chem unit 2 chapter 11
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Questions and Answers

Which of the following is NOT a characteristic of passive transport in renal tubular reabsorption?

  • Requires no energy
  • Requires carrier proteins (correct)
  • Water and urea are reabsorbed passively
  • Movement from high to low concentration

    • Tubular secretion is the movement of substances from the renal tubular cells into the peritubular capillaries.

    False (B)

    What is the primary function of tubular secretion in regulating the body's acid-base balance?

    Secretion of hydrogen ions

    The ______ is the concentration above which a substance cannot be totally reabsorbed by the kidneys and is excreted in the urine.

    <p>renal threshold</p> Signup and view all the answers

    Match the following nonprotein nitrogen compounds with their relative concentration in the body:

    <p>Blood urea nitrogen (BUN) = 45% Amino acids = 20% Uric acid = 20% Creatinine = 5% Creatine = 1%-2% Ammonia = 0.2%</p> Signup and view all the answers

    Which of the following is NOT a component of the urinary system?

    <p>Liver (D)</p> Signup and view all the answers

    The outer layer of the kidney is called the medulla.

    <p>False (B)</p> Signup and view all the answers

    What is the functional unit of the kidney?

    <p>Nephron</p> Signup and view all the answers

    The ______ arteriole carries blood into the glomerulus, while the ______ arteriole carries blood out.

    <p>Afferent, Efferent</p> Signup and view all the answers

    Match the following structures with their corresponding locations in the nephron:

    <p>Bowman's capsule = Beginning of the nephron Proximal convoluted tubule (PCT) = First segment of the renal tubule Descending loop of Henle = Part of the loop of Henle that descends into the medulla Ascending loop of Henle = Part of the loop of Henle that ascends back to the cortex Distal convoluted tubule (DCT) = Final segment of the renal tubule Collecting duct = Large duct that collects urine from multiple nephrons</p> Signup and view all the answers

    What is the primary function of the glomerulus?

    <p>Filtration of blood (C)</p> Signup and view all the answers

    The pressure in the glomerular capillaries is lower than the pressure in the rest of the circulatory system.

    <p>False (B)</p> Signup and view all the answers

    What is the role of the negative charge of the glomerular basement membrane?

    <p>It repels large, negatively charged molecules such as proteins.</p> Signup and view all the answers

    What is the reference range for BUN on a 24-hour urine?

    <p>12 to 20 grams/24h (D)</p> Signup and view all the answers

    A high ratio with an elevated C R suggests ______ or prerenal azotemia in addition to renal disease.

    <p>postrenal obstruction (azotemia)</p> Signup and view all the answers

    The most common BUN methodology utilizes the Glutamate Dehydrogenase (GLDH) procedure.

    <p>True (A)</p> Signup and view all the answers

    Match the BUN methodologies with their corresponding chemical reactions:

    <p>Urease = Urea + 2H2O ¾Urease ¾¾¾® 2NH4+ + CO3 -2 Berthelot’s Reaction = NH+4 + 5NaOCl + Phenol ¾Na ¾¾¾¾¾NaOH nitroprusside ® Indophenol blue + 5NaCl + 5H2O Nessler’s Reaction = 2Hgl2 + 2Kl + NH4+ ® NH2Hg2I3 + 4KI + NH4I Diacetyl or Fearon Reaction = Urea + Diacetyl + H2O ¾¾¾¾® Diazine + 2H2O Strong acid</p> Signup and view all the answers

    In the Berthelot’s reaction, what is the chromogen that is measured?

    <p>indophenol blue</p> Signup and view all the answers

    What is the reference range for BUN in mg/dL?

    <p>7-18 mg/dL (B)</p> Signup and view all the answers

    A high protein diet decreases BUN levels

    <p>False (B)</p> Signup and view all the answers

    In Nessler’s reaction, the addition of a ______ results in the formation of a yellow to orange brown compound with NH4+.

    <p>double iodide compound (2Hgl2 + 2KI)</p> Signup and view all the answers

    What are the three variables that influence B U N levels?

    <p>Urea concentration, Glomerular filtration rate (G F R), Level of hydration (D)</p> Signup and view all the answers

    In a dehydrated patient, the serum B U N is decreased and the urine B U N is increased.

    <p>False (B)</p> Signup and view all the answers

    What is azotemia?

    <p>An increased blood urea and other N P N compounds</p> Signup and view all the answers

    When the B U N levels are elevated due to problems in the kidneys, it is categorized as ______ azotemia.

    <p>renal</p> Signup and view all the answers

    Match the following types of azotemia with their corresponding causes:

    <p>Prerenal azotemia = Decreased renal blood flow, increased protein catabolism Renal azotemia = Kidney dysfunction, such as glomerulonephritis Postrenal azotemia = Obstructions in the urinary tract, such as tumors or stones</p> Signup and view all the answers

    The B U N:Creatinine ratio is typically within the range of 12:0 to 20:1 in individuals with renal disease.

    <p>False (B)</p> Signup and view all the answers

    What is the significance of an elevated B U N:Creatinine ratio?

    <p>It suggests a non-renal cause for the increased B U N level.</p> Signup and view all the answers

    Which of the following conditions could lead to Prerenal Azotemia? (Select all that apply)

    <p>Dehydration (A), Congestive heart failure (D)</p> Signup and view all the answers

    Creatinine clearance is a measure of the rate at which creatinine is filtered from the blood by the kidneys.

    <p>True (A)</p> Signup and view all the answers

    Why is creatinine a good indicator of glomerular filtration rate?

    <p>All of the above. (D)</p> Signup and view all the answers

    Creatinine clearance is calculated using the serum and urine creatinine levels, and the ______ volume.

    <p>urine</p> Signup and view all the answers

    Why is it important to correct creatinine clearance to an adult body surface area of 1.73 m2?

    <p>To account for variations in body size, particularly in small children, pediatric patients, and obese individuals.</p> Signup and view all the answers

    What is the most common source of error in creatinine clearance measurements?

    <p>Incorrect urine collection (A)</p> Signup and view all the answers

    Match the following variables with their corresponding units in the creatinine clearance equation:

    <p>U = mg/dL P = mg/dL V = mL/minute</p> Signup and view all the answers

    What is the reference range for creatinine clearance in males?

    <p>97-137 mL/minute</p> Signup and view all the answers

    The Dubois formula is used to calculate the surface area of the body.

    <p>True (A)</p> Signup and view all the answers

    What are the main causes of hyperuricemia?

    <p>Increased dietary intake, overproduction of uric acid, underexcretion of uric acid, specific enzyme defects (A), Cytotoxic chemotherapy, radiation therapy, malignancy, acute or chronic renal disease (C), All of the above (D)</p> Signup and view all the answers

    Primary gout is primarily associated with women in their 30s and 40s.

    <p>False (B)</p> Signup and view all the answers

    What are the symptoms of primary gout?

    <p>Arthritis (pain, inflammation of the joints), nephropathy, and nephrolithiasis</p> Signup and view all the answers

    The color change observed in the phosphotungstic acid method for measuring uric acid is from ______ to ______.

    <p>colorless</p> Signup and view all the answers

    Match the following terms with their corresponding definitions:

    <p>Hyperuricemia = High levels of uric acid in the blood Primary Gout = Inborn error of metabolism leading to gout Nephropathy = Kidney disease Nephrolithiasis = Kidney stones Allantoin = The product of uric acid oxidation by uricase</p> Signup and view all the answers

    Which of the following can precipitate gout attacks?

    <p>Alcohol (A), High-protein diets (B), Stress (C), Acute infection (D), Surgery (E), Certain medications (F), All of the above (G)</p> Signup and view all the answers

    Renal clearance refers to the rate at which the kidneys remove a substance from the plasma or blood.

    <p>True (A)</p> Signup and view all the answers

    What is the primary purpose of clearance tests in renal function assessment?

    <p>To determine the rate at which the kidneys remove substances from the plasma or blood</p> Signup and view all the answers

    Which of the following non-protein nitrogen (NPN) substances is present in the blood in the highest concentration?

    <p>Urea (A)</p> Signup and view all the answers

    Creatinine is produced primarily from the breakdown of muscle creatine.

    <p>True (A)</p> Signup and view all the answers

    What is the primary clinical condition associated with increased plasma levels of creatinine?

    <p>Renal insufficiency or kidney disease</p> Signup and view all the answers

    The ______ method is a common laboratory technique for measuring urea concentration in the blood.

    <p>Berthelot</p> Signup and view all the answers

    Match the following NPN substances with their primary clinical significance:

    <p>Urea = Renal function, fluid balance Creatinine = Renal function, muscle mass Uric acid = Gout, kidney stones</p> Signup and view all the answers

    Flashcards

    Renal System

    The system comprising two kidneys, ureters, bladder, and urethra.

    Nephrons

    The functional units of the kidneys, around 1 to 1.5 million per kidney.

    Renal Blood Flow

    The movement of blood through the kidneys, vital for renal function.

    Glomerulus

    A coil of capillary loops in the nephron where blood filtration occurs.

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    Bowman's Capsule

    A cup-like structure that encases the glomerulus and collects filtrate.

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    Tubular Reabsorption

    The process where the nephron reabsorbs water and essential substances from filtrate.

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    Tubular Secretion

    The process of transferring substances from blood into the tubular fluid.

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    Glomerular Filtration

    The initial process of filtering blood in the kidneys, affected by pressure differences.

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    Active Transport

    Reabsorption method requiring energy to move substances against a concentration gradient.

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    Renal Threshold

    The maximum concentration beyond which substances cannot be reabsorbed and are excreted.

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    Passive Transport

    Movement of substances without energy, from high to low concentration.

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    Blood Urea Nitrogen (BUN)

    A major nitrogenous waste product formed from protein catabolism in the body.

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    Glomerular Filtration Rate (GFR)

    Rate at which blood is filtered in the kidneys; directly related to BUN levels.

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    Exogenous vs Endogenous Proteins

    Exogenous: dietary proteins; Endogenous: proteins from cell breakdown.

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    BUN in dehydration

    In a dehydrated patient, 70% of BUN is reabsorbed and 30% is excreted, leading to increased serum BUN and decreased urine BUN.

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    Variables affecting BUN

    BUN is dependent on urea concentration, glomerular filtration rate (GFR), and level of hydration.

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    Azotemia

    An increase in blood urea and other nitrogenous compounds.

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    Prerenal azotemia causes

    Caused by decreased renal blood flow and conditions like dehydration, heart failure, and shock.

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    Renal azotemia conditions

    Includes acute kidney injury, glomerulonephritis, and nephrotic syndrome.

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    Postrenal azotemia causes

    Caused by obstruction such as tumors, prostatic hypertrophy, and nephrolithiasis.

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    BUN:Creatinine ratio

    Normal ratio is 12:1 to 20:1; both values are elevated proportionally in renal disease.

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    Uremia

    An increased urea level in the blood, often resulting from renal failure.

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    Hyperuricemia

    Elevated levels of uric acid in the blood, often leading to gout.

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    Primary Hyperuricemia

    Increased uric acid due to genetic factors or metabolic disorders, often causing gout.

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    Secondary Hyperuricemia

    Increased uric acid due to other medical conditions or external factors.

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    Gout

    A type of arthritis characterized by sudden, severe pain in joints due to uric acid crystals.

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    Uric Acid Measurement

    Methods to assess uric acid levels include phosphotungstic acid and uricase methods.

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    Renal Clearance

    The rate at which kidneys filter substances from the blood, expressed in mL/min.

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    Causes of Gout Attacks

    Factors such as alcohol, high-protein diets, and stress can precipitate gout attacks.

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    Uric Acid Symptoms

    Symptoms of high uric acid include joint pain, nephropathy, and kidney stones.

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    Prerenal Azotemia

    A condition characterized by high BUN ratios (>20:1 to 30:1) with normal CR, indicating decreased blood flow to kidneys.

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    Postrenal Obstruction

    Elevated BUN and CR ratios suggest this condition, indicating blockage after urine formation.

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    BUN Methodologies

    Different laboratory methods to measure Blood Urea Nitrogen levels in the body.

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    Urease Reaction

    A method where urea reacts with water to form ammonia, indicating kidney function.

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    Berthelot’s Reaction

    A method involving ammonium reaction with phenol and hypochlorite to create indophenol blue.

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    Nessler’s Reaction

    A colorimetric method that forms a yellow-brown compound when ammonium is added to a double iodide compound.

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    GLDH Procedure

    A common BUN measurement method that tracks NADPH decrease as ammonium reacts.

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    BUN Reference Range

    Normal BUN level is 7-18 mg/dL; high protein diets can raise BUN levels significantly.

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    Creatinine Clearance (CrCl)

    A test assessing kidney function using creatinine levels in serum and urine.

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    Formula for CrCl

    CrCl is calculated as U × V / P, where U is urine concentration, V is urine flow, P is plasma concentration.

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    Urine Concentration (U)

    The concentration of creatinine in urine, measured in mg/dL.

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    Plasma Concentration (P)

    The concentration of creatinine in blood plasma, measured in mg/dL.

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    Body Surface Area (BSA)

    A correction factor for calculating CrCl, standardly 1.73 m².

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    Dubois Formula

    Formula used to calculate body surface area: SA = W^0.425 × H^0.725 × 0.007184.

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    CrCl Reference Range (Males)

    Normal CrCl range for males is 97-137 mL/minute.

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    CrCl Reference Range (Females)

    Normal CrCl range for females is 88-128 mL/minute.

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    Non-Profit Nitrogen Substances

    Substances in blood that contain nitrogen but are not proteins, such as urea, creatinine, and uric acid.

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    Urea Biosynthesis

    A process in which ammonia, after being processed in the liver, is converted into urea for excretion.

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    Creatinine Levels

    Creatinine levels can indicate kidney function and muscle mass; increased levels suggest renal impairment.

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    Uric Acid Clinical Conditions

    Conditions like gout arise from elevated uric acid levels in blood, leading to joint pain.

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    Specimen Collection for Urea

    Blood samples for urea and creatinine should be handled carefully to avoid contamination and degradation.

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    Study Notes

    Nonprotein Nitrogen and Renal Function

    • Nonprotein nitrogen (NPN) compounds are byproducts of protein and nucleic acid catabolism. They contain nitrogen but are not part of a protein molecule.
    • Blood urea nitrogen (BUN) constitutes 45% of NPN compounds.
    • Amino acids account for 20% of NPN compounds.
    • Uric acid makes up 20% of these compounds.
    • Creatinine accounts for 5% of NPN compounds.
    • Creatine accounts for 1–2% of these compounds.
    • Ammonia accounts for 0.2% of NPN compounds.

    Introduction

    • Kidneys maintain the balance of substances within the human body.
    • This includes selectively retaining essential components and eliminating unnecessary ones.
    • Chemistry screening profiles measure renal function, water balance, and acid-base imbalances to diagnose renal disease.
    • The urinary system consists of two kidneys, two ureters, a bladder, and a urethra.

    Renal Anatomy

    • Kidneys consist of a cortex (outer layer) and a medulla (inner layer).
    • Each kidney contains approximately 1–1.5 million nephrons. These nephrons are the functional units of the kidney.
    • Renal blood flow is critical to kidney function, supplied by the renal artery.
    • Blood enters the nephron via the afferent arteriole.
    • Blood flows through the glomerulus.
    • Blood then flows through the efferent arteriole into the glomerulus. The filtrate from blood flows through the proximal convoluted tubule (PCT).
    • A glomerulus is a coil of approximately 40 capillary loops.
    • These loops are located within Bowman's capsule.
    • The filtrate passes through the loops and into the proximal convoluted tubule (PCT).

    Box 11-1 Urinary Filtrate Flow

    • The flow of filtrate through the nephron is as follows: Bowman's capsule, PCT, descending loop of Henle, ascending loop of Henle, DCT, collecting duct, renal calyces, ureter, bladder, urethra.

    Box 11-2 Renal Blood Flow

    • Renal blood flow follows a sequence: renal artery, afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries, vasa recta, renal vein.

    Renal Physiology

    • The three main renal functions are glomerular filtration, tubular reabsorption, and tubular secretion.
    • Glomerular Filtration: Enhanced by high pressure in glomerular capillaries due to the difference in afferent and efferent arteriole size. The glomerular basement membrane repels large, negatively charged molecules like proteins.
    • Tubular Reabsorption: Active transport requires a carrier protein and energy (ATP) to move substances from the tubular fluid to the bloodstream. Substances are reabsorbed based on the renal threshold (concentration that can be reabsorbed). Passive transport requires no energy and moves substances based on concentration gradients - water and urea are reabsorbed using this transport.
    • Tubular Secretion: Substances move from the peritubular capillaries into the filtrate. The kidneys eliminate certain wastes and regulate acid-base balance by secreting hydrogen ions.

    Analytes Associated with Renal Function

    • NPN compounds (BUN, amino acids, uric acid, creatinine, creatine, ammonia) are products of protein and nucleic acid metabolism, not part of the protein molecule.
    • Urea (BUN) is a major nitrogen-containing metabolic product of protein catabolism in humans. BUN forms from exogenous and endogenous proteins.
    • A direct relationship exists between urea and glomerular filtration rate (GFR). In healthy individuals, approximately 40% of BUN is reabsorbed, and 60% is excreted. Azotemia (elevated BUN) is classified as prerenal, renal, or postrenal based on the cause. Azotemia can result in Azotemia (elevated blood urea and other NPN compounds), increasing to Uremia.

    Analytes Associated with Renal Function Methodologies

    • Urease: Urea reacts with 2H₂O to form 2NH₄⁺ + CO₃²⁻ (Berthelot's reaction): Ammonia reacts with phenol and hypochlorite to produce indophenol blue, which can be measured.
    • Nessler's: The addition of a double iodide compound results in a colored compound with NH₄⁺, which can be measured.
    • Glutamate Dehydrogenase (GLDH): Measuring the disappearance of NADPH (and the increase of NAD+) as it is oxidized, provides a quantitative method for ammonia.
    • Diacetyl or Fearon Reaction: Colorimetric, a condensation of diacetyl with urea produces diazine, which can measured in urine.

    Creatinine

    • Synthesized in the liver from three amino acids (arginine, glycine, methionine).
    • Creatinine is derived from creatine phosphate.
    • Creatinine levels are proportional to muscle mass.
    • Creatinine is freely filtered by the glomeruli and is not significantly reabsorbed, making it an excellent marker of GFR. Creatinine levels are affected by muscle mass, creatine turnover, and renal function. The Jaffe and enzymatic methods are used to detect creatinine.
    • Clinical significance of Creatinine: The amount present in the blood can be used to measure GFR. A high concentration in serum indicates a problem with glomerular filtration.

    Uric Acid

    • Uric acid is a major product of purine metabolism.
    • Uric acid is produced in the liver from xanthine.
    • Uric acid forms from dietary and endogenous nucleotides and cellular breakdown.
    • Hyperuricemia (serum UA >7.0 mg/dL) is caused by increased dietary intake, overproduction, or underexcretion of uric acid. Clinical significance of uric acid includes several categories of hyperuricemia: primary and secondary cause. These causes can lead to gout and other issues (e.g., nephrolithiasis).
    • Methods to measure uric acid include Phosphotungstic acid (a blue color develops) and Uricase (measuring allantoin).

    Analytical Procedures for Assessment of Glomerular Filtration

    • Renal Clearance: The rate the kidneys remove a substance from plasma or blood, expressed in mL cleared/minute. Creatinine is a good indicator, freely filtered, not reabsorbed, and constantly released.
    • Creatinine Clearance (CrCl): Calculated using serum and urine creatinine levels and urine volume. CrCl is corrected to an adult body surface area (BSA) of 1.73 m² using Dubois formula. Especially important for small or pediatric patients and obese patients.
    • eGFR: Methods to estimate GFR used from a serum creatinine level. The MDRD equation is effective for those 18 years of age and older.
    • Protein:Creatinine Ratio: Normal is <100–150 mg/24h.
    • Inulin Clearance: An endogenous polysaccharide, the inulin level in serum and urine is measured over three hours.
    • Cystatin C: A low-molecular-weight protein produced by nucleated cells at a constant rate. It's freely filtered, not reabsorbed, and not affected by muscle mass, diet, or age; it's an appropriate measurement of GFR.

    Screening for Renal Disease

    • Serum Protein: Severe renal disease decreases serum proteins and albumin.
    • β-Microglobulin (BMG): Increased levels are in renal failure and can be used to evaluate renal tubular function.
    • Low-Molecular-Weight Proteins: Include α₁-microglobulin, α₂-microglobulin, β-trace protein, and cystatin C.
    • Urinalysis: Routine urinalysis helps diagnose renal issues (proteinuria, presence of red blood cells or leukocytes, albumin). Proteinuria and microalbumin are often early signs of impaired renal function.

    Renal Pathophysiology

    • Glomerular Disease: Primarily damage to the glomeruli of the renal nephron.
    • Glomerulonephritis (Acute/Chronic): Acute inflammation of the glomeruli (often post-streptococcal infection) that may progress to scarring and renal failure, characterized by rapid onset, fever, malaise, nausea, oliguria, hematuria, and proteinuria.
    • Nephrotic Syndrome: Complications from glomerulonephritis and other conditions, Characterized by edema, fatigue, hypertension, anemia, metabolic acidosis, proteinuria, and potentially decreased urine volume.
    • Pyelonephritis: Inflammatory process involving bacterial infection of the renal tubules, usually caused by ascending infection. May be chronic, leading to permanent scarring.
    • Cystitis: Bladder infection characterized by dysuria, more common in females, can lead to pyelonephritis.
    • Chronic Kidney Disease (CKD): Gradual loss of kidney function, related to diabetes (the main cause), hypertension, autoimmune diseases, urinary issues, and some medications.
    • Renal Failure: Acute, marked increase in serum creatinine and a significant decline in GFR. Results from causes like acute tubular necrosis. Symptoms include decreased urine production (oliguria, anuria).
    • Renal Calculi: Solid aggregates of chemical or mineral salts formed in the renal tubules. More common in males. Risk factors include dehydration, diet, urinary pH, and urinary stasis. Symptoms include severe pain, nausea, vomiting.

    Dialysis

    • Treatment option for renal failure or end-stage renal disease (ESRD).
    • Dialysis separates large macromolecules from low-molecular-weight compounds using a semipermeable membrane, including hemodialysis (HD) and peritoneal dialysis (PD).
    • Dialysis patients need frequent evaluation for well-being, cardiovascular risk, malnutrition risk, and degree of achievable ultrafiltration.
    • Complications like anemia, cardiovascular disease, and malnutrition can occur in people on dialysis.

    Postamble

    • Students must review the textbook to fully grasp the unit objectives and answer test questions. The PowerPoint is a summary—not the full material.

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    Test your knowledge on renal tubular reabsorption, tubular secretion, and the structures of the urinary system. This quiz covers key concepts related to kidney functions and the nephron's anatomy. Perfect for students studying human physiology and anatomy.

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