Which pigment gives normal urine its yellow color?
Urochrome
✓
Melanin
Hemoglobin
Biliverdin
Correct Answer
Urochrome
Urochrome is a yellow pigment that forms from the breakdown of hemoglobin and is excreted by the kidneys. Melanin is the brown pigment of skin and hair and is not a normal urine pigment. Hemoglobin in urine is abnormal and gives a red or brown tint. Biliverdin is a green bile pigment, not the source of urine's yellow color.
Category: Urine and Its Transport
Question 2
Which tube carries urine from each kidney to the urinary bladder?
Urethra
Ureter
✓
Renal vein
Collecting duct
Correct Answer
Ureter
Each kidney drains into its own ureter, a muscular tube that runs down to the posterior bladder wall. The urethra carries urine from the bladder to the outside of the body. The renal vein carries blood, not urine, away from the kidney. A collecting duct is a microscopic tubule inside the kidney that drains into the calyces.
Category: Urine and Its Transport
Question 3
Which muscle contracts to push urine out of the bladder during urination?
Levator ani muscle
Internal urethral sphincter
Detrusor muscle
✓
External urethral sphincter
Correct Answer
Detrusor muscle
The detrusor muscle is the smooth muscle of the bladder wall, and its contraction expels urine during micturition. Levator ani muscle forms much of the pelvic floor and relaxes during urination. Internal urethral sphincter is smooth muscle at the bladder neck that relaxes to let urine pass. External urethral sphincter is skeletal muscle that relaxes under voluntary control during urination.
Category: Urine and Its Transport
Question 4
Which sphincter, made of skeletal muscle, gives a person voluntary control over urination?
Internal urethral sphincter
Pyloric sphincter
Precapillary sphincter
External urethral sphincter
✓
Correct Answer
External urethral sphincter
The external urethral sphincter is skeletal muscle of the pelvic floor, so it is under conscious control. Internal urethral sphincter is smooth muscle at the bladder neck and is involuntary. Pyloric sphincter controls the passage of chyme from the stomach to the duodenum. Precapillary sphincter regulates blood flow into capillary beds.
Category: Urine and Its Transport
Question 5
The cone-shaped renal pyramids make up which region of the kidney?
Renal medulla
✓
Renal cortex
Renal pelvis
Renal capsule
Correct Answer
Renal medulla
The renal medulla is the inner region of the kidney, made up of the renal pyramids. Renal cortex is the outer granular layer that contains the renal corpuscles. Renal pelvis is the funnel-shaped cavity that collects urine from the calyces. Renal capsule is the fibrous connective tissue covering the outside of the kidney.
Category: Kidney Anatomy
Question 6
Blood vessels, nerves and the urine outflow tube pass into or out of the kidney through which indented region on its medial border?
Renal papilla
Renal hilum
✓
Renal cortex
Renal column
Correct Answer
Renal hilum
The renal hilum is the notch on the concave medial border where the renal artery, renal vein, nerves and ureter connect to the kidney. Renal papilla is the tip of a renal pyramid that drains into a minor calyx. Renal cortex is the outer layer of the kidney. Renal column is cortical tissue that extends between pyramids.
Category: Kidney Anatomy
Question 7
Which vessel delivers blood directly into the glomerulus?
Efferent arteriole
Arcuate vein
Afferent arteriole
✓
Peritubular capillary
Correct Answer
Afferent arteriole
The afferent arteriole carries blood into the glomerular capillaries for filtration. Efferent arteriole carries blood out of the glomerulus. Arcuate vein returns blood from the kidney toward the renal vein. Peritubular capillary receives blood from the efferent arteriole after filtration has already happened.
Category: Nephron Structure
Question 8
Which cells of the visceral layer of the glomerular capsule wrap around the glomerular capillaries with foot processes?
Mesangial cells
Juxtaglomerular cells
Intercalated cells
Podocytes
✓
Correct Answer
Podocytes
Podocytes extend foot processes that interlock around the glomerular capillaries, leaving filtration slits between them. Mesangial cells sit between the glomerular capillaries and support them. Juxtaglomerular cells are modified smooth muscle cells in the afferent arteriole wall. Intercalated cells are found in the collecting duct and help regulate pH.
Category: Nephron Structure
Question 9
Which long, straight capillaries run alongside the nephron loops of juxtamedullary nephrons deep into the medulla?
Vasa recta
✓
Interlobar veins
Glomerular capillaries
Arcuate arteries
Correct Answer
Vasa recta
The vasa recta arise from the efferent arterioles of juxtamedullary nephrons and parallel their long nephron loops in the medulla. Interlobar veins are larger vessels that run between renal pyramids. Glomerular capillaries form the filtering tuft inside the renal corpuscle. Arcuate arteries arch along the border between the cortex and medulla.
Category: Nephron Structure
Question 10
Which segment of the renal tubule reabsorbs the largest share of the filtered water and sodium?
Distal convoluted tubule
Proximal convoluted tubule
✓
Collecting duct
Nephron loop
Correct Answer
Proximal convoluted tubule
The proximal convoluted tubule reabsorbs most of the filtered water and sodium, along with nearly all filtered glucose and amino acids. Distal convoluted tubule reabsorbs a much smaller amount under hormonal control. Collecting duct makes the final, hormone-regulated adjustments to water reabsorption. Nephron loop reabsorbs a moderate share and builds the medullary gradient.
Category: Tubular Reabsorption
Question 11
In uncontrolled diabetes mellitus, glucose appears in the urine because the filtered glucose exceeds the renal tubule's
Filtration fraction
Osmotic gradient
Transport maximum
✓
Hydrostatic pressure
Correct Answer
Transport maximum
The transport maximum is the highest rate at which carrier proteins can reabsorb a substance, and filtered glucose above that rate stays in the urine. Filtration fraction is the share of plasma that is filtered at the glomerulus. Osmotic gradient describes differences in solute concentration that drive water movement. Hydrostatic pressure is a fluid pressure that drives filtration, not a limit on carrier transport.
Category: Tubular Reabsorption
Question 12
Which part of the nephron loop actively transports sodium and chloride out of the filtrate while remaining impermeable to water?
Thin descending limb
Collecting duct
Renal corpuscle
Thick ascending limb
✓
Correct Answer
Thick ascending limb
The thick ascending limb pumps sodium and chloride into the medullary interstitium but does not let water follow, so the filtrate becomes more dilute. Thin descending limb is permeable to water and loses water to the salty medulla. Collecting duct is not part of the nephron loop and its water permeability depends on ADH. Renal corpuscle is the filtering unit, not a segment of the loop.
Category: Tubular Reabsorption
Question 13
Which process in the nephron loops of juxtamedullary nephrons builds the high solute concentration of the medullary interstitial fluid?
Countercurrent multiplier
✓
Myogenic mechanism
Tubuloglomerular feedback
Glomerular filtration
Correct Answer
Countercurrent multiplier
The countercurrent multiplier uses fluid flowing in opposite directions in the two limbs of the loop, with salt pumped out of the ascending limb, to build a steep medullary gradient. Myogenic mechanism is an autoregulation response of the afferent arteriole to stretch. Tubuloglomerular feedback adjusts GFR based on the salt content of distal tubular fluid. Glomerular filtration forms the filtrate but does not concentrate the medulla.
Category: Tubular Reabsorption
Question 14
Which pressure is the main force pushing fluid out of the glomerular capillaries into the capsular space?
Blood colloid osmotic pressure
Glomerular blood hydrostatic pressure
✓
Capsular hydrostatic pressure
Interstitial fluid osmotic pressure
Correct Answer
Glomerular blood hydrostatic pressure
Glomerular blood hydrostatic pressure is the blood pressure in the glomerular capillaries, and it is the main force driving filtration. Blood colloid osmotic pressure, created by plasma proteins, opposes filtration. Capsular hydrostatic pressure, from fluid already in the capsule, also opposes filtration. Interstitial fluid osmotic pressure is not one of the main forces acting across the glomerular membrane.
Category: Filtration and Blood Flow
Question 15
When rising blood pressure stretches the arteriole that feeds a glomerulus, its smooth muscle contracts to limit blood flow into the glomerulus. This autoregulation response is the
Renin-angiotensin system
Countercurrent exchanger
Myogenic mechanism
✓
Tubuloglomerular feedback
Correct Answer
Myogenic mechanism
The myogenic mechanism is the built-in tendency of vascular smooth muscle to contract when stretched, which keeps glomerular filtration steady. Renin-angiotensin system is a hormonal pathway, not a direct stretch response. Countercurrent exchanger describes the vasa recta preserving the medullary gradient. Tubuloglomerular feedback relies on the macula densa sensing salt in the tubular fluid, not on stretch of the arteriole.
Category: Filtration and Blood Flow
Question 16
In tubuloglomerular feedback, which cells in the wall of the distal tubule sense the sodium chloride level of the tubular fluid?
Principal cells
Mesangial cells
Podocytes
Macula densa cells
✓
Correct Answer
Macula densa cells
Macula densa cells are tall, crowded cells of the distal tubule where it touches the afferent arteriole, and they monitor the salt content of the passing fluid. Principal cells of the collecting duct respond to ADH and aldosterone. Mesangial cells support the glomerular capillaries. Podocytes wrap the glomerular capillaries and form the filtration slits.
Category: Filtration and Blood Flow
Question 17
Antidiuretic hormone increases water reabsorption by causing collecting duct cells to insert which channels into their membranes?
Aquaporins
✓
Calcium channels
Chloride channels
Gap junctions
Correct Answer
Aquaporins
Aquaporins are water channel proteins, and ADH causes collecting duct cells to insert more of them so water can leave the filtrate by osmosis. Calcium channels let calcium ions cross membranes and do not carry water. Chloride channels move chloride ions. Gap junctions connect the cytoplasm of neighboring cells and are not how ADH acts.
Category: Hormonal Regulation
Question 18
Which adrenal cortex hormone increases sodium reabsorption and potassium secretion in the distal tubule and collecting duct?
Atrial natriuretic peptide
Aldosterone
✓
Parathyroid hormone
Calcitonin
Correct Answer
Aldosterone
Aldosterone acts on the distal tubule and collecting duct to reabsorb sodium and secrete potassium, and water tends to follow the sodium. Atrial natriuretic peptide does the opposite and increases sodium loss in urine. Parathyroid hormone mainly increases calcium reabsorption. Calcitonin lowers blood calcium and has no major role in sodium handling.
Category: Hormonal Regulation
Question 19
In response to low blood oxygen, the kidneys secrete which hormone that stimulates red blood cell production?
Renin
Calcitriol
Erythropoietin
✓
Thrombopoietin
Correct Answer
Erythropoietin
Erythropoietin is released by the kidneys when tissue oxygen falls and it stimulates the red bone marrow to make more red blood cells. Renin is an enzyme the kidneys release when blood pressure falls. Calcitriol is the active form of vitamin D and controls calcium absorption. Thrombopoietin stimulates platelet production and is made mainly by the liver.
Category: Hormonal Regulation
Question 20
Which collecting duct cells secrete hydrogen ions or bicarbonate to help regulate acid-base balance?
Principal cells
Podocytes
Juxtaglomerular cells
Intercalated cells
✓
Correct Answer
Intercalated cells
Intercalated cells of the collecting duct secrete hydrogen ions or bicarbonate as needed, which helps keep blood pH in range. Principal cells mainly handle water and sodium under the control of ADH and aldosterone. Podocytes are filtration cells around the glomerulus. Juxtaglomerular cells secrete renin.
Category: Acid-Base Balance