Kidney Structure and Function Practice Questions
20 free Kidney Structure and Function practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following describes the correct order of blood flow through the renal vasculature?
- A Interlobar artery, Arcuate artery, Interlobular artery, Afferent arteriole
- B Arcuate artery, Interlobar artery, Afferent arteriole, Interlobular artery
- C Interlobular artery, Arcuate artery, Afferent arteriole, Efferent arteriole
- D Afferent arteriole, Glomerulus, Interlobular artery, Efferent arteriole
Correct answer: Interlobar artery, Arcuate artery, Interlobular artery, Afferent arteriole
Blood enters the kidney via the renal artery and branches into interlobar arteries, which then arch over the pyramids as arcuate arteries. From there, interlobular (cortical radiate) arteries extend into the cortex to supply the afferent arterioles.
The functional unit of the kidney, the nephron, consists of two main components. These are the:
- A Renal corpuscle and renal tubule
- B Glomerulus and Bowman's capsule
- C Cortex and medulla
- D Afferent and efferent arterioles
Correct answer: Renal corpuscle and renal tubule
The renal corpuscle is the site of blood filtration, while the renal tubule is responsible for reabsorption and secretion. Together, these structures perform the essential functions of the nephron.
Which cell type in the filtration barrier possesses foot processes (pedicels) that form filtration slits?
- A Fenestrated endothelial cells
- B Mesangium
- C Macula densa cells
- D Podocytes
Correct answer: Podocytes
Podocytes are specialized visceral epithelial cells of Bowman's capsule that wrap around glomerular capillaries. The gaps between their interdigitating pedicels are called filtration slits, which help regulate the passage of macromolecules.
What is the primary physiological function of the Juxtaglomerular (JG) cells?
- A Sensing sodium concentration in the distal tubule
- B Secreting renin in response to low blood pressure
- C Phagocytosis of trapped macromolecules in the basement membrane
- D Filtering glucose out of the plasma
Correct answer: Secreting renin in response to low blood pressure
JG cells are modified smooth muscle cells in the wall of the afferent arteriole that act as baroreceptors. They synthesize and release renin to activate the Renin-Angiotensin-Aldosterone System when systemic blood pressure drops.
In a healthy individual, which of the following substances is virtually 100% reabsorbed in the proximal convoluted tubule?
- A Urea
- B Creatinine
- C Glucose
- D Sodium
Correct answer: Glucose
Under normal physiological conditions, all filtered glucose is reabsorbed in the proximal tubule via secondary active transport with sodium. Glucose only appears in the urine if blood levels exceed the renal threshold (approximately 180 mg/dL).
The myogenic mechanism of renal autoregulation involves which of the following responses to an increase in arterial blood pressure?
- A Dilation of the afferent arteriole
- B Constriction of the afferent arteriole
- C Constriction of the efferent arteriole
- D Release of nitric oxide by endothelial cells
Correct answer: Constriction of the afferent arteriole
The myogenic mechanism is an intrinsic property of vascular smooth muscle that responds to stretch. Increased pressure stretches the afferent arteriole, causing it to constrict to keep glomerular filtration rate (GFR) constant.
Which portion of the Loop of Henle is highly permeable to water but nearly impermeable to solutes like sodium and chloride?
- A Thin ascending limb
- B Thick ascending limb
- C Thin descending limb
- D Distal convoluted tubule
Correct answer: Thin descending limb
The descending limb of the Loop of Henle allows water to leave the tubule osmotically into the hypertonic medullary interstitium. Because it lacks significant solute transporters, the tubular fluid becomes increasingly concentrated as it descends.
The primary driving force for glomerular filtration is:
- A Colloid osmotic pressure of the plasma
- B Hydrostatic pressure within Bowman's capsule
- C Glomerular capillary hydrostatic pressure
- D Active transport by the podocytes
Correct answer: Glomerular capillary hydrostatic pressure
Glomerular filtration is driven by Starling forces, specifically the high hydrostatic pressure in the glomerular capillaries. This pressure overcomes the opposing forces of plasma oncotic pressure and Bowman's capsule hydrostatic pressure.
Which part of the nephron is the primary site for the action of Parathyroid Hormone (PTH) to increase calcium reabsorption?
- A Proximal convoluted tubule
- B Descending limb of Loop of Henle
- C Distal convoluted tubule
- D Collecting duct
Correct answer: Distal convoluted tubule
While calcium is reabsorbed throughout the nephron, PTH specifically targets the distal convoluted tubule to increase the expression of calcium channels. This allows for fine-tuning of calcium excretion based on the body's needs.
The 'Countercurrent Multiplier' system, essential for concentrating urine, is primarily established by the activity of the:
- A Proximal tubule
- B Loop of Henle
- C Vasa recta
- D Glomerulus
Correct answer: Loop of Henle
The Loop of Henle acts as a multiplier by actively pumping salts out of the thick ascending limb, creating an osmotic gradient in the medulla. This gradient is then used by the collecting ducts to reabsorb water.
Which substance is commonly used to estimate GFR because it is freely filtered but neither reabsorbed nor significantly secreted by the tubules?
- A Serum albumin
- B Inulin (a fructose polymer)
- C Blood glucose
- D Para-aminohippuric acid (PAH)
Correct answer: Inulin (a fructose polymer)
Inulin is the gold standard for measuring GFR because its clearance rate equals the filtration rate. Creatinine is used more commonly in clinical practice, though it is slightly secreted by the tubules.
Macula densa cells are located in the wall of the distal tubule and function to sense changes in:
- A Blood pressure in the afferent arteriole
- B NaCl concentration in the tubular fluid
- C Oxygen tension in the renal medulla
- D Plasma oncotic pressure
Correct answer: NaCl concentration in the tubular fluid
As part of tubuloglomerular feedback, macula densa cells detect the delivery of NaCl. If NaCl concentration is too high, they signal the afferent arteriole to constrict, thereby reducing GFR and slowing flow.
The majority of the kidney's energy consumption is used to power which of the following processes?
- A Glomerular filtration
- B Active reabsorption of sodium
- C Secretion of creatinine
- D Synthesis of erythropoietin hormone
Correct answer: Active reabsorption of sodium
The kidneys have a very high metabolic rate because they must actively transport massive amounts of sodium back into the blood. This is primarily driven by the Na+/K+ ATPase pump located on the basolateral membranes of tubular cells.
Which hormone acts on the principal cells of the collecting duct to increase water permeability by inserting aquaporin-2 channels?
- A Aldosterone
- B Atrial Natriuretic Peptide (ANP)
- C Antidiuretic Hormone (ADH)
- D Angiotensin II
Correct answer: Antidiuretic Hormone (ADH)
ADH (vasopressin) binds to V2 receptors on the collecting duct cells. This triggers a signaling cascade that moves vesicles containing aquaporin-2 to the apical membrane, allowing for facultative water reabsorption.
What happens to the Glomerular Filtration Rate (GFR) if the efferent arteriole is constricted while the afferent arteriole remains unchanged?
- A GFR decreases
- B GFR remains constant
- C Filtration stops entirely
- D GFR increases
Correct answer: GFR increases
Constricting the efferent arteriole creates 'back pressure' in the glomerular capillaries, increasing the glomerular hydrostatic pressure. This increased pressure favors more filtration, thus raising the GFR.
The vasa recta are specialized blood vessels that surround the loops of Henle in juxtamedullary nephrons. Their primary role is to:
- A Actively pump sodium into the medulla
- B Filter blood plasma into the renal pyramids and calyces
- C Secrete hydrogen ions into the urine
- D Maintain medullary gradient via countercurrent exchange
Correct answer: Maintain medullary gradient via countercurrent exchange
The vasa recta act as countercurrent exchangers; they are highly permeable and pick up water and solutes in a way that preserves the osmotic gradient established by the Loop of Henle rather than washing it away.
Which nephron segment is often referred to as the 'diluting segment' because it reabsorbs solutes without water?
- A Proximal tubule
- B Descending limb
- C Thick ascending limb
- D Cortical collecting duct
Correct answer: Thick ascending limb
The thick ascending limb actively reabsorbs Na+, K+, and Cl- but is impermeable to water. This removal of solute leaves the remaining tubular fluid hyposmotic (diluted) relative to plasma.
A decrease in the plasma concentration of albumin would likely have what effect on the Net Filtration Pressure (NFP) in the glomerulus?
- A Increase NFP
- B Decrease NFP
- C No effect on NFP
- D Reverse the direction of filtration
Correct answer: Increase NFP
Albumin is the primary contributor to plasma colloid osmotic pressure, which opposes filtration. If albumin levels drop, the opposing force decreases, leading to an increase in Net Filtration Pressure.
Which of the following describes the effect of Atrial Natriuretic Peptide (ANP) on the kidney?
- A Increases GFR and decreases sodium reabsorption
- B Decreases GFR and increases sodium reabsorption
- C Stimulates the release of ADH
- D Vasoconstricts the afferent arteriole
Correct answer: Increases GFR and decreases sodium reabsorption
ANP is released by the heart in response to high blood volume. It works to lower volume by dilating the afferent arteriole (increasing GFR) and inhibiting sodium reabsorption in the collecting ducts, promoting natriuresis.
Clearance of Para-aminohippuric acid (PAH) is used clinically to estimate:
- A Total renal plasma flow
- B Glomerular filtration rate
- C Filtration fraction
- D Urine concentrating ability
Correct answer: Total renal plasma flow
PAH is both filtered and aggressively secreted, such that nearly all PAH entering the kidney is removed in a single pass. Therefore, its clearance rate provides an accurate estimate of the total renal plasma flow.