Glomerular Filtration

What occurs during glomerular filtration?
A) Urine is expelled from the body
B) Nutrients are absorbed into the filtrate
C) Blood is filtered from the glomerulus to form filtrate
D) Water is reabsorbed from the ureter

C) Blood is filtered from the glomerulus to form filtrate

Where does glomerular filtration take place?
A) Loop of Henle
B) Renal pelvis
C) Renal corpuscle
D) Collecting duct

C) Renal corpuscle

What happens during tubular reabsorption?
A) Blood cells are filtered out of plasma
B) Solutes are removed from the filtrate and returned to the blood
C) Water is added to filtrate
D) Urine is stored in the bladder

B) Solutes are removed from the filtrate and returned to the blood

Where does tubular reabsorption occur?
A) Renal tubule
B) Glomerulus
C) Ureter
D) Renal capsule

A) Renal tubule

What occurs during tubular secretion?
A) Urine is filtered out of the body
B) Blood cells are absorbed by the nephron
C) Additional substances are removed from the blood and added to the filtrate
D) Proteins are reabsorbed into the nephron

C) Additional substances are removed from the blood and added to the filtrate

Tubular secretion primarily occurs in which part of the nephron?
A) Glomerulus
B) Renal pelvis
C) Renal tubule
D) Urethra

C) Renal tubule

What is the goal of the water conservation stage of urine formation?
A) Increase the volume of filtrate
B) Reabsorb water from filtrate back into the blood
C) Eliminate all solutes
D) Produce concentrated bile

B) Reabsorb water from filtrate back into the blood

Where does water conservation occur in the nephron?
A) Bowman’s capsule
B) Afferent arteriole
C) Renal tubule and collecting duct
D) Glomerulus and urethra

C) Renal tubule and collecting duct

What is glomerular filtration?
A) The process of reabsorbing solutes into the nephron
B) The first stage of urine formation, where blood is filtered at the glomerulus
C) A stage in digestive enzyme release
D) The movement of urine through the ureters

B) The first stage of urine formation, where blood is filtered at the glomerulus

Where do filtered substances go after leaving the glomerulus?
A) Distal convoluted tubule
B) Bowman’s (glomerular) capsule
C) Renal pelvis
D) Loop of Henle

B) Bowman’s (glomerular) capsule

Which structures make up the filtration membrane in the renal corpuscle?
A) Basement membrane, afferent arteriole, and renal pelvis
B) Capillary endothelium, basement membrane, and filtration slits
C) Collecting duct, nephron loop, and cortex
D) Podocytes, vasa recta, and Bowman's capsule

B) Capillary endothelium, basement membrane, and filtration slits

What feature of the capillary endothelium allows filtration?
A) Mucus secretion
B) Smooth muscle contraction
C) Fenestrations that permit movement of substances smaller than 70 nm
D) Negatively charged barrier

C) Fenestrations that permit movement of substances smaller than 70 nm

What is a key characteristic of the basement membrane in the filtration membrane?
A) Positively charged and permeable to large proteins
B) Negatively charged and allows neutral or positively charged molecules smaller than 8 nm
C) Lined with smooth muscle
D) Forms the wall of the renal tubule

B) Negatively charged and allows neutral or positively charged molecules smaller than 8 nm

What are filtration slits and where are they found?
A) Gaps between capillary walls that reabsorb glucose
B) Openings between foot processes of podocytes that allow passage into the capsular space
C) Spaces in the ureter allowing urine flow
D) Holes in the collecting duct for salt excretion

B) Openings between foot processes of podocytes that allow passage into the capsular space

Which of the following substances are normally found in the filtrate?
A) Red blood cells and proteins
B) Only water
C) Water, glucose, amino acids, fatty acids, nitrogenous wastes, salts
D) Hormones and bile

C) Water, glucose, amino acids, fatty acids, nitrogenous wastes, salts

Why are blood cells and most proteins not found in the filtrate?
A) They are metabolized too quickly
B) They are filtered but quickly reabsorbed
C) Both are too large and protein negatively charged to pass through the filtration membrane
D) They are dissolved in urine

C) Both are too large and protein negatively charged to pass through the filtration membrane

What does glomerular filtration rate (GFR) measure?
A) Blood pressure in the renal artery
B) Amount of urine stored in the bladder
C) Amount of filtrate produced by both kidneys per minute
D) Volume of water absorbed by the intestines

C) Amount of filtrate produced by both kidneys per minute

What is the average glomerular filtration rate (GFR) for a healthy adult male?
A) 80 mL/min
B) 100 mL/min
C) 125 mL/min
D) 140 mL/min

C) 125 mL/min

What is the average GFR for a healthy adult female?
A) 105 mL/min
B) 115 mL/min
C) 95 mL/min
D) 125 mL/min

A) 105 mL/min

How many times per day does the kidney filter the entire human blood volume?
A) 5–10 times
B) 15–20 times
C) 25–30 times
D) 50–60 times

D) 50–60 times

Approximately how much filtrate do the kidneys produce in one day?
A) 10–20 liters
B) 50–75 liters
C) 150–180 liters
D) 300–350 liters

C) 150–180 liters

What percentage of the filtrate produced by the kidneys is reabsorbed into the blood?
A) 90%
B) 99%
C) 75%
D) 50%

B) 99%

n: Despite producing up to 180 L of filtrate per day, how much urine is typically excreted?
A) 0.5–1 L
B) 1–2 L
C) 3–4 L
D) 5–6 L

B) 1–2 L

Why is it important to regulate the glomerular filtration rate (GFR)?
A) To maintain hormone production
B) To prevent the buildup or loss of essential substances in the body
C) To promote urine storage
D) To activate white blood cells

B) To prevent the buildup or loss of essential substances in the body

What is a consequence of an excessively high GFR?
A) Wastes are not removed from blood
B) Too much reabsorption of solutes
C) Fluid flows too quickly through the renal tubule for proper reabsorption
D) Reduced urine output

C) Fluid flows too quickly through the renal tubule for proper reabsorption

A persistently high GFR can lead to:
A) Increased protein synthesis
B) Dehydration due to increased urination
C) Kidney stone formation
D) Filtrate retention in the ureters

B) Dehydration due to increased urination

What may happen if the GFR is too low?
A) Excessive urination
B) Wastes are not adequately removed from blood or reabsorbed
C) Overhydration
D) Increased blood filtration

B) Wastes are not adequately removed from blood or reabsorbed

How is GFR primarily regulated?
A) By increasing blood volume
B) By controlling urine acidity
C) By adjusting glomerular blood pressure
D) By regulating ureter size

C) By adjusting glomerular blood pressure

How does increased glomerular blood pressure affect GFR?
A) Decreases GFR by reducing filtration
B) Has no effect on GFR
C) Increases blood osmolarity
D) Increases hydrostatic pressure, thereby increasing net filtration pressure and GFR

D) Increases hydrostatic pressure, thereby increasing net filtration pressure and GFR

Which of the following represents the correct formula for Net Filtration Pressure (NFP)?
A) NFP = CP + COP - BHP
B) NFP = (COP × CP) ÷ BHP
C) NFP = BHP - (CP + COP)
D) NFP = BHP + COP + CP

C) NFP = BHP - (CP + COP)

What is the typical Net Filtration Pressure (NFP) in the glomerulus?
A) 0 mmHg
B) 5 mmHg
C) 10 mmHg
D) 20 mmHg

C) 10 mmHg

What does blood hydrostatic pressure (BHP) in the glomerulus do?
A) Favors reabsorption
B) Favors filtration
C) Prevents protein leakage
D) Lowers GFR

B) Favors filtration

Why is the blood hydrostatic pressure (BHP) particularly high in the glomerulus?
A) Because of high blood glucose levels
B) Because of smaller Bowman's capsule
C) Because the afferent arteriole is wider than the efferent arteriole
D) Because of water retention in the tubules

C) Because the afferent arteriole is wider than the efferent arteriole

What is the role of capsular hydrostatic pressure (CP)?
A) Promotes urine formation
B) Favors reabsorption caused by filtrate in capsular space
C) Enhances blood pressure
D) Removes toxins from the blood

B) Favors reabsorption caused by filtrate in capsular space

What causes blood colloid osmotic pressure (COP), and what does it favor?
A) Caused by urea; favors filtration
B) Caused by white blood cells; favors urine formation
C) Caused by proteins in plasma; favors reabsorption
D) Caused by salts in the nephron; favors secretion

C) Caused by proteins in plasma; favors reabsorption

What are the mechanisms of GFR Regulation

• Renal autoregulation

• Sympathetic control

What is the purpose of renal autoregulation in glomerular filtration?
A) To regulate body temperature
B) To allow nephrons to adjust their own blood flow and stabilize GFR
C) To increase urine concentration
D) To stimulate hormone release from the adrenal gland

B) To allow nephrons to adjust their own blood flow and stabilize GFR

Which two mechanisms are involved in renal autoregulation of GFR?
A) Sympathetic control and vasodilation
B) Renin secretion and aldosterone action
C) Myogenic mechanism and tubuloglomerular feedback
D) Osmosis and active transport

C) Myogenic mechanism and tubuloglomerular feedback

What is the main function of the myogenic mechanism in renal autoregulation?
A) To promote long-term blood pressure increase
B) To prevent sudden increases in systemic blood pressure from causing a large rise in GFR
C) To regulate hormone levels in the blood
D) To increase oxygen delivery to the kidney

B) To prevent sudden increases in systemic blood pressure from causing a large rise in GFR

What happens when the smooth muscle in afferent arterioles is stretched due to high blood pressure?
A) It dilates, increasing GFR
B) It contracts, restricting blood flow into the glomerulus
C) It bursts, leading to renal damage
D) It allows more blood to enter the renal vein

B) It contracts, restricting blood flow into the glomerulus

What is the correct sequence of events following a sudden rise in systemic blood pressure?
A) Afferent arterioles dilate → more blood to glomerulus → higher GFR
B) Afferent arterioles stretch → contract → reduced blood flow → lower glomerular BP and GFR
C) Glomerulus shrinks → filtrate increases
D) Renal capsule expands → urine output stops

B) Afferent arterioles stretch → contract → reduced blood flow → lower glomerular BP and GFR

What is the outcome of afferent arteriole contraction in response to high systemic blood pressure?
A) Increased glomerular blood pressure and GFR
B) No change in filtration rate
C) Lower glomerular blood pressure and GFR (closer to baseline)
D) Cessation of urine formation

C) Lower glomerular blood pressure and GFR (closer to baseline)

What happens if there is a sudden decrease in systemic blood pressure?
A) Afferent arterioles constrict to conserve blood
B) Afferent arterioles relax to increase blood flow to the glomerulus
C) Filtration stops completely
D) GFR remains elevated

B) Afferent arterioles relax to increase blood flow to the glomerulus

What is the role of tubuloglomerular feedback in the kidney?
A) To store urine in the renal pelvis
B) To regulate filtration by monitoring and responding to the condition of tubular fluid
C) To control blood glucose levels
D) To stimulate hormone release from the adrenal glands

B) To regulate filtration by monitoring and responding to the condition of tubular fluid

Where is the macula densa located and what does it detect?
A) In the ureter; detects blood pressure
B) In the renal pelvis; detects urine volume
C) In the nephron loop before the DCT; detects NaCl concentration in filtrate
D) In the collecting duct; detects glucose levels

C) In the nephron loop before the DCT; detects NaCl concentration in filtrate

What does the macula densa do when GFR is too high and NaCl levels in the filtrate increase?
A) Stimulates water retention in the bladder
B) Signals the brain to lower blood pressure
C) Stimulates juxtaglomerular (granular) cells
D) Inhibits aldosterone release

C) Stimulates juxtaglomerular (granular) cells

What are juxtaglomerular (granular) cells?
A) Epithelial cells in the DCT
B) Sensory neurons in the cortex
C) Modified smooth muscle cells around the afferent arteriole
D) White blood cells in the nephron

C) Modified smooth muscle cells around the afferent arteriole

What happens when juxtaglomerular cells are stimulated by the macula densa?
A) They dilate to increase filtration
B) They release NaCl into the filtrate
C) They constrict the afferent arteriole
D) They produce bile

C) They constrict the afferent arteriole

What is the effect of afferent arteriole constriction on glomerular filtration?
A) Increases blood flow and raises GFR
B) Decreases blood flow to the glomerulus, lowering glomerular BP and GFR
C) Dilates the collecting duct
D) Stimulates aldosterone release

B) Decreases blood flow to the glomerulus, lowering glomerular BP and GFR

What triggers vasoconstriction of afferent arterioles during sympathetic control of the kidneys?
A) Parasympathetic stimulation and aldosterone
B) Increased antidiuretic hormone (ADH) levels
C) Sympathetic innervation and catecholamines (e.g., epinephrine) from the adrenal medulla
D) High levels of insulin and glucagon

C) Sympathetic innervation and catecholamines from the adrenal medulla

What is the effect of vasoconstriction of the afferent arterioles on kidney function?
A) Increases glomerular filtration rate (GFR)
B) Enhances sodium reabsorption in the nephron
C) Decreases blood flow to the glomerulus, lowering glomerular BP and GFR
D) Stimulates the release of insulin from the pancreas

C) Decreases blood flow to the glomerulus, lowering glomerular BP and GFR

What percentage of the filtrate is reabsorbed in the proximal convoluted tubule (PCT)?
A) 25%
B) 50%
C) 65%
D) 80%

C) 65%

Where does the reabsorbed filtrate from the PCT go?
A) Vasa recta
B) Collecting duct
C) Peritubular capillaries
D) Renal pelvis

C) Peritubular capillaries

What drives the reabsorption of other solutes and water in the PCT?
A) Osmosis alone
B) Passive diffusion of urea
C) Cotransport and active transport of Na⁺
D) Filtration slits

C) Cotransport and active transport of Na⁺

Approximately how much of the body’s resting ATP is used for active transport in the PCT?
A) 2%
B) 4%
C) 6%
D) 10%

C) 6%

What percentage of the filtrate is reabsorbed in the nephron loop?
A) 10%
B) 25%
C) 50%
D) 65%

B) 25%

Where is the reabsorbed filtrate from the nephron loop sent?
A) Peritubular capillaries
B) Vasa recta
C) Glomerulus
D) Renal pelvis

B) Vasa recta

What is reabsorbed in the distal convoluted tubule (DCT) under hormonal control?
A) Glucose and amino acids
B) Water, Na⁺, and Cl⁻
C) Calcium and phosphate
D) Protein and urea

B) Water, Na⁺, and Cl⁻

Where does the reabsorbed filtrate from the DCT go?
A) Renal corpuscle
B) Ureter
C) Peritubular capillaries
D) Loop of Henle

C) Peritubular capillaries

What is the filtrate considered once it exits the DCT?
A) Filtrate
B) Plasma
C) Lymph
D) Urine

D) Urine

What happens in the collecting duct during the final stage of reabsorption?
A) Filtrate is filtered again
B) Hormones are secreted
C) Water is conserved, concentrating the urine
D) Electrolytes are removed

C) Water is conserved, concentrating the urine

What is the process of tubular secretion?
A) Reabsorbing water into the bloodstream
B) Filtering blood at the glomerulus
C) Removing additional substances from the blood and adding them to the filtrate
D) Moving urine to the bladder

C) Removing additional substances from the blood and adding them to the filtrate

Where does most tubular secretion occur in the nephron?
A) Glomerulus and PCT
B) Loop of Henle and renal pelvis
C) Distal convoluted tubule (DCT) and collecting duct
D) Bowman’s capsule

C) Distal convoluted tubule (DCT) and collecting duct

How are substances transported into the filtrate during tubular secretion?
A) By osmosis only
B) Through capillary rupture
C) By active transport and diffusion
D) By gravity and hydrostatic pressure

C) By active transport and diffusion

What is the effect of H⁺ (hydrogen ion) secretion during tubular secretion?
A) It raises the pH of blood (makes it less acidic)
B) It lowers the pH of blood
C) It increases blood glucose
D) It blocks water reabsorption

A) It raises the pH of blood (makes it less acidic)

What is the result of secreting bicarbonate ions (HCO₃⁻) into the filtrate?
A) Raises blood pressure
B) Lowers blood pH (makes it more acidic)
C) Enhances nutrient absorption
D) Increases oxygen saturation

B) Lowers blood pH (makes it more acidic)

Tubular secretion plays an important role in removing which of the following from the blood?
A) Red blood cells and platelets
B) Hormones and glucose
C) Nitrogenous wastes and bile acids
D) Oxygen and carbon dioxide

C) Nitrogenous wastes and bile acids

How does tubular secretion contribute to detoxification?
A) It dilutes drugs in the urine
B) It reabsorbs medications for reuse
C) It helps clear drugs and environmental contaminants from the blood
D) It traps drugs in the renal pelvis

C) It helps clear drugs and environmental contaminants from the blood

What is the role of the nephron loop in water conservation?
A) It filters blood cells from plasma
B) It generates the high osmolarity (salinity) of the medullary extracellular fluid
C) It secretes excess sodium into the urine
D) It stores concentrated urine for excretion

B) It generates the high osmolarity (salinity) of the medullary extracellular fluid

What does high osmolarity or salinity in the kidney medulla mean?
A) Low solute concentration
B) No urea present
C) High solute concentration
D) High blood pressure

C) High solute concentration

How does salinity change as you move deeper into the renal medulla?
A) It decreases
B) It stays constant
C) It increases
D) It fluctuates randomly

C) It increases

Where in the nephron does urine concentration primarily occur through water conservation?
A) Renal corpuscle
B) Proximal convoluted tubule
C) Nephron loop
D) Collecting duct

D) Collecting duct

How is water reabsorbed in the collecting duct during water conservation?
A) By active transport
B) Through secretion of hormones
C) By osmosis due to high medullary osmolarity
D) By capillary hydrostatic pressure

C) By osmosis due to high medullary osmolarity

What is water conservation in the context of kidney function?
A) Prevention of water entering the filtrate
B) Storage of excess water in the bladder
C) Reabsorption of water from the collecting duct back into the bloodstream
D) Conversion of water to salt

C) Reabsorption of water from the collecting duct back into the bloodstream

What is the primary function of the nephron loop (Loop of Henle)?
A) To reabsorb glucose
B) To filter blood
C) To generate the high salinity of the medulla’s extracellular fluid
D) To store urine before excretion

C) To generate the high salinity of the medulla’s extracellular fluid

From which part of the nephron does the nephron loop receive filtrate?
A) Collecting duct
B) Glomerulus
C) Distal convoluted tubule
D) Proximal convoluted tubule

D) Proximal convoluted tubule

What describes the descending limb of the nephron loop?
A) Ascends toward the cortex; permeable to salts
B) Descends into the medulla; thin segment permeable to water but not salts
C) Is thick and impermeable to both water and salts
D) Connects directly to the ureter

B) Descends into the medulla; thin segment permeable to water but not salts

What describes the ascending limb of the nephron loop?
A) Permeable to water only
B) Thin and permeable to both water and salt
C) Thick segment is impermeable to water but permeable to salts
D) Secretes nitrogenous wastes into the filtrate

C) Thick segment is impermeable to water but permeable to salts

Where does the filtrate go after passing through the nephron loop?
A) Glomerulus
B) Collecting duct
C) Distal convoluted tubule
D) Bowman’s capsule

C) Distal convoluted tubule

Why is the nephron loop described as a countercurrent multiplier?
A) It filters red blood cells
B) It stores urine in the renal medulla
C) It uses opposing fluid flow and salt reabsorption to create a salinity gradient
D) It actively pumps water into the collecting duct

C) It uses opposing fluid flow and salt reabsorption to create a salinity gradient

What does the "multiplier" refer to in the term "countercurrent multiplier"?
A) The multiplication of glomeruli in the nephron
B) The increase in water reabsorption
C) The intensification of salinity/osmolarity in the medulla's extracellular fluid
D) The duplication of nephron loops

C) The intensification of salinity/osmolarity in the medulla's extracellular fluid

How is salt added to the medullary extracellular fluid to increase osmolarity?
A) Through secretion from the collecting duct
B) By reabsorption from the nephron loop (ascending limb)
C) By filtration at the glomerulus
D) Through active transport by the DCT

B) By reabsorption from the nephron loop (ascending limb)

What does the term "countercurrent" refer to in the nephron loop?
A) Blood moving in the same direction as filtrate
B) Water moving into the nephron
C) Fluid moving in opposite directions in the ascending and descending limbs
D) Active salt secretion into both limbs

C) Fluid moving in opposite directions in the ascending and descending limbs

What is the permeability characteristic of the descending limb of the nephron loop?
A) Permeable to both water and salts
B) Impermeable to both water and salts
C) Permeable to salts but not water
D) Permeable to water, not salts

D) Permeable to water, not salts

As filtrate moves down the descending limb, what environmental change does it encounter?
A) Decreasing temperature
B) Decreasing pH
C) Increasing osmolarity of the surrounding medullary fluid
D) Increasing blood pressure

C) Increasing osmolarity of the surrounding medullary fluid

What happens to filtrate as water leaves it in the descending limb?
A) It becomes more dilute
B) It freezes
C) It becomes more concentrated
D) It evaporates

C) It becomes more concentrated

What is the approximate osmolarity of the filtrate at the bottom of the nephron loop?
A) 100 mOsm/L
B) 300 mOsm/L
C) 600 mOsm/L
D) 1200 mOsm/L

D) 1200 mOsm/L

Does urine concentration occur in the descending limb?
A) Yes, urine is concentrated here
B) No, urine concentration occurs later in the collecting duct
C) Yes, due to salt pumping
D) No, this is where filtrate is diluted

No, urine concentration occurs later in the collecting duct

What is the ascending limb of the nephron loop permeable to?
A) Water only
B) Urea and glucose
C) Salts like Na⁺, K⁺, and Cl⁻ but not water
D) Plasma proteins

C) Salts like Na⁺, K⁺, and Cl⁻ but not water

How are Na⁺, K⁺, and Cl⁻ transported from the ascending limb into the extracellular fluid?
A) Osmosis
B) Passive diffusion
C) Active transport
D) Filtration

C) Active transport

Why does the medulla develop high osmolarity?
A) More salt is pumped out of the ascending limb than water is lost from the descending limb
B) Urea builds up in the cortex
C) The DCT stores salt
D) Water enters the nephron at the loop

A) More salt is pumped out of the ascending limb than water is lost from the descending limb

What is the condition of the filtrate when it enters the distal convoluted tubule (DCT)?
A) More concentrated than before
B) Same as plasma
C) More dilute than it was in the proximal convoluted tubule (PCT)
D) Containing only urea

C) More dilute than it was in the proximal convoluted tubule (PCT)

What is the vasa recta?
A) A section of the nephron loop
B) Capillaries located in the renal cortex
C) Capillaries located in the medulla that parallel the nephron loop
D) Lymphatic vessels draining the kidney

C) Capillaries located in the medulla that parallel the nephron loop

What is the primary function of the vasa recta in relation to the nephron loop?
A) Filter plasma at the glomerulus
B) Secrete hormones into the nephron
C) Reabsorb water and solutes from the nephron loop
D) Concentrate urine directly

C) Reabsorb water and solutes from the nephron loop

How does the vasa recta affect the osmolarity of the medulla?
A) It increases osmolarity by retaining more salt
B) It decreases osmolarity by absorbing all the water
C) It does not contribute to or subtract from medullary osmolarity
D) It dilutes the medulla through active secretion

C) It does not contribute to or subtract from medullary osmolarity

What balance does the vasa recta maintain to preserve medullary osmolarity?
A) Reabsorbs only water
B) Reabsorbs only salt
C) Reabsorbs equal amounts of water and salt
D) Does not reabsorb anything

C) Reabsorbs equal amounts of water and salt

What occurs in the descending portion of the vasa recta?
A) NaCl diffuses out of blood and water diffuses in
B) NaCl diffuses into blood; water diffuses out
C) Glucose is reabsorbed
D) No exchange occurs

B) NaCl diffuses into blood; water diffuses out

What occurs in the ascending portion of the vasa recta?
A) NaCl diffuses into blood and water diffuses out
B) Both NaCl and water diffuse out
C) NaCl diffuses out of blood; water diffuses in
D) Only oxygen is exchanged

C) NaCl diffuses out of blood; water diffuses in

From which part of the nephron does the collecting duct receive urine?
A) Proximal convoluted tubule
B) Nephron loop
C) Glomerulus
D) Distal convoluted tubule

D) Distal convoluted tubule

In which direction does the collecting duct carry urine?
A) From the medulla to the cortex
B) From the ureter to the glomerulus
C) From the cortex to the medulla
D) From the renal pelvis to the nephron

C) From the cortex to the medulla