patho2 test 2 Glomerular & Tubular Disorders ppt
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Questions and Answers

What is the primary effect of glomerular disease on the kidney's filtering function?

  • Increased glomerular filtration rate
  • Changes in glomerular capillary permeability
  • Altered glomerular blood pressure
  • Decreased glomerular filtration rate (correct)

    • What is the primary cause of Nephritic Syndrome?

  • Immune complex deposition leading to damage to the mesangium
  • Antigen deposition leading to damage to the endothelial cells (correct)
  • Inflammation of the glomerular capillaries
  • Antibody deposition leading to damage to the podocytes

    • Which of the following signs is NOT associated with Nephritic Syndrome?

  • Oliguria
  • Hematuria
  • Hypocalcemia (correct)
  • Proteinuria

    • What is the primary reason for the development of hypertension in glomerular disease?

    <p>Retention of sodium and water due to decreased GFR</p> Signup and view all the answers

    What is the primary difference between Nephrotic and Nephritic Syndromes?

    <p>Type of damage</p> Signup and view all the answers

    Which of the following conditions is associated with Nephritic Syndrome?

    <p>Infection-related Glomerulonephritis</p> Signup and view all the answers

    What is the likely response of the Juxtaglomerular Apparatus to low GFR?

    <p>Increase renin to increase systemic blood pressure</p> Signup and view all the answers

    What is the primary cause of secondary nephrotic syndrome?

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

    What is the characteristic feature of the glomerular capillary wall in glomerulonephritis?

    <p>Thickening of the capillary wall</p> Signup and view all the answers

    What is the typical outcome of acute glomerulonephritis?

    <p>Recovery of all renal function</p> Signup and view all the answers

    What is the primary mechanism of post-streptococcal glomerulonephritis?

    <p>Immune complex deposition</p> Signup and view all the answers

    What is the characteristic feature of minimal change glomerulonephritis?

    <p>No visible changes on light microscopy</p> Signup and view all the answers

    What is the primary cause of lipiduria in nephrotic syndrome?

    <p>Increased lipoprotein synthesis</p> Signup and view all the answers

    What is the primary mechanism of proteinuria in nephrotic syndrome?

    <p>Increased glomerular permeability</p> Signup and view all the answers

    What is the characteristic feature of nephrotic syndrome?

    <p>Proteinuria and hypoalbuminemia</p> Signup and view all the answers

    What is the primary cause of glomerulonephritis?

    <p>All of the above</p> Signup and view all the answers

    Which of the following are characteristics of Type I Rapidly Progressive Glomerulonephritis (RPGN)?

    <p>Anti-glomerular basement membrane (anti-GBM) antibodies, linear fashion</p> Signup and view all the answers

    What is the most common cause of nephrotic syndrome in children?

    <p>Minimal Change Glomerulonephritis</p> Signup and view all the answers

    Which type of Rapidly Progressive Glomerulonephritis (RPGN) is caused by antibodies to neutrophil cytoplasm?

    <p>Type III</p> Signup and view all the answers

    What is the name of the disease that is characterized by both alveolar and glomerular involvement due to the presence of anti-GBM antibodies?

    <p>Goodpasture's</p> Signup and view all the answers

    Which of the following is a characteristic of Membranous Glomerulonephritis?

    <p>Complement-mediated membrane attack complex, leaky glomeruli</p> Signup and view all the answers

    What is the most common cause of chronic renal failure?

    <p>Secondary Glomerulonephritis</p> Signup and view all the answers

    Which type of Glomerulonephritis is characterized by a sudden appearance of proteinuria and edema?

    <p>Minimal Change Glomerulonephritis</p> Signup and view all the answers

    What is the name of the disease that is characterized by the presence of anti-neutrophil cytoplasm antibodies and is a type of Type III RPGN?

    <p>Granulomatosis with polyangiitis (GPA)</p> Signup and view all the answers

    What is the name of the disease that is characterized by the deposition of immune complexes in a granular pattern?

    <p>Type II RPGN</p> Signup and view all the answers

    Which of the following is a characteristic of Chronic Glomerulonephritis?

    <p>Slow progression, often asymptomatic</p> Signup and view all the answers

    What is the primary function of the kidney in maintaining homeostasis?

    <p>Regulation of body fluid volume and osmolality</p> Signup and view all the answers

    What is the function of the renal medulla?

    <p>Formation of renal pyramids</p> Signup and view all the answers

    What is the function of erythropoietin produced by the kidney?

    <p>Stimulation of red blood cell production</p> Signup and view all the answers

    What is the location of the kidney in the human body?

    <p>Retroperitoneal region alongside the vertebral column</p> Signup and view all the answers

    What is the function of the renal cortex?

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

    What is the function of the hilum of the kidney?

    <p>Entry and exit point of renal artery and vein</p> Signup and view all the answers

    What percentage of cardiac output is received by the kidneys?

    <p>25%</p> Signup and view all the answers

    What is the route of blood flow from the peritubular capillaries?

    <p>Peritubular capillaries &gt; interlobular vein &gt; renal vein &gt; IVC</p> Signup and view all the answers

    What is the function of the glomerular capillaries?

    <p>Filter waste and excess substances from the blood</p> Signup and view all the answers

    What is unique about each kidney's ability to regulate blood flow?

    <p>Each kidney can auto-regulate flow through each capillary bed</p> Signup and view all the answers

    What is a characteristic of nephrons in the kidney?

    <p>The kidney is unable to regenerate lost nephrons</p> Signup and view all the answers

    What is the primary function of the juxtamedullary nephrons?

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

    What determines the amount of substance excreted in the urine?

    <p>Amount filtered + amount secreted - amount reabsorbed</p> Signup and view all the answers

    What is the function of the visceral epithelium in the glomerulus?

    <p>To allow filtration through filtration slits</p> Signup and view all the answers

    What is the name of the space where filtration occurs in the glomerulus?

    <p>Urinary space</p> Signup and view all the answers

    What is unique about the glomerular capillaries?

    <p>They are the only capillaries fed and drained by arterioles</p> Signup and view all the answers

    What is the function of the juxtaglomerular apparatus?

    <p>To regulate renal blood flow</p> Signup and view all the answers

    What is the characteristic feature of the glomerular filtration barrier?

    <p>It has a charge barrier for negatively charged proteins</p> Signup and view all the answers

    What is the primary function of the peritubular capillaries?

    <p>To reabsorb filtrate</p> Signup and view all the answers

    What is the main driving force for filtration in the kidney?

    <p>Mechanical energy from systole</p> Signup and view all the answers

    What is the primary difference between cortical and juxtamedullary nephrons?

    <p>Length of the loop of Henle</p> Signup and view all the answers

    What type of pressure helps prevent excessive fluid filtration in the nephron?

    <p>Oncotic pressure</p> Signup and view all the answers

    What is the name of the structure where the distal tubule passes between the afferent and efferent arterioles?

    <p>Juxtaglomerular apparatus</p> Signup and view all the answers

    What is the normal rate of glomerular filtration?

    <p>125 mL/min</p> Signup and view all the answers

    What is the primary factor that determines the glomerular filtration rate?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of autoregulation of renal blood flow?

    <p>To maintain a constant renal blood flow</p> Signup and view all the answers

    What is the result of decreased albumin synthesis in cirrhosis?

    <p>Hypoalbuminemia and edema</p> Signup and view all the answers

    What is the effect of increased hydrostatic pressure on the glomerulus?

    <p>Increased glomerular filtration rate</p> Signup and view all the answers

    What is the primary mechanism of myogenic autoregulation in the kidney?

    <p>Vasoconstriction of afferent arterioles</p> Signup and view all the answers

    What is the purpose of the glomerular filtration rate?

    <p>To regulate the composition and volume of body fluids</p> Signup and view all the answers

    What is the primary determinant of glomerular filtration rate?

    <p>All of the above</p> Signup and view all the answers

    What is the primary mechanism by which the kidneys eliminate highly protein-bound substances?

    <p>Tubular secretion</p> Signup and view all the answers

    Which of the following is an example of a prerenal cause of kidney injury?

    <p>Renal artery stenosis</p> Signup and view all the answers

    What is the primary consequence of bilateral ureteral obstruction?

    <p>Renal failure</p> Signup and view all the answers

    What is the characteristic of chronic kidney disease?

    <p>Slow, progressive loss of renal function</p> Signup and view all the answers

    Which of the following is a common example of a postrenal cause of kidney injury?

    <p>Benign prostatic hyperplasia</p> Signup and view all the answers

    What is the primary mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) decrease renal blood flow?

    <p>Blockage of prostaglandins synthesis</p> Signup and view all the answers

    What is the primary difference between acute kidney injury and chronic kidney disease?

    <p>Duration of the damage</p> Signup and view all the answers

    What is the primary consequence of end-stage renal disease (ESRD)?

    <p>Dialysis is needed</p> Signup and view all the answers

    What is the primary mechanism of hypertensive nephropathy?

    <p>Microvascular damage from constant exposure to high systemic blood pressure</p> Signup and view all the answers

    What is the effect of uncontrolled diabetes on the kidneys?

    <p>Microvascular damage leading to 'leaky' basement membrane and proteinuria</p> Signup and view all the answers

    What percentage of normal renal function is typically left when dialysis is needed?

    <p>&lt; 10%</p> Signup and view all the answers

    What is the primary function of the peritoneal membrane in peritoneal dialysis?

    <p>To act as a semi-permeable membrane for fluid filtration</p> Signup and view all the answers

    What is the genetic inheritance pattern of Autosomal Recessive Polycystic Kidney Disease?

    <p>Autosomal recessive</p> Signup and view all the answers

    What is the typical age of presentation of Autosomal Dominant Polycystic Kidney Disease?

    <p>30-60 years</p> Signup and view all the answers

    What is the effect of chronic kidney disease on the kidney's mechanisms for maintaining systemic blood pressure?

    <p>It impairs the kidney's ability to regulate blood pressure, leading to a vicious cycle</p> Signup and view all the answers

    What is the effect of high systemic blood pressure on the kidney's afferent arterioles?

    <p>It causes chronic constriction of the afferent arterioles</p> Signup and view all the answers

    What is the primary mechanism of progressive decline in GFR in hypertensive nephropathy?

    <p>Microvascular damage leading to tissue fibrosis and ischemia</p> Signup and view all the answers

    What is the typical outcome of Autosomal Recessive Polycystic Kidney Disease?

    <p>End-stage renal failure by age 15</p> Signup and view all the answers

    What happens to the renal blood flow and GFR when the juxtaglomerular apparatus senses a decrease in fluid/solute in the distal tubule?

    <p>Vasodilation of the afferent arteriole and increase in GFR</p> Signup and view all the answers

    How can the kidney increase GFR?

    <p>Dilate the afferent arteriole and constrict the efferent arteriole</p> Signup and view all the answers

    What is the purpose of measuring creatinine levels in the plasma and urine?

    <p>To estimate the glomerular filtration rate</p> Signup and view all the answers

    What happens to substances that are freely filtered in the glomerulus but not reabsorbed in the tubules?

    <p>They are excreted in the urine</p> Signup and view all the answers

    What is the purpose of the transport maximum in tubular reabsorption?

    <p>To regulate the amount of solutes reabsorbed into the bloodstream</p> Signup and view all the answers

    What is the significance of the proximal tubule in the nephron?

    <p>It is the site of tubular reabsorption and secretion</p> Signup and view all the answers

    What happens to the GFR when the efferent arteriole is constricted?

    <p>GFR increases due to increased hydrostatic pressure</p> Signup and view all the answers

    What is the role of the macula densa in the juxtaglomerular apparatus?

    <p>It senses changes in fluid/solute in the distal tubule and regulates GFR</p> Signup and view all the answers

    What is the significance of the glomerular capillaries in the nephron?

    <p>They are the site of glomerular filtration</p> Signup and view all the answers

    What is the role of the collecting duct in the nephron?

    <p>It is the site of urine formation and concentration</p> Signup and view all the answers

    What is the primary function of the proximal tubule in the nephron?

    <p>To reabsorb most of the sodium and water from the filtrate</p> Signup and view all the answers

    What is the function of the loop of Henle in the nephron?

    <p>To concentrate the urine through the countercurrent mechanism</p> Signup and view all the answers

    What is the primary difference between the apical and basolateral surfaces of tubular epithelial cells?

    <p>The apical surface faces the tubule, while the basolateral surface faces the interstitium and peritubular capillary</p> Signup and view all the answers

    What is the primary mechanism of urine concentration in the nephron?

    <p>Countercurrent multiplication mechanism</p> Signup and view all the answers

    What is the primary function of the peritubular capillaries in the nephron?

    <p>To supply the tubular epithelial cells with oxygen and nutrients</p> Signup and view all the answers

    What is the primary function of the juxtaglomerular apparatus in the nephron?

    <p>To regulate blood pressure through the renin-angiotensin-aldosterone system</p> Signup and view all the answers

    What is the primary mechanism of sodium reabsorption in the proximal tubule?

    <p>Coupled with glucose, amino acids, lactate, and phosphate reabsorption</p> Signup and view all the answers

    What is the primary function of the glomerular capillaries in the nephron?

    <p>To filter the blood and form the filtrate</p> Signup and view all the answers

    What is the primary function of the ascending limb of the loop of Henle?

    <p>Reabsorption of sodium</p> Signup and view all the answers

    What is the effect of loop diuretics on the kidney?

    <p>Inhibits the normal sodium/potassium transporter in the ascending limb of the loop of Henle</p> Signup and view all the answers

    What is the primary function of aldosterone in the distal tubule?

    <p>Regulation of sodium levels</p> Signup and view all the answers

    What is the effect of anti-diuretic hormone (ADH) on the collecting duct?

    <p>Increases water permeability</p> Signup and view all the answers

    What is the primary mechanism of thiazide diuretics?

    <p>Inhibition of the Na+/Cl- cotransporter</p> Signup and view all the answers

    What is the effect of potassium-sparing diuretics on potassium levels?

    <p>Increases potassium levels</p> Signup and view all the answers

    What is the characteristic feature of obstructive uropathies?

    <p>Complete or partial blockage of the urinary system</p> Signup and view all the answers

    What is the primary effect of collecting system dilation in obstructive uropathy?

    <p>Compression of surrounding renal parenchyma</p> Signup and view all the answers

    What is the primary mechanism of sodium reabsorption in the distal tubule?

    <p>Aldosterone-dependent</p> Signup and view all the answers

    What is the primary function of the renal medulla?

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

    What is the primary mechanism of fibrosis in the tubules and interstitial space?

    <p>Overabundance of cytokines causing cell damage</p> Signup and view all the answers

    What is the typical timeline for cell death to occur in obstructive uropathy?

    <p>More than 4 weeks</p> Signup and view all the answers

    What is the primary cause of Acute Tubular Necrosis (ATN)?

    <p>Ischemia and nephrotoxicity</p> Signup and view all the answers

    What is the effect of ischemia on tubular cells?

    <p>Decreased production of vasodilators</p> Signup and view all the answers

    What is the characteristic feature of urine in ischemic ATN?

    <p>Muddy appearance</p> Signup and view all the answers

    What is the primary indication for hemodialysis in the acute setting?

    <p>Volume overload</p> Signup and view all the answers

    What is the characteristic feature of the recovery phase of ATN?

    <p>Gradual decrease in BUN and creatinine levels</p> Signup and view all the answers

    What is the primary reason why ATN is a significant concern in clinical practice?

    <p>Association with a more than fourfold increased likelihood of death</p> Signup and view all the answers

    What is the primary difference between the initiation and maintenance phases of ATN?

    <p>GFR is lower in the initiation phase</p> Signup and view all the answers

    What is the primary mechanism of post-ATN diuresis?

    <p>Increased urine output due to regenerating tubular cells</p> Signup and view all the answers

    Study Notes

    Glomerular Diseases

    • Impairment of the filtering properties of the glomerulus leads to decreased GFR
    • Can be primary or secondary
    • Molecules that normally aren't filtered (like blood cells, Albumin) can pass into the urine and be excreted

    Nephrotic and Nephritic Syndromes

    • Syndrome: specific constellation of signs or symptoms that can be due to one cause or may have many causes
    • Which syndrome a patient with glomerular damage manifests depends on the amount of damage, type of damage, and severity

    Nephritic Syndrome

    • Inflammatory cells accumulate in the mesangium (support cells surrounding the glomerular capillaries)
    • Caused by antigen deposition leading to damage to the endothelial cells
    • Damage thins the glomerular basement membrane and podocytes making "holes" big enough to permit proteins and red cells through into the filtrate
    • Signs: Hematuria, Hypertension, Oliguria, Edema
    • Associated with: Infection-related Glomerulonephritis, Rapidly Progressive Glomerulonephritis (RPGN)

    Nephrotic Syndrome

    • Damage to the glomerular basement membrane/podocytes leads to loss of the negative charge = increased permeability
    • Plasma proteins are lost (excreted) decreasing plasma oncotic pressure
    • Can be primary or secondary
    • Diabetes is the most common cause of secondary, HTN is the second most common
    • Signs:
      • Proteinuria (> 3.5 gm/day)
      • Hypoalbuminemia (low serum protein)
      • Ascites and peripheral edema
      • Hyperlipidemia
      • Lipiduria (lipids in urine)
    • Associated with: Minimal Change Nephropathy, Membranoproliferative Glomerulonephritis, IgA Nephropathy (Berger Disease)

    Glomerulonephritis

    • Definition: inflammation (-itis) of the glomeruli
    • Group of autoimmune disorders that involve inflammation of the glomerular capillaries
    • Present with some combination of the findings we have already discussed:
      • Hematuria
      • Proteinuria
      • Oliguria/decreased GFR
      • Hypertension
    • Most are autoimmune and named for etiology, microscopic findings and/or clinical syndrome

    Types of Glomerulonephritis

    • Acute Glomerulonephritis
    • Post-Streptococcal Glomerulonephritis
    • Rapidly Progressive Glomerulonephritis
    • Membranous Glomerulonephritis
    • Minimal Change Glomerulonephritis
    • Chronic Glomerulonephritis
    • Secondary Glomerulonephritis

    Acute Glomerulonephritis

    • Primary glomerular injury from immunologic responses, ischemia, drugs, toxins, infection
    • Secondary glomerular injury: DM, heart failure, lupus, HIV
    • Characterized by abrupt onset of hematuria/proteinuria with decreased GFR and sodium/fluid retention
    • ACUTE means typically followed by recovery of all renal function
    • Causes:
      • Poststreptococcal glomerulonephritis
      • Multisystem diseases: systemic lupus, vasculitis, Goodpasture's syndrome
      • Primary glomerular disease: IgA nephropathy, mesangial proliferative glomerulonephritis
      • Miscellaneous: Guillain-Barre syndrome

    Post-Streptococcal Glomerulonephritis

    • In some people, when the immune system creates antibodies to Group A strep, those antibodies are cross-reactive to a "self" antigen within the glomerulus
    • Immune system complexes and complement then collect within glomerular capillaries and the mesangial spaces
    • Inflammatory cells can collect there as well– as a response to the antibody collections
    • Symptoms usually occur about 7-10 days after the original infection– that's when the original infection has been handled, but circulating antibodies are still present
    • Symptoms usually resolve several weeks after their onset

    Rapidly Progressive Glomerulonephritis (RPGN)

    • Can be secondary to post-strep GN or due to "unknown causes"
    • Always autoimmune
    • Deposition of antibody/antigen complexes
    • Another name is "crescentic" GN due to proliferation of epithelial cells in Bowman's space
    • Usually, GFR drops by 50% within 3 months and if left untreated will progress to renal failure
    • Generally, presents as a NEPHRITIC syndrome

    Classifications of RPGN

    • Type I (25%): most common example is Goodpasture's
    • Type II (25%): Lupus, IgA nephropathy, post-strep GN
    • Type III (50%): most common example = Granulomatosis with polyangiitis (GPA)

    The Renal System

    • The renal system's main organ, the kidney, maintains homeostasis, regulates body fluid composition and excretion of waste and foreign substances, controls body fluid volume and osmolality, regulates acid-base balance, and has hormonal and metabolic functions.

    Gross Anatomy of the Kidney

    • The kidney is a retroperitoneal organ located alongside the vertebral column at T12-L3.
    • The outer region is the cortex, and the inner region is the medulla.
    • The hilum is where the renal artery and nerves enter and the renal vein exits.
    • The ureter exits to drain urine from the kidneys to the bladder.

    Renal Perfusion

    • The kidney is one of the most well-perfused organs in the body, receiving about 25% of cardiac output.
    • The right and left renal arteries branch off from the abdominal aorta and enter through the hilum.

    Renal Capillaries

    • There are two capillary beds: glomerular and peritubular.
    • Glomerular capillaries filter, and peritubular capillaries reabsorb fluid and solutes back into circulation.

    The Nephron

    • The nephron is the functional unit of the kidney, with about 1 million per kidney.
    • The kidney cannot regenerate nephrons, so lost nephrons are compensated by remaining nephrons.
    • The nephron consists of the glomerulus, Bowman's capsule, proximal tubule, Loop of Henle, distal tubule, and collecting duct.

    Nephron Types

    • Cortical nephrons have glomeruli in the outer region of the cortex and short loops of Henle that dip into the medulla.
    • Juxtamedullary nephrons have glomeruli in the cortex near the medulla, with long loops of Henle that travel deep into the medulla.

    Functions of the Nephron

    • Three processes determine the amount of substance excreted in the urine: glomerular filtration, tubular reabsorption, and tubular secretion.

    Glomerular Filtration

    • Glomerular filtration is a passive process using hydrostatic and oncotic pressures to force fluids and solutes through a membrane.
    • The driving force for filtration is the mechanical energy from systole creating a pressure wave in the afferent and efferent arterioles.

    Tubular Reabsorption and Secretion

    • Tubular reabsorption is the movement of fluid and solutes from the tubule lumen back into the peritubular capillaries.
    • Tubular secretion is the movement of fluid and solutes from the peritubular capillaries into the tubular lumen.

    Glomerular Filtration Rate (GFR)

    • GFR is the volume of plasma filtered in the glomeruli per unit time, with a normal rate of 125 mL/min or 180 L/day.
    • GFR is influenced by age, gender, ideal body weight, body surface area, and the number of functional nephrons.

    Determinants of GFR

    • Amount of filtration surface area available
    • Filtration membrane permeability and net filtration pressure
    • Systemic blood pressure and blood flow to the glomerular capillaries

    Autoregulation of Renal Blood Flow

    • The kidney can maintain a constant renal blood flow and GFR despite changes in systemic blood pressure through two mechanisms: myogenic autoregulation and feedback from the juxtaglomerular apparatus.

    Regulation of RBF and GFR

    • The kidney can decrease GFR by constricting the afferent arteriole or dilating the efferent arteriole.
    • The kidney can increase GFR by dilating the afferent arteriole or constricting the efferent arteriole.

    Clinical Correlation: GFR

    • GFR can be measured by choosing a substance that is freely filtered in the glomerulus but not reabsorbed in the tubules, such as creatinine.

    Tubular Pathway Review

    • Transport (reabsorption and secretion) takes place in every part of the tubule.
    • The tubular pathway consists of the proximal tubule, Loop of Henle, and collecting duct.

    Pathophysiology of the Kidney

    • Each function of the renal system can be compromised, resulting in various pathologies depending on the location, duration, and etiology of the damage.

    Classifying Renal Disease

    • Renal diseases can be classified by chronicity (acute or chronic), location (prerenal, intrarenal, or postrenal), and etiology.

    Glomerulotubular Diseases

    • Glomerulotubular diseases will be covered in a later lecture.

    Causes of Kidney Injury: Location

    • Prerenal causes include inadequate renal blood flow, leading to decreased GFR.
    • Intrarenal causes include nephron damage and glomerulotubular diseases.
    • Postrenal causes include obstruction or structural defects blocking urine from draining.

    Chronic Kidney Disease

    • Chronic kidney disease is a slow, progressive loss of renal function and decrease in GFR.
    • Causes include systemic diseases, intrinsic kidney disease, and obstructive uropathies.
    • Defined in stages based on GFR and dialysis dependence.

    Hypertensive Nephropathy

    • Hypertensive nephropathy is a result of chronic high systemic blood pressure, leading to microvascular damage, tissue fibrosis, and eventually renal failure.

    Diabetic Nephropathy and CKD

    • Diabetic nephropathy is a complication of uncontrolled diabetes, causing microvascular damage to renal arteries and direct glomerular damage, leading to proteinuria and decreased GFR.

    CKD and Renal Adaptation

    • The kidney's autoregulation and adaptation mechanisms allow for preservation of renal function over time despite chronic insults.
    • Eventually, enough damage occurs, and the kidneys can no longer compensate, leading to symptomatic or clinically significant changes in renal function.

    Clinical Correlation: Dialysis

    • In both AKI and CKD, dialysis may be necessary to filter blood and remove volume.
    • Hemodialysis uses an external glomerular membrane and tubule system to filter undesired substances, remove volume, and maintain a normal balance of solutes.
    • Peritoneal dialysis uses the peritoneal membrane to filter plasma and water, with a high-osmotic concentration dialysate instilled into the abdomen.

    Tubular Epithelial Cells

    • Connected with tight junctions, with two different surfaces: apical-luminal side (faces into the tubule) and basolateral side (faces the interstitium and tubular capillary)
    • This allows for reabsorption from the tubule into the bloodstream and secretion from the bloodstream into the tubules

    Proximal Tubule - "Every"

    • Reabsorbs nearly every substance that gets filtered in the glomerulus
    • 2/3 of sodium and water reabsorption happens here
    • Water reabsorption is not ADH dependent
    • Located in the cortex along with the glomeruli
    • Filtrate flows directly into the proximal tubule from the glomerulus

    Reabsorption in Proximal Tubule

    • Glomerular filtration: hydrostatic pressure drives fluid out into Bowman's capsule
    • Fluid is protein-free, increasing plasma oncotic pressure, which decreases hydrostatic pressure and ultimately stops filtration
    • Plasma with increased oncotic pressure heads into the efferent arteriole, then to the peritubular capillary, causing fluid to move from the tubule into the peritubular capillaries
    • Na reabsorption is coupled with the reabsorption of glucose, amino acids, lactate, and phosphate

    Loop of Henle

    • Responsible for urine concentration
    • Uses a countercurrent mechanism to concentrate urine
    • Proximal tubule reabsorbs water and NaCl simultaneously, but the loop of Henle splits the reabsorption of water and NaCl

    Urine Concentration

    • Countercurrent multiplying mechanism: fluid in one tube flows the opposite way of fluid in the adjoining tube
    • Proximal tubule reabsorbs water and NaCl simultaneously, then the loop of Henle splits the reabsorption of water and NaCl

    Descending Limb - "Waterfall"

    • Descending limb is impermeable to solutes but freely permeable to water
    • More water is absorbed the deeper down in the medulla we go

    Ascending Limb - "Raises Sodium"

    • Ascending limb is freely permeable to solutes (sodium) but not to water
    • Sodium is reabsorbed, and water stays in the tubule

    Distal Tubule - "In Exchange for Potassium"

    • Regulation of sodium and potassium levels happens here through sodium reabsorption and potassium secretion
    • Acid-base regulation through H+ secretion and bicarbonate reabsorption also happens here

    Collecting Duct - "To Make Another Waterfall"

    • Last part of the renal tubule, delivers filtrate to the renal pelvis/ureters to head to the bladder for excretion
    • Most like the descending loop of Henle - water is reabsorbed here (another place of only fine-tuning)
    • Here, water reabsorption is dependent on anti-diuretic hormone (ADH, vasopressin)

    Renin-Angiotensin-Aldosterone Axis

    • Key controller = aldosterone
    • Steroid from the adrenal cortex
    • Increases Na+ reabsorption in both the distal tubule and collecting ducts

    Obstructive Uropathies

    • Complete or partial blockage of the urinary system
    • Leads to "backup" of urine flow, which eventually backs up into the collecting system
    • Collecting system dilates, compressing surrounding renal parenchyma, causing ischemia and damage

    Causes of Obstructive Uropathies

    • Severity of the obstruction depends on factors such as unilateral or bilateral, partial vs. complete obstruction, cause of the obstruction, and duration

    Path of Damage in Obstructive Uropathy

    • Collecting system dilates, triggering growth of new tissue in the ureters (smooth muscle hypertrophy)
    • Flow slows down tremendously or even stops, decreasing GFR
    • Collecting system stretches and enlarges, damaging tubular cells
    • Fibrosis begins in the tubules and interstitial space, calling in cytokines
    • Overabundance of cytokines brings in proteases, causing more cell damage and eventually apoptosis of injured cells

    Clinical Correlation: Loop Diuretics

    • "Loop" diuretics like Furosemide and Bumetanide work by inhibiting the normal sodium/potassium transporter in the ascending limb of the loop of Henle
    • Keeping more sodium in the tubule keeps more water in the tubule, leading to diuresis

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    Description

    This quiz covers the causes and effects of glomerular diseases, including impairment of filtering properties, decreased GFR, and nephrotic and nephritic syndromes. Learn how glomerular damage affects the kidneys and urine.

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