Human Kidney Function and Regulation
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Questions and Answers

What is one of the substances the kidneys excrete to prevent toxicity?

  • Lactate
  • Penicillin (correct)
  • Glucose
  • Urea

Which ion do the kidneys excrete when the extracellular fluid is acidic?

  • Calcium ions (Ca²⁺)
  • Potassium ions (K⁺)
  • Sodium ions (Na⁺)
  • Hydrogen ions (H⁺) (correct)

What hormone produced by the kidneys stimulates red blood cell production?

  • Calcitriol
  • Insulin
  • Renin
  • Erythropoietin (correct)

Where are the kidneys located in the human body?

<p>In the posterior abdominal wall (A)</p> Signup and view all the answers

What is the primary function of the nephron's vascular component?

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

Which of the following structures merge into the efferent arterioles?

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

What role do peritubular capillaries play in kidney function?

<p>They provide nourishment to renal tissues (D)</p> Signup and view all the answers

What is the normal arterial blood pH maintained by the kidneys?

<p>7.4 (A)</p> Signup and view all the answers

What is the primary role of the kidneys in maintaining blood pressure?

<p>Altering the excretion of sodium in urine (C)</p> Signup and view all the answers

Which substance is NOT a metabolic waste product removed by the kidneys?

<p>Glucose (C)</p> Signup and view all the answers

Which hormone is produced by the kidneys to help regulate red blood cell production?

<p>Erythropoietin (C)</p> Signup and view all the answers

What is the significance of renal clearance in kidney function assessment?

<p>It assesses the efficiency of the kidneys in excreting substances. (B)</p> Signup and view all the answers

How do kidneys regulate plasma osmolarity?

<p>By adjusting the excretion of water in urine (D)</p> Signup and view all the answers

Which of the following is a direct consequence of increased plasma osmolarity?

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

What function do the kidneys perform in collaboration with the respiratory system?

<p>Regulating blood pH (B)</p> Signup and view all the answers

Which of the following electrolytes is the kidneys primarily responsible for regulating?

<p>Sodium (C)</p> Signup and view all the answers

What percentage of the filtrate produced is typically reabsorbed into the vascular compartment?

<p>99% (B)</p> Signup and view all the answers

Which nephron type constitutes the majority of nephrons in humans?

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

What is the average glomerular filtration rate (GFR) in humans?

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

Which tubular segment does filtrate enter after leaving Bowman’s capsule?

<p>Proximal convoluted tubule (D)</p> Signup and view all the answers

Which process involves the removal of additional substances from the blood into the nephron?

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

What is the function of peritubular capillaries?

<p>To converge and form larger veins (A)</p> Signup and view all the answers

Which part of the nephron allows for the most significant water reabsorption?

<p>Loop of Henle (A)</p> Signup and view all the answers

What is a characteristic of juxtamedullary nephrons?

<p>Associated with specialized vasa recta capillaries (A)</p> Signup and view all the answers

What is the primary purpose of reabsorption in the renal tubule?

<p>To return filtered substances to the bloodstream. (C)</p> Signup and view all the answers

How much filtrate is typically reabsorbed by the kidneys each day?

<p>178.5 L/day (B)</p> Signup and view all the answers

What does plasma clearance indicate about kidney function?

<p>The kidneys' ability to filter and process substances. (C)</p> Signup and view all the answers

Which of the following is NOT a criterion for a substance to be used in determining GFR via plasma clearance?

<p>It must be reabsorbed by the renal tubules. (B)</p> Signup and view all the answers

What is inulin as it relates to kidney function?

<p>A naturally occurring polysaccharide used to measure GFR. (C)</p> Signup and view all the answers

What is the average daily output of urine in relation to the amount of filtrate reabsorbed?

<p>1.5 L/day (C)</p> Signup and view all the answers

Which measurement is essential for calculating plasma clearance?

<p>Concentration of the substance in arterial plasma. (C)</p> Signup and view all the answers

What is the formula for plasma clearance when calculating GFR?

<p>C = (U * V) / P (D)</p> Signup and view all the answers

What does the plasma clearance of inulin indicate?

<p>It measures the GFR accurately. (D)</p> Signup and view all the answers

What is a key disadvantage of using creatinine for estimating GFR?

<p>It slightly overestimates GFR due to minor secretion. (A)</p> Signup and view all the answers

Which of the following substances is used to determine effective renal plasma flow (ERPF)?

<p>Para-aminohippuric acid (PAH) (D)</p> Signup and view all the answers

How does reabsorption affect the plasma clearance rate of a substance?

<p>Decreases plasma clearance rate to less than GFR. (A)</p> Signup and view all the answers

What is the average percentage of plasma filtered into the tubules at the glomerulus?

<p>20% (A)</p> Signup and view all the answers

What happens to plasma clearance if a substance is completely reabsorbed?

<p>It drops to below the GFR. (A)</p> Signup and view all the answers

Which of the following correctly describes filtration at the glomerulus?

<p>It establishes how much of the substance enters renal tubules. (A)</p> Signup and view all the answers

Why is inulin clearance considered inconvenient despite its accuracy?

<p>It necessitates continuous infusion over several hours. (B)</p> Signup and view all the answers

Flashcards

What is the primary function of the kidneys?

The kidneys are responsible for filtering blood and removing metabolic waste products like urea, uric acid, creatinine, and urobilinogen.

How do kidneys regulate extracellular fluid volume?

The kidneys regulate the volume and composition of extracellular fluid, including plasma volume and electrolyte concentrations.

How do kidneys help in maintaining acid-base balance?

The kidneys play a crucial role in maintaining acid-base balance, working in conjunction with the respiratory system.

What hormones and enzymes are produced by the kidneys?

The kidneys produce hormones like erythropoietin, which stimulates red blood cell production, and enzymes like renin, involved in regulating blood pressure.

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Describe the structure of the nephron.

The nephron is the functional unit of the kidney, responsible for filtering blood and producing urine. It consists of vascular components like the glomerulus and tubular components like the proximal tubule, loop of Henle, and distal tubule.

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What is the function of the glomerulus in the nephron?

The glomerulus filters blood, allowing small molecules like water, glucose, and electrolytes to pass through while retaining larger molecules like proteins.

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

The proximal tubule reabsorbs water, glucose, amino acids, and electrolytes back into the bloodstream, while secreting waste products.

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Define renal clearance and explain its significance.

Renal clearance refers to the volume of plasma that is completely cleared of a substance by the kidneys per unit time. It helps assess kidney function and the excretion of various substances.

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What do the kidneys excrete?

The kidneys remove substances like drugs, non-nutritive compounds, and pesticides, preventing their harmful accumulation in the body.

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How do kidneys balance blood pH?

When the blood is acidic, the kidneys excrete hydrogen ions (H+) and conserve bicarbonate (HCO3-), balancing the pH.

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What hormone does the kidney produce?

The kidneys produce erythropoietin, which stimulates red blood cell production in response to low oxygen levels. This hormone is crucial for oxygen transport in the blood.

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Where are the kidneys located?

The kidneys are located in the posterior abdominal wall, on either side of the vertebral column, slightly above the waistline.

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What is the functional unit of the kidney?

The functional unit of the kidney is the nephron, responsible for filtering blood and producing urine.

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What is the role of the peritubular capillaries?

The efferent arterioles, which carry unfiltered plasma and blood cells, branch into peritubular capillaries that nourish renal tissues and reabsorb substances from the nephron.

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What is the role of the efferent arterioles?

The efferent arterioles, which carry unfiltered plasma and blood cells, branch into peritubular capillaries that nourish renal tissues and reabsorb substances from the nephron.

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Peritubular capillaries

Peritubular capillaries are tiny blood vessels that wrap around the renal tubules, facilitating the exchange of substances between the blood and the fluid within the tubules.

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Filtration in the kidney

The process by which substances in the blood move from the glomerulus into Bowman's capsule, forming filtrate.

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Reabsorption in the kidney

The movement of substances from the filtrate back into the blood, primarily within the tubules of the nephron.

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Secretion in the kidney

The process by which substances move from the blood into the filtrate within the tubules, to be eliminated in urine.

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Cortical nephrons

These nephrons have shorter loops of Henle that only extend a short distance into the medulla.

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Juxtamedullary nephrons

These nephrons have longer loops of Henle that penetrate deeper into the medulla, playing a crucial role in concentrating urine.

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Glomerular filtration rate (GFR)

The rate at which plasma is filtered by the glomeruli, typically around 125 mL/min or 180 L/day.

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Renal clearance

The volume of plasma that is completely cleared of a substance by the kidneys per unit time. It helps assess the efficiency of kidney function for a specific substance.

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Reabsorption

The movement of filtered substances from the renal tubule back into the bloodstream. It occurs throughout the renal tubule and plays a crucial role in preserving valuable nutrients and water.

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Secretion

The movement of selected unfiltered substances from the peritubular capillaries into the renal tubule. This process helps eliminate waste products and regulate blood pH.

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Renal/Plasma Clearance

A measure of the kidneys' efficiency in removing substances from the blood. It represents the volume of plasma completely cleared of a substance by the kidneys per unit of time.

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Effective Renal Plasma Flow (ERPF)

The volume of plasma effectively perfused through the kidneys. It reflects the amount of blood flow available for filtration and excretion.

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Requirements for Using Plasma Clearance to Determine GFR

The plasma clearance of a substance can be used to determine the GFR if the substance is freely filtered at the glomerulus, not reabsorbed or secreted by the tubules, and doesn't affect the GFR.

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Inulin: A Marker for GFR

Inulin is a polysaccharide that meets the criteria for determining GFR. It's administered intravenously, and its concentration in urine and plasma is measured to calculate the GFR.

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Clinical Significance of Plasma Clearance

Plasma clearance calculations help assess kidney function, identify renal impairment, monitor disease progress, and establish baseline measurements for starting certain drug treatments.

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Inulin

A substance that is filtered through the glomerulus, but not reabsorbed or secreted, and its clearance equals the GFR. Useful for measuring the GFR.

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Creatinine

An end product of muscle metabolism. It is a good alternative for estimating GFR, but slightly overestimates due to some secretion in the tubules.

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Filtration Fraction

The percentage of blood plasma flowing through the glomerulus that is filtered into the tubules. It reflects how much fluid the kidneys process.

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Para-aminohippuric acid (PAH)

A substance readily filtered by the glomerulus and secreted by the tubules. It is useful for measuring ERPF due to its complete clearance.

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Filtration

The process by which substances in the blood move from the glomerulus into Bowman's capsule, forming filtrate. This is the initial step in urine formation.

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Study Notes

Kidney Functions and Renal Clearance

  • Kidneys are vital organs responsible for filtering blood, removing metabolic waste, and maintaining fluid and electrolyte balance.
  • Key functions include:
    • Regulating extracellular fluid volume and osmolarity.
    • Regulating inorganic electrolyte concentrations (e.g., sodium, potassium, calcium).
    • Removing metabolic waste products (e.g., urea, uric acid, creatinine, urobilinogen).
    • Excreting foreign compounds (e.g., drugs, pesticides, food additives).
    • Maintaining acid-base balance in conjunction with the respiratory system.
    • Producing hormones (e.g., erythropoietin) and enzymes (e.g., renin).
    • Maintaining blood pressure.
    • Producing red blood cells.

Renal Clearance

  • Renal clearance is a measure of the kidneys' effectiveness in removing substances from the blood.
  • It's calculated as the volume of plasma completely cleared of a substance by the kidneys per unit time, typically measured in mL/min.
  • The use of renal clearance is important in assessing kidney function.

Basic Renal Processes

  • Three primary processes:
    • Filtration: The process of filtering fluid and solutes from plasma into the nephron.
      • This occurs in the glomerulus.
      • Non-selective process.
      • About 20% of plasma is filtered.
      • Average glomerular filtration rate (GFR): 125 mL/min or 180 L/day of filtrate.
    • Reabsorption: Returns essential substances and water to the bloodstream.
      • Occurs throughout the renal tubule.
      • Approximately 99% of filtrate is reabsorbed.
      • Results in average urine output of about 1.5 L/day.
    • Secretion: Removes additional substances from the blood into the nephron for excretion.
      • Movement of selected unfiltered substances.

Types of Nephrons

  • Two main types:
    • Cortical Nephrons: Located in the outer cortex; short loops of Henle.
    • Juxtamedullary Nephrons: Located near the medulla; long loops of Henle.

Important Substances for GFR Determination

  • Inulin is a polysaccharide found in plants, used to calculate GFR.
  • Creatinine is a breakdown product of muscle metabolism; measures GFR, but slightly overestimates it due to minor secretion into urine.
  • Para-aminohippuric acid (PAH): used to determine effective renal plasma flow (ERPF).

Factors Affecting Renal Clearance

  • Filtration at glomerulus.
  • Reabsorption.
  • Secretion.

Filtration Fraction

  • Represents the percentage of plasma filtered into the tubules.
  • Calculated as GFR divided by ERPF.
  • The average is 20%.

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PPBM1321 Functions of Kidney PDF

Description

Test your knowledge about the functions of the kidneys, including waste excretion, hormone production, and regulation of blood pressure and pH. This quiz covers various aspects of kidney physiology and the nephron's role in maintaining homeostasis in the body.

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