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Questions and Answers
Which of the following is NOT a primary function of the kidneys?
Which of the following is NOT a primary function of the kidneys?
- Regulating the volume of extracellular fluid (ECF).
- Regulating the composition of extracellular fluid (ECF).
- Eliminating potentially toxic metabolic wastes.
- Regulating body temperature through sweat production. (correct)
Which of the following best describes the location of kidneys in the human body?
Which of the following best describes the location of kidneys in the human body?
- Under the spine and under the ribcage.
- Inside the ribcage, on either side of the spine.
- Superior to the ribcage, close to the diaphragm.
- Outside the ribcage, on either side of the spine. (correct)
Which of the following statements accurately describes the flow of urine after it leaves the kidneys?
Which of the following statements accurately describes the flow of urine after it leaves the kidneys?
- Urine is directly eliminated out of the kidney through the urethra.
- Urine travels down the ureter and is stored in the bladder. (correct)
- Urine travels through the bladder and is stored in the ureter, before elimination.
- Urine travels through the urethra to the ureter and is stored in the bladder.
What role does the kidney play in relation to Vitamin D?
What role does the kidney play in relation to Vitamin D?
Which of the following options is NOT a function of the kidneys?
Which of the following options is NOT a function of the kidneys?
What is the main factor determining plasma and ECF osmolarity?
What is the main factor determining plasma and ECF osmolarity?
How does the body respond to conditions that cause ECF salt and water levels to rise?
How does the body respond to conditions that cause ECF salt and water levels to rise?
Which of the following statements best describes the role of the kidneys in maintaining body fluid composition?
Which of the following statements best describes the role of the kidneys in maintaining body fluid composition?
What substances can freely exchange between plasma and interstitial fluid?
What substances can freely exchange between plasma and interstitial fluid?
What is the functional unit of the kidney?
What is the functional unit of the kidney?
Which two main components make up each nephron?
Which two main components make up each nephron?
What is the primary function of the glomerulus?
What is the primary function of the glomerulus?
Where does filtrate formation take place in the kidney?
Where does filtrate formation take place in the kidney?
Which of the following is the correct sequence of tubular components in the nephron?
Which of the following is the correct sequence of tubular components in the nephron?
Which section of the nephron establishes an osmotic gradient in the renal medulla?
Which section of the nephron establishes an osmotic gradient in the renal medulla?
What process occurs in the Proximal Convoluted Tubule (PCT)?
What process occurs in the Proximal Convoluted Tubule (PCT)?
Which is NOT a basic process performed by the nephron to make urine?
Which is NOT a basic process performed by the nephron to make urine?
Which process describes the movement of substances from the peritubular capillaries into the tubular lumen?
Which process describes the movement of substances from the peritubular capillaries into the tubular lumen?
What are the primary components of the filtrate that enter Bowman's capsule?
What are the primary components of the filtrate that enter Bowman's capsule?
Approximately what percentage of the initial filtrate volume is reabsorbed back into the bloodstream?
Approximately what percentage of the initial filtrate volume is reabsorbed back into the bloodstream?
What process mainly occurs when a substance in tubular reabsorption is ‘active’?
What process mainly occurs when a substance in tubular reabsorption is ‘active’?
What are the two main functions of peritubular capillaries?
What are the two main functions of peritubular capillaries?
What force drives ultrafiltration in the glomerulus?
What force drives ultrafiltration in the glomerulus?
If a person's kidneys produce approximately 1.5 liters of urine per day, how much filtrate is reabsorbed?
If a person's kidneys produce approximately 1.5 liters of urine per day, how much filtrate is reabsorbed?
How does the kidneys maintaining water balance affect osmolarity in the plasma/ECF?
How does the kidneys maintaining water balance affect osmolarity in the plasma/ECF?
Which accurately describes the path a substance takes during transepithelial transport for reabsorption?
Which accurately describes the path a substance takes during transepithelial transport for reabsorption?
If the plasma osmolarity is normally maintained at $283 \pm 11$ mosmol/L, what is the approximate range maintained by the body?
If the plasma osmolarity is normally maintained at $283 \pm 11$ mosmol/L, what is the approximate range maintained by the body?
How can the change in levels of NaCl affect the change of water levels in the body?
How can the change in levels of NaCl affect the change of water levels in the body?
Which of the following options are the kidneys responsible for?
Which of the following options are the kidneys responsible for?
In a healthy individual, what substances are NOT typically found in the filtrate?
In a healthy individual, what substances are NOT typically found in the filtrate?
Why is it important to maintain constant osmolarity of cell fluid?
Why is it important to maintain constant osmolarity of cell fluid?
Which of the following processes best describes the role of the kidney in homeostasis?
Which of the following processes best describes the role of the kidney in homeostasis?
What occurs when the volume of the body fluid increases?
What occurs when the volume of the body fluid increases?
What processes do the kidneys have to keep acid-base balance?
What processes do the kidneys have to keep acid-base balance?
How much blood flow (RBF) do the kidneys need?
How much blood flow (RBF) do the kidneys need?
How much amount of blood flows to a kidney?
How much amount of blood flows to a kidney?
What forms from renal arteries?
What forms from renal arteries?
What happens after the glomerular recombine?
What happens after the glomerular recombine?
What does the process of tubular reabsorption do?
What does the process of tubular reabsorption do?
What is released after urine is formed after it is the last 'product' of the nephron?
What is released after urine is formed after it is the last 'product' of the nephron?
Which of the following scenarios would result in the greatest increase in plasma osmolarity, assuming all other factors remain constant?
Which of the following scenarios would result in the greatest increase in plasma osmolarity, assuming all other factors remain constant?
If the afferent arteriole constricts, how will the glomerular filtration rate (GFR) be directly affected?
If the afferent arteriole constricts, how will the glomerular filtration rate (GFR) be directly affected?
Considering the functions of the kidney, which of the following patients would likely benefit from erythropoietin-stimulating agents?
Considering the functions of the kidney, which of the following patients would likely benefit from erythropoietin-stimulating agents?
How is the countercurrent multiplier system crucial for the kidney's function?
How is the countercurrent multiplier system crucial for the kidney's function?
What would be the physiological consequence of a drug that inhibits the Na+/K+ ATPase pump in the basolateral membrane of the proximal tubule cells?
What would be the physiological consequence of a drug that inhibits the Na+/K+ ATPase pump in the basolateral membrane of the proximal tubule cells?
Which of the following options is NOT correct regarding the role of the kidneys?
Which of the following options is NOT correct regarding the role of the kidneys?
What effect does increased aldosterone secretion have on potassium and sodium levels in the urine?
What effect does increased aldosterone secretion have on potassium and sodium levels in the urine?
What would happen if the filtration fraction increases significantly above normal?
What would happen if the filtration fraction increases significantly above normal?
Which statement defines how the kidneys maintain water balance?
Which statement defines how the kidneys maintain water balance?
Which factor has major importance in determining plasma and ECF osmolarity?
Which factor has major importance in determining plasma and ECF osmolarity?
Under what circumstance would the kidneys increase the excretion of both sodium and water?
Under what circumstance would the kidneys increase the excretion of both sodium and water?
Which of the following physiological responses would occur if the osmolarity of the ECF decreased?
Which of the following physiological responses would occur if the osmolarity of the ECF decreased?
Besides the kidneys, which of the following factors maintains body fluid composition?
Besides the kidneys, which of the following factors maintains body fluid composition?
Which of the following has free exchange between plasma and interstitial fluid?
Which of the following has free exchange between plasma and interstitial fluid?
Which structure is the nephron's primary site for regulating the final osmolarity of urine?
Which structure is the nephron's primary site for regulating the final osmolarity of urine?
Which two main components that make up each nephron have different functions?
Which two main components that make up each nephron have different functions?
What is ultrafiltration, the 'first step' of the glomerulus primarily responsible for?
What is ultrafiltration, the 'first step' of the glomerulus primarily responsible for?
Where does the filtrate formation take place?
Where does the filtrate formation take place?
Which tubular component of the nephron uses hair-pin-like loops that descend into the medulla?
Which tubular component of the nephron uses hair-pin-like loops that descend into the medulla?
The process of secretion that mainly occurs in the Proximal Convoluted Tubule (PCT) is primarily for what?
The process of secretion that mainly occurs in the Proximal Convoluted Tubule (PCT) is primarily for what?
Which process does NOT occur in the nephron to make urine?
Which process does NOT occur in the nephron to make urine?
What happens during tubular secretion?
What happens during tubular secretion?
What are the primary components of the filtrate entering Bowman's capsule?
What are the primary components of the filtrate entering Bowman's capsule?
What percentage of the initial filtrate volume is reabsorbed back into the bloodstream?
What percentage of the initial filtrate volume is reabsorbed back into the bloodstream?
What is characteristic of 'active' tubular reabsorption?
What is characteristic of 'active' tubular reabsorption?
What are some functions of peritubular capillaries?
What are some functions of peritubular capillaries?
What is ultrafiltration primarily driven by in the glomerulus?
What is ultrafiltration primarily driven by in the glomerulus?
If 180 liters of filtrate are formed per day, and 1.5 liters of urine are excreted, how much filtrate is reabsorbed?
If 180 liters of filtrate are formed per day, and 1.5 liters of urine are excreted, how much filtrate is reabsorbed?
How does water balance contribute to maintaining appropriate levels of osmolarity in the plasma/ECF?
How does water balance contribute to maintaining appropriate levels of osmolarity in the plasma/ECF?
What is the path a substance takes during transepithelial transport for reabsorption?
What is the path a substance takes during transepithelial transport for reabsorption?
Plasma osmolarity is typically maintained at $283 \pm 11$ mosmol/L. What is the range?
Plasma osmolarity is typically maintained at $283 \pm 11$ mosmol/L. What is the range?
What effect does a substantial increase in NaCl levels have on water levels in the body?
What effect does a substantial increase in NaCl levels have on water levels in the body?
What function are the kidneys NOT responsible for?
What function are the kidneys NOT responsible for?
What substances are NOT found in the filtrate of healthy individuals?
What substances are NOT found in the filtrate of healthy individuals?
Why is it important that the cell fluid has constant osmolarity?
Why is it important that the cell fluid has constant osmolarity?
In homeostasis, which process does the kidney NOT perform?
In homeostasis, which process does the kidney NOT perform?
Which physiological event is MOST directly triggered by an increase in the volume of body fluid?
Which physiological event is MOST directly triggered by an increase in the volume of body fluid?
To keep acid-base balance what processes do the kidneys perform?
To keep acid-base balance what processes do the kidneys perform?
What is expected blood flow (RBF) that kidney requires to function?
What is expected blood flow (RBF) that kidney requires to function?
Renal arteries give rise to ______________.
Renal arteries give rise to ______________.
What happens after glomerular capillaries recombine?
What happens after glomerular capillaries recombine?
What is the purpose of tubular reabsorption?
What is the purpose of tubular reabsorption?
What is the name of the product that urine is finalized as?
What is the name of the product that urine is finalized as?
Flashcards
Primary Kidney Function
Primary Kidney Function
The kidneys regulate the volume and composition of extracellular fluid.
Water Balance
Water Balance
Kidneys maintain the correct amount of water in the body.
Osmolarity
Osmolarity
Kidneys maintain the right concentration of solutes in body fluids.
Ionic Regulation
Ionic Regulation
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Kidney Excretions
Kidney Excretions
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Vitamin D Activation
Vitamin D Activation
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Erythropoietin Production
Erythropoietin Production
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Extracellular Fluid (ECF)
Extracellular Fluid (ECF)
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Intracellular Fluid (ICF)
Intracellular Fluid (ICF)
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Fluid Exchange
Fluid Exchange
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Normal Plasma Osmolarity
Normal Plasma Osmolarity
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ECF Change Tendency
ECF Change Tendency
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Nephron
Nephron
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Nephrons per Kidney
Nephrons per Kidney
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Renal Corpuscle
Renal Corpuscle
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Tubular System
Tubular System
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Bowman's Capsule
Bowman's Capsule
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Proximal Convoluted Tubule (PCT)
Proximal Convoluted Tubule (PCT)
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Loop of Henle
Loop of Henle
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Distal Convoluted Tubule (DCT)
Distal Convoluted Tubule (DCT)
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Collecting Duct
Collecting Duct
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Nephron Processes
Nephron Processes
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Basic Processes by Nephron
Basic Processes by Nephron
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Ultrafiltration
Ultrafiltration
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Filtration Barrier
Filtration Barrier
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Volume of Tubular Filtrate Formed
Volume of Tubular Filtrate Formed
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Urine output daily
Urine output daily
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Filtrate Reabsorption
Filtrate Reabsorption
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Tubular Reabsorption
Tubular Reabsorption
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Transepithelial Transport
Transepithelial Transport
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Proximal Tubule Reabsorption
Proximal Tubule Reabsorption
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Distal Tubules Reabsorption
Distal Tubules Reabsorption
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Tubular Secretion
Tubular Secretion
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Urine formed per minute
Urine formed per minute
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Key Function
Key Function
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Kidney Structure
Kidney Structure
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Kidney Primary Functions
Kidney Primary Functions
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Kidney Blood Supply
Kidney Blood Supply
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Afferent Arterioles
Afferent Arterioles
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Efferent Arterioles
Efferent Arterioles
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Peritubular Capillaries
Peritubular Capillaries
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Capillaries Function
Capillaries Function
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Loop of Henle Reabsorption
Loop of Henle Reabsorption
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Urine Composition
Urine Composition
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Kidney Functions
Kidney Functions
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Study Notes
Introduction to the Kidney
- The renal system module is MED 204.
- The lecturers are Prof David Henshall & Dr. Patrick Walsh.
- The date of the module is February 2025.
- A main function of the kidneys is to maintain homeostasis
Overview of Functions
- Key functions involve kidney function, body fluid composition, the nephron, and urine formation.
Kidney Functions & Homeostasis
- Kidneys are key for homeostasis
- Kidneys ensure correct water levels in the body
- Kidneys regulate blood pressure
- Kidneys remove wastes like urea, uric acid, and toxins via urine
- Kidneys activate vitamin D which aids in calcium absorption
- Kidneys maintain acid-base balance
- Kidneys regulate the balance of electrolytes for heart rhythm
- Kidneys release erythropoietin, telling bone marrow to make red blood cells.
Kidney Structure
- Kidneys are bean-shaped organs on either side of the spine under the ribcage.
- Kidneys remove waste and water from blood to produce urine.
- Urine travels down the ureter and is stored in the bladder.
- Kidneys are bilateral retroperitoneal organs, receiving blood from the renal artery and vein.
- The filtrate forms in Bowman's capsule in the cortex and urine flows from collecting ducts into calyces.
Primary Kidney Functions
- Kidneys regulate the volume and composition of extracellular fluid (ECF).
- Kidneys regulate the volume and composition of the plasma that then results in regulation of volume and composition of the entire ECF
- Kidneys eliminate potentially toxic metabolic wastes and foreign compounds.
- Kidneys maintain water balance in the body
- Proper plasma volume involves the regulation of blood pressure.
- Osmolarity is maintained by regulating water balance.
- Kidneys regulate the quantity and concentration of extracellular fluid ions like Na+, K+, Cl-, Ca2+, and PO43-.
- Acid-base balance is also maintained alongside pH.
- Kidneys excrete waste products of metabolism, including urea (from amino acids) and uric acid (from nucleic acids).
- Kidneys also excrete drugs and food additives.
- Vitamin D is converted to its active form by proximal tubule cells for calcium regulation.
- Erythropoietin is produced in the interstitium of the cortex/outer medulla; this hormone stimulates red blood cell production.
Body Fluid Composition
- Water accounts for 60% of body mass where 2/3 of that is intracellular and 1/3 is extracellular
- Extracellular fluid is the fluid outside cells, consisting of plasma and interstitial fluid.
- Plasma surrounds blood cells and interstitial fluid surrounds cells of all other tissues.
- There is free exchange of water and solutes, except proteins, between plasma and interstitial fluid across capillary walls.
- Fluid distribution relies on hydrostatic and osmotic forces.
- Changes in composition will affect cell physiology.
- Plasma osmolarity is mainly determined by NaCl content relative to water content.
- A decrease in water increases osmolarity, and an increase in water lowers osmolarity.
- Kidneys maintain water balance to keep plasma/ECF osmolarity constant.
- 1 mmol free ions = 1 mosmol
- Plasma and ECF osmolarity is normally constant at 283 ± 11 mosmol/l, maintaining cell fluid osmolarity.
- Ingesting foods with salts and water and exercise can affect salt and water levels.
- Other factors like vomiting and diarrhoea can affect salt and water balance in the body
- Kidneys counterbalance this by excreting appropriate amounts of salt and water.
Nephron Structure & Function
- The nephron is the kidney's functional unit, with 1-1.2 million nephrons per kidney.
- The two main components are the renal corpuscle and the tubular system.
- The renal corpuscle includes a tuft of capillaries and Bowman's capsule
- The tubular system is fluid filled tube with one layer of epithelial cells and a vascular supply
- Bowman's Capsule collects glomerular filtrate.
- The Proximal Convoluted Tubule (PCT) is where absorption and secretion of selected substances occurs.
- The Loop of Henle establishes an osmotic gradient in the renal medulla where ascending and descending loops have different channels/functions
- Distal Convoluted Tubule (DCT) controls the reabsorption of Na+ and water, plus secretion of K+ and H+.
- The collecting duct transports fluid (urine) to the renal pelvis.
- The major processes performed by the nephron are filtration, tubular reabsorption, and tubular secretion.
- The first process in the nephron is ultrafiltration of the plasma in the glomerulus, dependent on hydrostatic pressure.
- Blood supply to the two kidneys is via the renal arteries.
- Kidney blood flow is approximately 1.2 L/min.
- This renal blood flow equals ~1/5 of cardiac output.
- The renal artery subdivides into afferent arterioles, each supplying a nephron.
- Glomerular capillaries recombine, exiting Bowman's capsule as efferent arterioles.
- Efferent arterioles give rise to peritubular capillaries around the tubular system.
- These capillaries then recombine to form venules and the renal vein.
- Peritubular capillaries are nutritive, reabsorptive, and secretive.
Glomerular Filtration
- Plasma filters from the blood into Bowman’s capsule and 20% of components are filtered out.
- The filtrate then flows through the tubular system
Filtration Barrier & Filtrate Composition
- All components of plasma, except cells and proteins, pass through.
- Useful substances, as well as wastes, pass through.
- Approximately 180 liters of filtrate form daily, “treating” the entire ECF ~10 times.
- From this, approximately 1.5 liters of urine are excreted.
- About 178.5 liters of filtrate is reabsorbed per day.
Tubular Reabsorption
- It is highly selective and variable.
- Tubules have high reabsorptive capacity for needed substances.
- There is little capacity for useless/harmful substances.
- Overall, 99% of what's filtered is reabsorbed, including 99% of water, 100% of glucose, and 99.5% of salt.
- Tubular reabsorption can be active (energy requiring) or passive.
- Active transport requires energy (ATP) expenditure, like glucose, amino acids, and Na+.
- Passive transport occurs down electrochemical or osmotic gradients, like water and chloride ions.
- Substance leaves tubular fluid, passes through the cytosol of tubular cell, crosses basolateral membrane, diffuses through interstitial space, and penetrates capillary wall to enter blood plasma
Reabsorption & Secretion Details
- Na+ reabsorption involves diffusion, ATP, and interstitial fluids.
- Proximal tubule reabsorbs about 67% of Na+ and 65% of H2O.
- Loop of Henle reabsorbs about 25% of Na+ and 15% of H2O.
- Distal tubule and collecting tubules reabsorb approximately 8% of Na+ and 20% of H2O.
- Tubular secretion transports substances from peritubular capillaries into the tubular lumen.
- This secretion includes H+, potassium, organic ions, drugs, food additives, and environmental pollutants.
Urine & Learning Outcomes
- Urine is the kidney's final "product," approximately 1ml/min.
- Urine includes H2O, urea, creatinine, ions, and phenol.
- Urine is slightly acidic (pH 6.0 approx).
- Urine osmolarity varies (50-1200 mOsm) based on water levels.
- Main functions of the kidneys can be explained
- The basic tubular and vascular system of the nephron can be described
- Thee processes performed by the nephron to produce urine can be explained
- Body fluid composition can be described
- The normal volume and composition of urine can be defined
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Description
Overview of kidney functions, including homeostasis, water levels, and blood pressure regulation. Covers waste removal, vitamin D activation, and electrolyte balance. Explains the kidney's bean-shaped structure and its role in urine production.
