytes
The primary protein associated with renal disease
Albumin
Renal Blood Flow (7)(RAGE PVR)
Renal artery
Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries
Vasa recta
Renal vein
What monitors the blood pressure and plasma sodium content?
Juxtaglomerular apparatus which consists:
JG Cells = afferent arteriole
Macula densa = DCT
An autoregulatory mechanism within the juxtaglomerular apparatus maintains the glomerular blood pressure at a relatively constant rate, regardless of fluctuations in systemic blood pressure by what action?
By changing the size of the afferent and efferent arterioles
When blood pressure drops, this action prevents a marked decrease in blood flowing through the kidney, thus preventing an increase in the blood level of toxic waste products.
Afferent arterioles:
Efferent arterioles:
Drop in BP
Afferent: Dilation
Efferent: Constriction
This system regulates the blood flow to and within the glomerulus
RAAS
If not for the ___________, all routine urines would have positive readings on reagent strips for protein and albumin
Shield of negativity
When blood pressure increases, what action takes place between the afferent arterioles and efferent arterioles?
Increase in BP
Afferent: Constriction
Efferent: Dilation
Renin is produced by what cells?
Juxtaglomerular cells
Urinary Filtrate Flow (10) (BPDAD CRUBU)
Bowman capsule
Proximal CT
Descending LH
Ascending LH
Distal CT
Collecting duct
Renal calyces
Ureter
Bladder
Urethra
Angiotensin II corrects renal blood flow by? (3)
Causing vasodilation of afferent arterioles and constriction of efferent arterioles
Reabsorption of Sodium and Water in the PCT
Release of Aldosterone (sodium-retaining hormone from Adrenal cortex) and ADH (from the Hypothalamus)
Every minute, approximately 2-3 million glomeruli filter how much water-containing LMW substances?
120 mL
What is the specific gravity of the ultrafiltrate of plasma as it leaves the glomerulus?
1.010
The cellular mechanisms involved in tubular reabsorption are termed as?
Active and passive transport
Active Transport is responsible for the reabsorption of these substances in?
Glucose, amino acids, and Salts =
Chloride =
Sodium =
Glucose, AA, Salts = PCT
Chloride = Ascending LH
Sodium = DCT and PCT
Which part of the nephron is water unable to cross because its walls are impermeable to water?
Ascending Loop of Henle
Passive Transport is responsible for the reabsorption of these substances in?
Water =
Urea =
Sodium =
Water = PCT, DCT, Descending LH except for Ascending LH
Urea = PCT, Ascending LH
Sodium = Ascending LH
When plasma concentration of a substance that is normally completely reabsorbed reaches a level that is ABNORMALLY HIGH, the filtrate concentration exceeds the _____________ of the tubules, and the substance begins appearing in the urine
Maximal reabsorptive capacity (Tm)
Plasma renal threshold of GLUCOSE
160 to 180 mg/dL
The plasma concentration at which active transport stops is termed as?
Renal threshold
Tubular secretion serves two major functions (2)
Eliminating waste products not filtered by the glomerulus
Regulating acid-base balance through H+ secretion
Why can’t medications be filtered by the glomerulus?
They are bound to plasma proteins
This selective reabsorption process serves to maintain the osmotic gradient of the medulla
Countercurrent mechanism
Major site of removal of nonfiltered substances is in the?
Proximal convoluted tubule
The buffering capacity of the blood depends on what ions that are readily filtered by the glomerulus and must be returned to the blood expediently to maintain proper pH
Bicarbonate ions (HCO3-)
In the PCT, ammonia is produced from the breakdown of the amino acid ________
glutamine
Ammonia reacts with H+ to form the ________
ammonium ion (NH4+)
A disruption in the secretory functions can result in the inability to produce an ACID URINE, this condition is called?
Metabolic acidosis or Renal Tubular Acidosis
The standard tests used to measure the filtering capacity of the glomeruli are termed as?
Clearance Tests
Clearance test measures the rate in _____________ at which the kidneys are able to remove (to clear) a filterable substance from the blood
milliliters per minute (mL/min)
True or False
To ensure that the glomerular filtration is being measured accurately, the substance analyzed must be one that is NEITHER reabsorbed nor secreted by the tubules
True
Other factors to consider in selecting a clearance test substance include what?
Stability of substance in urine during a 24-hour collection period
Consistency of the plasma level
Substance’s availability to the body
Availability of tests to analyze the substance
How much of filtered urea is reabsorbed?
40%
What are examples of PRIMARY substances used in clearance tests?
Creatinine
Beta2-microglobulin(B2M)
Cystatin C
Radioisotopes
In the earliest Glomerular Filtration Tests, why was urea measured?
Because of its presence in all urine specimens
It is a test that requires an infused substance
Exogenous procedure
It is a polymer of fructose that is an extremely stable substance that is neither reabsorbed nor secreted by the tubules
Inulin
It was the original reference method for clearance tests
Inulin
Creatinine is produced enzymatically by ___________ from creatinine, which links with ATP to produce ADP and energy
Creatinine phosphokinase
These are medications that inhibit tubular secretion of creatinine, thus causing serum levels that are falsely low
Gentamicin
Cephalosporins
Cimetidine (Tagamet)
True or False
Accurate results of Creatinine Clearance depends on the accurate completeness of a 24-hour collection
True
True or False
Bacteria will break down urinary creatinine if specimens are kept at RT for extended periods
True
Newer methods that do not require the collection of time (24-hour) urine specimens have been developed using just:
Serum creatinine
Cystatin C
B2M values
The results of these are reported as?
Estimated Glomerular Filtration Rate (eGFR)
What are the units used for:
Volume (V)
Urine creatinine concentration (U)
Plasma creatinine concentration (P)
V = mL/min
U = mg/dL
P = mg/dL
NKDEP stands for?
National Kidney Disease Education Program
The urine volume is calculated by dividing the number of milliliters in the specimen by the number of minutes used to collect the specimen = (V)
Ex: Calculate the urine volume (V) for a 2-hour specimen measuring 240mL
240 mL / 120minutes = 2 mL/min
The formula used most frequently in eGFR is called?
Modification of Diet in Renal Disease (MDRD) study
Standard formula for plasma cleared per minute (C)
C = UV/P
Why are eGFRs not accurate for pediatric patients?
Because they are calculated for an average body size
Why are eGFR equations superior to serum creatinine alone?
Because they include variables for race, gender, and age
eGFR results are recommended to be reported as?
Results are lower: <59 mL/min
Results are higher: > or equal to 60 mL/min
If a patient drinks more water, does this increase or decrease the specific gravity of the urine?
Decrease
eGFR results are shown to be most accurate when results are?
Lower than 60mL/min
True or False
An advantage of Cystatin C is that it muscle dependent
False, Cystatin C is independent of muscle mass
It is a good procedure for screening and monitoring GFR
Cystatin C
Indicate if Glomerular or Tubular Disorder
Increased B2M in the blood
Low levels of B2M in the urine
Glomerular Disorder
Cystatin C is a small protein that is produced by?
All nucleated cells
It dissociates from human leukocyte antigens at a constant rate and is removed rapidly from the plasma by glomerular filtration
Beta2-Microglobulin
What can be used to distinguish disorders of the kidney as either “Tubular” or “Glomerular”
Beta2-Microglobulin
For radionucleotides, what are examples of exogenous markers used as radioisotopes (3)
125I-iothalamate
Chromium-51 ethylene-diamine-tetra-acetic acid (51 Cr-EDTA)
Technetium-99-labeled diethylene-triamine-pentaacetate (99-Tc-DTPA)
It is often the first function affected in renal disease
Tubular reabsorption
True or False
A urine osmolality reading of 800mOsm or higher is normal
True
This is a test for specific gravity where patients were DEPRIVED OF FLUIDS for 24 hours before SG is measured
Fishberg Test
This is a test for specific gravity wherein it compared the volume and specific gravity of urine specimens collected during the DAY and at NIGHT to evaluate concentrating ability
Mosenthal Test
Tests to determine the ability of the tubules to reabsorb the essential salts and water that have been non-selectively filtered by the glomerulus are called?
Concentration test
It measures ONLY the number of particles in a solution
Osmolality
A type of diabetes insipidus where the patient is not capable of producing ADH (Hypothalamic problem)(Normal results)
Neurogenic diabetes insipidus
A type of diabetes insipidus where the patient’s renal tubules are not responding to ADH(Kidney Problem)(Abnormal results)
Nephrogenic diabetes insipidus
A urine-to-serum ratio (U:S ratio) of 3:1 or greater or a urine osmolality of 800 mOsm or greater indicates what state of tubular reabsorption?
NORMAL Tubular Reabsorption
It measures BOTH number and density of the particles in a solution
Specific gravity
An instrument that determines the freezing point of a solution by supercooling a measured amount of sample to approximately 27C
Freezing-Point Osmometers
In freezing point osmometers, what is the approximate temperature used for supercooling a solution?
27C
Freezing-Point Osmometer
It is a temperature-sensitive probe in which resistance decreases as temperature increase, measures the temperature increase which corresponds to the freezing point of the solution, and the information is converted into milliosmoles
Thermistor
1 mol (1000 mOsm) of a non-ionizing substance dissolved in 1kg of water is known to lower freezing point to?
1.86C
Vapor Pressure Osmometers
If there is a decrease in dew point, what happens to the vapor pressure?
It will also decrease because the solute parallels therefore providing a measure of this colligative property
It is the temperature at which water vapor condenses to a liquid
Dew point
A typical person excretes approximately how much acid per day?
70 mEq/day
Factors to consider because of their influence on true osmolarity readings
Lipemic serum
Lactic acid
Volatile substances (ethanol)
It is a test used to determine the ability of the kidney to respond to the body’s state of hydration
Free Water Clearance
Reference serum osmolality values
275 to 300 mOsm
Ratio of Urine to Serum Osmolality
Normal Random Conditions:
After Controlled Fluid Intake:
Normal Conditions = 1:1
After Controlled Fluid Intake: 3:1
Vapor Pressure Osmometers are used primarily to analyze serum and sweat microsamples for disorders not related to renal function, such as _________
Cystic fibrosis
Alkaline tides that affect the urine acidity occur at?
Shortly after arising
Postprandially at 2pm-8pm
The test most commonly associated with tubular secretion and renal blood flow is the PAH test or also known as?
p-aminohippuric acid test (PAH)
The acid excreted by a person per day is in the form of?
Titratable acid (H+)
Hydrogen Phosphate (H2PO4-)
Ammonium ions (NH4+)
Historically, what test was used to evaluate urine pH, titratable acidity, and urinary ammonia.
(Hint: This dye is excreted)
Phenolsulfonphthalein Test = PSP Test
The lowest pH is found in day or night?
Night
Urine pH, titratable acidity, and urinary ammonia measurements can be used to determine the defective function of PCT or DCT.
The tests can be run simultaneously on either fresh urine specimens or those preserved with ________ and collected at 20-hour intervals from patients who have been primed with an acid load consisting of oral ammonium chloride
Toluene
