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Comprehensive MCAT Checklist - Excretory System

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1. What are the two main functions of the kidneys?

A. Retain nutrients and remove waste
B. Produce hormones and regulate temperature
C. Store urine and filter oxygen
D. Control heart rate and blood pressure

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2. What is the primary function of the vasa recta?

A. Filter blood and remove waste
B. Supply oxygen to kidney tissue
C. Produce urine directly
D. Store nutrients for the body

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3. What is the function of peritubular capillaries?

A. Recollect nutrients that kidneys filter to prevent loss in urine
B. Supply oxygen to kidney tissue
C. Filter waste products from blood
D. Store urine before elimination

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4. 4. What is the correct route of blood through the kidney?

A. Renal vein → kidney filtration → renal artery
B. Renal artery → kidney filtration → renal vein
C. Ureter → kidney filtration → renal pelvis
D. Renal pelvis → kidney filtration → ureter

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5. A patient with diabetic nephropathy shows protein in their urine, indicating damage to the filtration barrier. Which component of the renal corpuscle is most likely compromised?

A. The collecting duct's ability to concentrate urine
B. The proximal tubule's reabsorption capacity
C. The glomerular filtration barrier between the glomerulus and Bowman's capsule
D. The loop of Henle's countercurrent multiplier system

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6. What is the primary function of the proximal convoluted tubule (PCT)?

A. Reabsorb nutrients, water, and electrolytes while secreting waste products
B. Concentrate urine through water reabsorption only
C. Filter blood to form initial filtrate
D. Store urine before elimination

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7. A defect in the descending limb of the loop of Henle would most likely lead to which consequence?

A. concentrate urine
B. dilute urine
C. filter blood
D. store urine

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8. The ascending loop of Henle is impermeable to water. What is the significance of this property?

A. It reabsorbs sodium and chloride ions while allowing water to remain in the filtrate
B. It reabsorbs water while allowing sodium and chloride ions to remain in the filtrate
C. It allows for the passive diffusion of water and solutes
D. It is impermeable to all solutes and water

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9. Blood flow regulation in the glomerulus involves two arterioles with different functions. If the afferent arteriole constricts while the efferent arteriole remains unchanged, what would be the expected effect on glomerular filtration rate?

A. Glomerular filtration rate would increase due to higher pressure in the glomerulus
B. Glomerular filtration rate would decrease due to reduced blood flow into the glomerulus
C. Glomerular filtration rate would remain unchanged since only one arteriole is affected
D. Glomerular filtration rate would increase due to backup of blood in the efferent arteriole

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10. What do the renal calyces do?

A. Collect urine from the nephrons
B. Filter blood to make urine
C. Store urine before elimination
D. Transport urine to the bladder

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11. The renal pelvis is formed when multiple renal calyces merge together. What is the primary function of this anatomical arrangement?

A. To increase the surface area for additional urine filtration
B. To provide structural support for the kidney tissue
C. To funnel collected urine from multiple calyces into a single exit point leading to the ureter
D. To regulate the concentration of urine before it leaves the kidney

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12. Which area of the kidney would most likely contain least volume of urine?

A. A renal calyx
B. Multiple renal calyces
C. Renal cortex
D. Ureter

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13. A patient with chronic hypertension develops glomerulosclerosis, where the glomerular capillaries become hardened and less permeable. How would this pathological change most directly affect the initial step of urine formation?

A. Increased filtration due to higher resistance in hardened capillaries
B. Decreased glomerular filtration due to reduced capillary permeability despite maintained blood pressure
C. Normal filtration since blood pressure remains the primary driving force
D. Enhanced selectivity of filtration leading to improved kidney function

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14. During glomerular filtration, a deficient basement membrane would most likely lead to which of the following?

A. Increased proteinuria due to larger molecules passing through the filtration barrier
B. Decreased glomerular filtration rate due to thickening of the filtration barrier
C. Enhanced reabsorption of nutrients in the proximal tubule
D. Reduced urine concentration ability in the loop of Henle

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15. During glomerular filtration, the filtration barrier consists of three layers that determine what substances can pass from blood into Bowman's capsule. A researcher studying this barrier finds that larger molecules are completely blocked while smaller molecules pass through freely. This size-selective filtration is primarily determined by which component of the renal corpuscle?

A. The fenestrated endothelium of glomerular capillaries
B. The podocyte foot processes surrounding the capillaries
C. The basement membrane of the glomerular capillaries acting as a molecular sieve
D. The mesangial cells within the glomerular tuft

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16. Which of the following would you least expect to be filtrated by the endothelium?

A. Water
B. Glucose
C. Sodium ions
D. Erythrocytes

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17. What is the difference between intrinsic and extrinsic regulation of kidney function?

A. Intrinsic regulation is self-regulation by the kidneys, extrinsic regulation involves nervous and hormonal control
B. Intrinsic regulation uses hormones, extrinsic regulation uses blood pressure
C. Intrinsic regulation controls blood flow, extrinsic regulation controls urine production
D. Both types of regulation work the same way

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18. What components are typically found in the filtrate formed at the glomerulus?

A. Water and small ions
B. Water, ions, glucose, and amino acids, but not red blood cells or large proteins
C. Blood components including red blood cells and proteins
D. Only waste products and toxins

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19. In the distal convoluted tubule, calcium and additional sodium are reabsorbed. If a person has low dietary calcium intake, what would you expect to happen in this region?

A. Increased calcium reabsorption to maintain blood calcium levels
B. Decreased calcium reabsorption to conserve energy
C. No change in calcium reabsorption
D. Calcium secretion into the urine

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20. Multiple nephrons empty into a single collecting duct that travels through the salty medulla. What advantage does this arrangement provide for water conservation?

A. More nephrons means more filtration capacity
B. The collecting duct can reabsorb more water when it passes through the concentrated salt environment of the medulla
C. Multiple nephrons reduce the workload on each individual nephron
D. The arrangement allows for faster urine production

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21. Anti-diuretic hormone (ADH) makes the collecting duct more permeable to water. During dehydration, when ADH levels are high, what would happen to urine concentration?

A. Urine becomes more dilute as water is retained in the duct
B. Urine concentration stays the same regardless of ADH levels
C. Urine becomes more concentrated as more water is reabsorbed back into the bloodstream
D. No urine is produced when ADH levels are high

____________________________________________________________________________ 22. In the proximal convoluted tubule, glucose reabsorption occurs through a two-step process. Glucose enters the cell from the filtrate via a sodium-glucose symporter on the apical membrane, then exits the cell into the bloodstream via a glucose transporter on the basolateral membrane. If the sodium-potassium pump on the basolateral membrane were inhibited, what would be the expected effect on glucose reabsorption?

A. Glucose reabsorption would increase due to higher intracellular sodium concentrations
B. Glucose reabsorption would remain unchanged since the basolateral glucose transporter doesn't require sodium
C. Glucose reabsorption would decrease because the sodium gradient needed for the apical symporter would be lost
D. Only the exit of glucose from the cell would be affected, not its entry from the filtrate

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23. The proximal convoluted tubule primarily participates in:

A. Reabsorption of nutrients, ions, and water from the filtrate
B. Concentration of urine through water reabsorption
C. Filtration of blood to form initial filtrate
D. Storage of urine before elimination

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24. The sodium-glucose symporter in the proximal tubule uses the sodium gradient to transport glucose against its concentration gradient by secondary active transport into the cell then into the bloodstream. For this to be classified as secondary active transport, which of the following must be true?

A. The pump directly used ATP to move glucose
B. The pump did not directly use ATP
C. The pump moved glucose down its concentration gradient
D. The pump moved sodium against its concentration gradient

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25. In the ascending limb of the Loop of Henle, the sodium-potassium pump creates a gradient that powers a sodium-potassium-chloride symporter. What is the main purpose of removing salts from the filtrate in this region?

A. To make the surrounding medulla salty so the descending limb can reabsorb water
B. To directly produce concentrated urine in the ascending limb
C. To filter out waste products from the blood
D. To store salts for later use by the body

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26. Which of the following would least likely to occur in the descending limb of the Loop of Henle?

A. Active reabsorption of water
B. The medulla becomes increasingly salty
C. Interstitial fluid becomes increasingly concentrated
D. Passive diffusion of water

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27. After filtrate passes through the loop of Henle, it enters the distal convoluted tubule and then the collecting duct. What is the primary difference between these two structures in terms of urine processing?

A. The distal convoluted tubule filters blood while the collecting duct stores urine
B. The distal convoluted tubule primarily reabsorbs ions like sodium and chloride, while the collecting duct focuses on water reabsorption and final urine concentration
C. The distal convoluted tubule concentrates urine while the collecting duct dilutes it
D. Both structures perform identical functions in urine processing

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28. The distal convoluted tubule passes close to the glomerulus, forming part of the juxtaglomerular apparatus. If blood pressure drops significantly, specialized cells in this apparatus would most likely respond by:

A. Decreasing sodium reabsorption in the distal convoluted tubule to reduce blood volume
B. Increasing water secretion to lower blood pressure further
C. An increase in sodium reabsorption in the distal convoluted tubule and constricts blood vessels
D. Dilating the afferent arteriole to reduce glomerular filtration pressure

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29. What is the key difference between the internal and external urethral sphincters in terms of muscle type and control?

A. The internal sphincter is made of skeletal muscle and is voluntarily controlled, while the external sphincter is made of smooth muscle and is involuntarily controlled
B. The internal sphincter is made of smooth muscle and is involuntarily controlled, while the external sphincter is made of skeletal muscle and is voluntarily controlled
C. Both sphincters are made of smooth muscle and are involuntarily controlled
D. Both sphincters are made of skeletal muscle and are voluntarily controlled

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30. The counter-current multiplier mechanism in the loop of Henle creates a concentration gradient in the medulla that is essential for urine concentration. Which of the following best describes how this mechanism works?

A. Both limbs of the loop actively transport water in opposite directions to create the concentration gradient
B. The descending limb actively pumps out solutes while the ascending limb reabsorbs water
C. The ascending limb actively transports NaCl out while being impermeable to water, creating high osmolarity in the medulla that drives water reabsorption from the permeable descending limb
D. The collecting duct creates the gradient by varying its permeability to different solutes