Pre Clinical Medical Science SBAs
Pre Clin Renal: (49 questions)

Questions

• 1
  Which part of the nephron is always impermeable to water?
  Difficulty: Easy     Topic: Water permeability
  a

  Collecting duct

  b

  Descending limb

  c

  Distal convoluted tubule

  d

  Proximal convoluted tubule

  e

  Thick ascending limb
  Explanation: The thick ascending limb of the loop of Henle is impermeable to both water and solutes except for the Na-K-Cl co-transporter that acts to remove solutes, creating a hypertonic medullary interstitium with a hypotonic lumen. All other areas may be permeable to either or both. The collecting duct may be impermeable to water in the absence of ADH.
• 2
  What epithelium is present in the ureters?
  Difficulty: Easy     Topic: Renal System
  a

  Pseudostratified columnar

  b

  Simple columnar

  c

  Simple cuboidal

  d

  Stratified squamous

  e

  Transitional
  Explanation: The ureters (and bladder) have a transitional epithelium. This is composed of irregularly arranged squamous cells that are able to slide over each other. A transitional cell carcinoma is the most common renal tract cancer.
• 3
  What are the boundaries of the trigone?
  Difficulty: Easy     Topic: Trigone
  a

  The area adjacent to the the prostate in men

  b

  The bladder fundus and the level of the pubic bone

  c

  The superior and inferior vesical arteries

  d

  The ureters and the median umbilical ligament

  e

  Two ureterovesical openings and the internal urethral orifice
  Explanation: The trigone is a triangular area in the bound by the two ureterovesical valves and the internal urethral orifice. This area of the mucosa is smooth (without rugae) because it is closely adhered to the underlying tissues, unlike the rest of the bladder.
• 4
  What is the main role of sympathetic nerve supply to the bladder?
  Difficulty: Easy     Topic: Sympathetic supply
  a

  Detrusor contraction

  b

  Detect urethral flow

  c

  External urethral sphincter tone

  d

  Internal urethral sphincter tone

  e

  Rugae contraction
  Explanation: Sympathetic nerves from T12-L2 pass through the superior and inferior hypogastric plexi to the neck of the bladder. Stimulation increases smooth muscle contraction, to prevent passage of urine.
• 5
  Where do the parasympathetic neurones innervating the bladder originate from?
  Difficulty: Easy     Topic: Parasympathetic supply
  a

  Inferior hypogastric plexus

  b

  Pudendal nerve

  c

  Superior mesenteric ganglion

  d

  T12-L2

  e

  Vagus
  Explanation: The parasympathetic supply to the bladder is part of the sacral outflow from S2-4 which passes through the superior and inferior hypogastric plexi. This innervates the detrusor to cause contraction and promote micturition. The pudendal nerve is a somatic nerve that passes to the external urethral sphincter.
• 6
  What is the reflex response to the flow of urine in the urethra?
  Difficulty: Easy     Topic: Micturition reflexes
  a

  External urethral sphincter contraction

  b

  External urethral sphincter relaxation

  c

  Inhibition of detrusor contraction

  d

  Internal urethral sphincter relaxation

  e

  Vesical artery vasoconstriction
  Explanation: The flow of urine in the urethra (at the start of micturition) demonstrates positive feedback by signalling through parasympathetic afferents, then efferents, to cause detrusor contraction and relaxation of the internal sphincter.
• 7
  Approximately what percentage of extracellular fluid volume is plasma?
  Difficulty: Hard     Topic: Body fluid compartments
  a

  10

  b

  20

  c

  30

  d

  40

  e

  50
  Explanation: In a 70Kg adult, approximately 45Kg of total mass is water (60-65%). Of this, 30L is intracellular and 15L is extracellular. Total blood volume is just over 5L, of which around 3L is plasma (given a haematocrit of 40-45%). Therefore 3L plasma is 20% of 15L total extracellular fluid, where the remaining 12L is interstitial fluid.
• 8
  How do Starling’s forces change from afferent to efferent end of the glomerular capillaries?
  Difficulty: Easy     Topic: Starling's forces
  a

  Falling hydrostatic pressure in Bowman's space

  b

  Increasing capillary hydrostatic pressure

  c

  Increasing capillary oncotic pressure

  d

  Increasing oncotic pressure in Bowman's space

  e

  No change along the capillary length
  Explanation: Along the glomerular capillaries a large amount of fluid passes out into Bowman's space, which increases the hydrostatic pressure in Bowman's space but reduces it in the capillaries. Due to fluid loss, the capillary plasma proteins become more concentrated, causing a rise in capillary oncotic pressure. There should be no change in Bowman space oncotic pressure because normally no protein pass through filtration.
• 9
  What is meant by “glucose demonstrates a tubular maximum for reabsorption”?
  Difficulty: Easy     Topic: Tubular maximum
  a

  All filtered glucose is excreted

  b

  Reabsorption is active up to a fixed point, above which is passive

  c

  Reabsorption is passive up to fixed point, above which it is active

  d

  There is a fixed maximum reabsorption rate

  e

  There is no limit to glucose reabsorption
  Explanation: A tubular maximum describes a substance that is completely removed from the filtrate by reabsorption (active or passive) up to a fixed rate. Such that when the concentration of this substance (e.g. glucose) in the filtrate exceeds this, it cannot be completely reabsorbed and appears in the urine.
• 10
  How do the afferent and efferent arterioles differ?
  Difficulty: Easy     Topic: Afferent & efferent arterioles
  a

  Angiotensin-II has preferential action on the efferent arteriole

  b

  Greater pressure fall in the afferent arterioles

  c

  Hydrostatic pressure is higher in the efferent arterioles

  d

  Only the afferent arteriole is followed by a capillary bed

  e

  Only the afferent arteriole is under sympathetic control
  Explanation: Angiotensin-II causes more vasoconstriction at the efferent arteriole than the afferent arteriole. This acts to help maintain GFR in low blood pressure states and to promote reabsorption of fluid in the peritubular capillaries. The pressure fall is greater in the efferent arterioles and they have a lower pressure. Both are followed by capillary beds and are under sympathetic control.
• 11
  In a healthy individual with a renal blood flow of 1100ml/min, what is the approximate renal plasma flow?
  Difficulty: Medium     Topic: Renal plasma flow
  a

  400ml/min

  b

  500ml/min

  c

  600ml/min

  d

  700ml/min

  e

  800ml/min
  Explanation: Plasma flow is determined by the haematocrit and renal blood flow. Given a haematocrit of 40-45% and a blood flow of 1100ml/min (normal), renal plasma flow is approximately 600ml/min. This figure is needed to calculate the filtration fraction, which is GFR / renal plasma flow (120 / 600 = 20%)
• 12
  What is the main transporter for sodium reabsorption in the proximal convoluted tubule?
  Difficulty: Easy     Topic: Sodium absorption
  a

  Antiporter with H+

  b

  Antiporter with K+

  c

  Co-transport with amino acids

  d

  Co-transport with glucose

  e

  Co-transporter with H+ ions
  Explanation: Most sodium uptake in the PCT occurs via sodium-hydrogen antiporter. This is driven by the sodium concentration gradient established by the sodium-potassium pump on the basolateral membrane, which causes efflux of sodium. Co-transport with glucose and amino acids also occur.
• 13
  How is most water absorbed in the proximal convoluted tubule?
  Difficulty: Medium     Topic: PCT water reabsorption
  a

  Apical aquaporins controlled by ADH

  b

  Basal aquaporins

  c

  Constitutive apical aquaporins

  d

  Paracellular transport

  e

  Transcellular passage by diffusion
  Explanation: There are two forms of aquaporin channels: constitutive (always present) and inducible (under control of ADH). Constitutive channels are found in the PCT - they are always active and permit transcellular movement of water by osmosis. Inducible aquaporin channels have the same function, but only become present under the action of ADH - they are in the DCT and collecting ducts.
• 14
  What is meant by a ‘horseshoe’ kidney?
  Difficulty: Hard     Topic: Horseshoe kidney
  a

  A form of renal tumour

  b

  Normal shape of a kidney

  c

  Single kidney that crosses the aorta anteriorly

  d

  Single kidney that crosses the aorta posteriorly

  e

  Two kidneys shaped like a horseshoe
  Explanation: A horseshoe kidney is an anatomical renal malformation where there is an abnormal connection between the two kidneys anterior to the aorta, just inferior to the origin of the superior mesenteric artery. It is associated with increased risk of renal stones and chronic kidney disease.
• 15
  How the vasa recta maintain the hypertonic medullary interstitium?
  Difficulty: Easy     Topic: Vasa recta
  a

  They are impermeable to potassium

  b

  They are impermeable to sodium

  c

  They are impermeable to water

  d

  They are permeable to water and solutes

  e

  They are permeable to water but not solutes
  Explanation: The vasa recta are the capillaries supplying the renal medulla and loop of Henle. They are completely permeable to solutes and water, which allows their contents to equilibrate with the interstitium. Therefore they prevent wash-out of the hypertonic interstitium as water exits the descending limb at the top and re-enters the ascending limb, which solutes exit the ascending limb at the base and enter the descending limb.
• 16
  How is urea handled by the collecting duct (CD)?
  Difficulty: Medium     Topic: Urea handling
  a

  Active reabsorption of urea

  b

  Active secretion of urea

  c

  Cortical CD is permeable, medullary CD is impermeable

  d

  CD is totally impermeable

  e

  Cortical CD is impermeable, medullary CD is permeable
  Explanation: The medullary part of the CD is permeable to urea to allow equilibration with the hypertonic medullary interstitium. This has two effects: urea contributes to the hypertonicity, and it prevent urea exerting an intraluminal osmotic effect. If urea remained intraluminal then water would be held within the tubule lumen by osmosis, causing excess diuresis.
• 17
  What is renal clearance?
  Difficulty: Easy     Topic: Clearance 1
  a

  The amount of a substance that is filtered from plasma in unit time

  b

  The amount of a substance that is removed from blood in unit time

  c

  The amount of a substance that is removed from plasma in unit time

  d

  The volume of plasma that a given substance is removed from in unit time

  e

  The volume of plasma that is filtered in unit time
  Explanation: Clearance is the volume of plasma that is removed of a substance in unit time. It is calculated for a particular substance (e.g. creatinine) and then that may be equivalent to glomerular filtration rate or give other information about renal function.
• 18
  Given that: substance X is filtered and secreted so the concentration in the renal vein is zero. What is the clearance of substance X equivalent to?
  Difficulty: Medium     Topic: Clearance 2
  a

  Cardiac output

  b

  Creatinine clearance

  c

  Glomerular filtration rate

  d

  Renal blood flow

  e

  Renal plasma flow
  Explanation: If a substance is completely removed from renal (arterial) blood flow by a combination of filtration and secretion of all unfiltered substance, then it’s clearance is equal to renal plasma flow. This is because the entire volume of renal plasma is cleared of this substance (e.g. the organic acid PAH).
• 19
  What change causes the most rapid increase in ADH secretion?
  Difficulty: Medium     Topic: ADH secretion
  a

  A fall in blood osmolality

  b

  A fall in blood pressure

  c

  A rise in blood osmolality

  d

  A rise in blood pressure

  e

  An increase in urine output
  Explanation: Antidiuretic hormone is released from the supraventricular and paraventricular nuclei in the hypothalamus. Its release increases with increasing plasma osmolality or a fall in blood pressure, and the combination of the two are synergistic however a fall in blood volume has the dominant effect.
• 20
  What is the target for renin?
  Difficulty: Easy     Topic: Renin
  a

  Aldosterone

  b

  Angiotensin

  c

  Angiotensin-II

  d

  Angiotensinogen

  e

  Granular cells
  Explanation: Renin is released by granular cells in response to a fall in renal perfusion, fall in GFR or sympathetic stimulation. Renin cleaves circulating angiotensinogen into angiotensin. ACE (angiotensin converting enzyme) breaks down angiotensin into angiotensin-II, which exerts a number of actions including stimulating release of aldosterone.
• 21
  Which of the following is NOT an action of angiotensin-II?
  Difficulty: Easy     Topic: Angiotensin-II
  a

  Increased ADH release

  b

  Increased aldosterone release

  c

  Increased potassium secretion

  d

  Increased sodium reabsorption

  e

  Vasoconstriction
  Explanation: Angiotensin-II has 4 main actions: promotes sodium reabsorption, causes aldosterone release, vasoconstriction (especially of efferent arteriole) and stimulates ADH release. Aldosterone promotes potassium secretion (and sodium uptake).
• 22
  Which hormone is released in response to volume overload and causes sodium loss in the kidneys?
  Difficulty: Easy     Topic: Volume overload
  a

  Aldosterone

  b

  Angiotensin-II

  c

  Anti-diuretic hormone

  d

  Atrial natriuretic peptide

  e

  Renin
  Explanation: Atrial natriuretic peptide (ANP) is a hormone released in response to right atrial stretch, which indicates increased venous return secondary to a raised blood volume. It promotes loss of sodium in the urine (natriuresis), with water. B-type natriuretic peptide (BNP) performs a similar function and is released from ventricular myocytes.
• 23
  What circulation is least affected by sympathetic vasoconstriction during hypotension?
  Difficulty: Easy     Topic: Sympathetic vasoconstriction
  a

  Cerebral

  b

  Cutaneous

  c

  Gastrointestinal

  d

  Skeletal muscle

  e

  Renal
  Explanation: In response to hypotension there is activation of the sympathetic nervous system to compensate, which includes alpha-adrenoreceptor mediated vasoconstriction. This is most prominent in the skin, gut, kidney and skeletal muscle. The brain is almost entirely unaffected, as is the heart.
• 24
  What electrolyte abnormality frequently occurs with acute renal failure?
  Difficulty: Easy     Topic: Acute renal failure
  a

  Hypercalcaemia

  b

  Hyperkalaemia

  c

  Hypermagnesaemia

  d

  Hypernatraemia

  e

  Hyperphosphataemia
  Explanation: One of the main roles of the kidney is potassium regulation. It is excreted in the distal tubule and collecting duct in proportion to flow rate and under the action of aldosterone. In renal failure this process does not occur and there is accumulation of potassium in the serum. The other ions listed are often low in acute renal failure due to loss in the urine.
• 25
  What is the normal role of prostaglandins in the proximal convoluted tubule?
  Difficulty: Easy     Topic: Prostaglandins
  a

  Vasoconstrict and increase H+-ATPase activity

  b

  Vasoconstrict and increase Na-K-ATPase activity

  c

  Vasoconstrict and reduce Na-K-ATPase activity

  d

  Vasodilate and increase Na-K-ATPase activity

  e

  Vasodilate and reduce Na-K-ATPase activity
  Explanation: Prostaglandins have a protective role in the kidney by vasodilating (to increase oxygen delivery) and inhibiting the sodium-potassium pump (to reduce energy expenditure). Therefore prostaglandin inhibitors (e.g. NSAIDs) may cause renal failure by antagonising these effects.
• 26
  Which muscle lies immediately posterior to the lateral part of the inferior renal pole?
  Difficulty: Hard     Topic: Kidney relations 2
  a

  Gluteus medius

  b

  Iliacus

  c

  Psoas major

  d

  Quadratus lumborum

  e

  Transversus abdominus
  Explanation: Posterior to the kidney there is mostly muscle, plus ribs and the lateral vertebral processes. Psoas major and minor begin medially and run inferolaterally towards the hip so cover the medial part of the lower pole. Quadratus lumborum attaches to the lumbar vertebrae and covers the lateral part. The other muscles have a less close relationship to the kidneys.
• 27
  How are podocytes specialised?
  Difficulty: Medium     Topic: Glomeruli 2
  a

  High Na+/K+-ATPase activity

  b

  Fenestrated

  c

  Interditigation of foot processes

  d

  Positively charged

  e

  Possess a glycocalyx
  Explanation: Podocytes are epithelial cells of Bowman's capsule. They have projections from their cell body called 'foot processes' that wrap around glomerular capillaries. Foot processes interdigitate with each other and the spaces between are called slit pores. High Na/K-ATPase activity is in tubular cells. Glomerular capillaries are fenestrated. The glomerular basement membrane is negatively charged to repel proteins. The glomerular endothelial is covered in a thin gylcocoalyx.
• 28
  In the absence of other changes, what is the effect of afferent arteriole constriction on filtration?
  Difficulty: Easy     Topic: GFR
  a

  Decreased GFR

  b

  Decreased natriuresis

  c

  Increased GFR

  d

  Increased proteinuria

  e

  No change
  Explanation: Constriction of the afferent arteriole reduces hydrostatic pressure distal to the vessel and increases pressure proximal to the vessel. This reduces the pressure for ultrafiltration in the glomeruli. Normally the efferent arteriole will constrict at the same time to maintain GFR, but in the absence of this GFR would fall. Sodium or protein loss in the urine would be unaffected.
• 29
  What is the normal response to increased renal artery pressure?
  Difficulty: Medium     Topic: Perfusion pressures
  a

  Afferent arteriole constriction

  b

  Afferent arteriole dilatation

  c

  Efferent arteriole constriction

  d

  Efferent arteriole dilatation

  e

  Increased GFR
  Explanation: An increase in hydrostatic pressure in the renal artery causes increased stretch of myocytes in the afferent arteriole. This stimulates the myogenic reflex to cause constriction, which reduces glomerular perfusion pressure back to baseline - maintaining GFR.
• 30
  What is the function of the macula densa?
  Difficulty: Medium     Topic: Macula densa
  a

  Cause afferent arteriole constriction in response to low GFR

  b

  Cause afferent arteriole constriction in response to low GFR

  c

  Cause aldosterone release in response to high GFR

  d

  Cause renin release in response to high tubular sodium

  e

  Cause aldosterone release in response to low tubular sodium
  Explanation: The macula densa is a group of cells in the wall of the distal convoluted tubule, part of the juxtaglomerular apparatus. They are activated by a fall in tubular sodium, which is a marker for a fall in GFR. In response they release factors that dilate the afferent arteriole and stimulate release of renin from adjacent granular cells. The effect is to raise systemic blood pressure and maintain GFR.
• 31
  What is the renal response to an acute respiratory acidosis?
  Difficulty: Medium     Topic: Acid-base 1
  a

  Increase H+ reabsorption

  b

  Increase lumenal H+ secretion

  c

  Increase lumenal H2CO3 secretion

  d

  Decrease lumenal phosphate secretion

  e

  Reduce de novo HCO3- generation
  Explanation: Acute acidosis causes an increase in tubular cell H+ ion concentration, which raises the rate of H+ ion secretion, HCO3- generation and HCO3- reabsorption. This acts to compensate for raised serum H+. Lumenal phosphate secretion increases to bind H+ and cause its loss in the urine.
• 32
  How is bicarbonate reabsorbed from the proximal tubule lumen?
  Difficulty: Medium     Topic: Bicarbonate
  a

  As CO2 + H2O

  b

  Through gap junctions

  c

  Via chloride-bicarbonate antiporter

  d

  Via sodium-bicarbonate symporter

  e

  Via a specific bicarbonate channel
  Explanation: Bicarbonate reacts with H+ under the action of carbonic anhydrase on the tubular cell brush border to form CO2 + H2O, which are then able to diffuse through the apical membrane into tubular cells.
• 33
  What is the role of ammonia in acid-base status?
  Difficulty: Hard     Topic: Ammonia
  a

  Binds lumenal H+ to form NH4+

  b

  Binds lumenal HCO3- for reabsorption

  c

  Converts strong acids to weak acids

  d

  Provides an alkaline buffer

  e

  Provides a source of bicarbonate
  Explanation: Ammonia is generated by deamination of glutamate. It is exported into the lumen and binds H+ to form NH4+ in the lumen. NH4+ is not reabsorbed so stays in the lumen and is lost in the urine. Whilst an alkaline ion, its main role is not as a serum buffer.
• 34
  What mechanism causes an increase in renal compensation during systemic acidosis?
  Difficulty: Hard     Topic: Acid-base 2
  a

  Increased activity of apical tubular H+ transporters

  b

  Increased activity of carbonic anhydrase

  c

  Increased enzyme activity for HCO3- synthesis

  d

  Reduced activity of carbonic anhydrase

  e

  Reduced activity of phosphate transporters
  Explanation: In acidosis there is increased tubular cell H+ concentration, which has a direct effect of activating apical H+ transporters. The acidosis also activates protein kinases that in turn further stimulate apical transporters. The other mechanisms listed do not have a significant role.
• 35
  How do thiazide diuretics act?
  Difficulty: Medium     Topic: Thiazides
  a

  Block action of ADH

  b

  Exert osmotic effects in tubular lumen

  c

  Inhibit action of aldosterone

  d

  Inhibition of sodium-chloride co-transporter

  e

  Inhibition of sodium-chloride-potassium co-transporter
  Explanation: Thiazides inhibit a sodium-chloride co-transporter in the distal convoluted tubule. Tetracyclines inhibit ADH. Mannitol is an osmotic diuretic. Spironolactone is an aldosterone antagonist. Loop diuretics block the sodium-potassium-chloride transporter in the loop of Henle.
• 36
  Which diuretic is most potent at causing diuresis?
  Difficulty: Hard     Topic: Diuretics
  a

  Acetazolamide

  b

  Bendoflumethiazide

  c

  Furosemide

  d

  Mannitol

  e

  Spironolactone
  Explanation: Loop diuretics (e.g. furosemide) are the most potent at increasing diuresis. This is because they inhibit the sodium-chloride-potassium co-transporter in the loop of Henle which is the key transporter for establishing a hypertonic medullary interstitium. Without this, there is no water reabsorption through the collecting ducts.
• 37
  What is the anatomical position of the kidneys?
  Difficulty: Easy     Topic: Kidney relations 1
  a

  From T10-L1

  b

  In the iliac fossae

  c

  In the paravertebral gutter and peritoneal cavity

  d

  The left hilum passes through the transpyloric plane

  e

  The right inferior pole is covered by the 12th rib
  Explanation: The right kidney lies slightly lower than the left due to the presence of the liver. The left hilum is at the level of the transpyloric plane (L1) but the right superior pole lies at this level. The kidneys span from T12-L3. Transplanted kidneys are often placed in the iliac fossae. Kidneys are retroperitoneal. The 12th rib crosses the middle of the kidneys.
• 38
  What structures comprise the glomerular filtration barrier?
  Difficulty: Easy     Topic: Glomeruli 1
  a

  Endothelial cells, basement membrane

  b

  Endothelial cells, basement membrane, podocytes

  c

  Endothelial cells, podocytes

  d

  Podocytes, basement membrane

  e

  Tubular cells, basement membrane
  Explanation: The filtration barrier describes the structures between blood in the glomerular capillaries and the filtrate present in Bowman's capsule. Firstly there are fenestrated glomerular capillary endothelial cells, which sit on a basement membrane. These are supported by epithelial cells called podocytes that have interdigitating foot processes wrapping around the capillaries.
• 39
  Which part of the duodenum has the closest relation to the right kidney?
  Difficulty: Medium     Topic: Kidney relations 3
  a

  1st

  b

  2nd

  c

  3rd

  d

  4th

  e

  5th
  Explanation: The anterior relations of the right kidney are: the liver, ascending colon and hepatic flexure and the 2nd part of the duodenum. There is no 5th section to the duodenum.
• 40
  What lies immediately outside the renal capsule?
  Difficulty: Medium     Topic: Renal coverings
  a

  Arcuate arteries

  b

  Gerota's fascia

  c

  Paranephric fat

  d

  Perinephric fat

  e

  Renal cortex
  Explanation: The kidney has 4 main coverings: the renal capsule (hard fibrous tissue), perinephric fat, Gerota's fascia (the renal fascia) and then para nephric fat. Posterior are muscles and bone and anterior is viscera.
• 41
  The path taken by the ureters is similar to the course of which muscle?
  Difficulty: Easy     Topic: Ureters 1
  a

  Erector spinae

  b

  Iliacus

  c

  Psoas major

  d

  Quadratus lumborum

  e

  Rectus abdominus
  Explanation: The ureters leave the renal hilum and pass inferolaterally. Their course mirrors that of psoas major (and minor) that runs from the lateral vertebral processes to the lesser trochanter of the femur.
• 42
  What is a renal pyramid?
  Difficulty: Medium     Topic: Renal pyramid
  a

  A 6th of a kidney

  b

  All the collecting ducts drain into one minor calyx

  c

  All the minor calyces drain into one major calyx

  d

  All the nephrons drain into one collecting duct

  e

  Area supplied by one arcuate artery
  Explanation: Each kidney has 7-18 pyramids, whose bases project towards the cortical surface and each drain into a papilla that feeds into a minor calyx. Several minor calyces compose a major calyx, of which each kidney has 3-4 that forms the pelvis.
• 43
  What percentage of nephrons pass into the deep medulla?
  Difficulty: Hard     Topic: Medullary nephrons
  a

  25%

  b

  35%

  c

  45%

  d

  55%

  e

  65%
  Explanation: There are two kinds of nephron: cortical and juxtamedullary. Juxtamedullary nephrons have long loops of Henle that pass deep into the medulla and contribute to the hypertonic interstitium, they are only 15-25% of all nephrons. Cortical nephrons are much more numerous and do not contribute to the medullary interstitial gradient.
• 44
  Where do the renal arteries branch from the abdominal aorta?
  Difficulty: Medium     Topic: Renal arteries
  a

  At the level of L3

  b

  Inferior to the gonadal arteries

  c

  Inferior to the superior mesenteric artery

  d

  Superior to the Coeliac trunk

  e

  Superior to the middle suprarenal arteries
  Explanation: The left renal artery branches at L1-2 with the right slightly below this. The Coeliac trunk originates and T12 and the superior mesenteric artery at L1, just above the renal vessels. The gonadal arteries are below this nearer L2.
• 45
  Which vessels branch off renal arcuate arteries?
  Difficulty: Medium     Topic: Renal blood supply
  a

  Afferent arterioles

  b

  Efferent arterioles

  c

  Interlobar arteries

  d

  Interlobular arteries

  e

  Segmental arteries
  Explanation: The renal arteries branch off the aorta, enter the kidneys and separate into the segmental arteries. Interlobar arteries ascend between renal pyramids to the level of the base of renal pyramids. They turn 90-degrees and become the arcuate arteries that pass in parallel with the base of the pyramids. These give off the interlobular arteries that run downwards to nephrons and give off afferent arterioles.
• 46
  How many segmental arteries are present in each kidney?
  Difficulty: Hard     Topic: Segmental arteries
  a

  3

  b

  4

  c

  5

  d

  6

  e

  7
  Explanation: Each renal artery branches into 5 segmental arteries (which can be equated to the lobar arteries of the lungs): apical, lower, posterior, anterior upper and anterior middle.
• 47
  Where do the ureters cross the pelvic brim?
  Difficulty: Easy     Topic: Ureters 2
  a

  At the bifurcation of the iliac vessels

  b

  At the origin of the median sacral artery

  c

  At the origin of the inferior vesical artery

  d

  At the origin of the superior vesical artery

  e

  Posterior to psoas major
  Explanation: The ureters pass inferiorly from the renal hilum in line with psoas major and over the transverse vertebral processes. They cross the pelvic brim at the point of bifurcation of the iliac artery to the internal and external iliac.
• 48
  What form of smooth muscle contraction is displayed by the ureter?
  Difficulty: Medium     Topic: Ureteric contraction
  a

  Continuous (tonic)

  b

  Inducible peristalsis

  c

  No contraction

  d

  Spontaneous, intermittent peristalsis

  e

  Spontaneous segmentation
  Explanation: The ureters contain 2 layers of smooth muscle in their upper 2/3 and 3 layers in the lower 1/3. This mediates spontaneous peristalsis with periods of increasing, then decreasing contraction. In contrast to intestinal smooth muscle, it is relatively independent of other factors. This mediates the colicky pain experienced by renal stones.
• 49
  Which vessel supplies blood to the middle 1/3 of the ureter?
  Difficulty: Medium     Topic: Ureter blood supply
  a

  External iliac artery

  b

  Gonadal artery

  c

  Internal iliac artery

  d

  Renal artery

  e

  Superior vesical artery
  Explanation: There are several arteries that contribute supply of the ureters. The renal arteries and aorta supply the upper parts, then the gonadal arteries provide most of the blood to the middle 1/3. The lower 1/3 of the ureter is supplied by the internal iliac arteries.