Renal Flashcards
Regarding the bladder, which of the following statements is correct?
A There is a commensurate increase in pressure as volume increases
B Sympathetic nerves initiate micturiction
C Urge to void occurs arround 150 mls
D There is a relatively constant wall tension as volume increases
C
Explanation
The tension in the bladder increases as the bladder fills but so does the radius, therefore the increase is slight until the bladder is full (Laplace’s law= 2T/R, where T is wall tension and R is the radius). Between 1-400mls there is only a slight increase in pressure to volume. Micturition is activated by the parasympathetic nervous system. The bladder also has an inherent contractile activity. The first urge to void is felt at a bladder volume of about 150ml, and a marked sense of fullness at about 400mls
Extra:
Laplace’s law isn’t really useful here because while technically correct it doesn’t really explain the importance of the compliance of the bladder wall. The bladder’s radius inherently must increase regardless of the tension and pressure, tracking the absolute volume contained. As the bladder’s volume exceeds 400mL the compliance decreases so both the pressure and tension increase even though the radius is increasing as well.
Regarding permeability and transport in the nephron, which of the following options is INCORRECT?
A Thin descending loop of Henle is permeable to water
B Thin portion of the ascending loop of Henle is permeable for NaCl
C Thick portion of the ascending loop of Henle is permeable to water
D Collecting tubule is highly permeable to water in the presence of vasopressin
C
Explanation
Loop of Henle:
The thin descending portion of the loop of Henle is highly permeable to H2O (4+) and only slightly permeable to NACL (+/-)
The thin ascending portion of the loop of Henle is not permeable to H2O (0) but highly permeable to NACL (4+)
The thick ascending portion of the loop of Henle is not permeable to H2O (0) and only slightly permeable to NACL (+/-)
The collecting tubules are only highly permeable to water in the presence of vasopressin. Without it they are only slightly permeable
Sodium is actively transported out of all parts of the renal tubule except the thin portions of the loop of Henle. 60% via PCT, 30% via thick ascending LoH, 7% via DCT and 3% via collecting ducts.
Regarding the composition of normal urine, which of the following is correct?
A No protein
B SG of 1.002 – 1.010
C pH is alkaline
D Urine output typically 500 mL/day
A
Explanation
Under normal circumstances there is neither glucose nor protein in the urine.
Note: there is always a small amount of protein in the urine. It should not exceed 150mg/day. At this level and below, there will be no protein seen on dipstix. This is not a great question but I have not altered what answer was given. The other stems are incorrect. Normal reference ranges are:
SG 1.002 – 1.030
PH is 5.5-6.5 (range 4.0-8.5) Urine output is typically 1-2L/day.
With regard to renal autoregulation, which of the following options is correct?
A Medullary blood flow is greater than cortical blood flow
B Prostaglandins increase medullary blood flow
C Prostaglandins increase cortical blood flow
D It has optimum autoregulation over an arterial blood pressure range of 60 - 100 mmHg
C
Explanation
The kidney has optimum autoregulation within an arterial blood pressure range of 90-220mmHg. Cortical blood flow is greater than medullary although the cortex has less oxygen extraction. Prostaglandins increase cortical blood flow & decrease medullary blood flow.
The filtration fraction of the kidney is approximately?
A 0.2
B 0.3
C 0.4
D 0.1
A
Explanation
Filtration fraction is 0.16-0.20
In the kidney, Na+ is most readily reabsorbed with?
A K
B Ca++
C Cl
D Glucose
C
Explanation
The reabsorption of NA and CL play a major role in electrolyte and water balance in the body. The movement of H, glucose, amino acids, organic acids, phosphate and other electrolyte substances couples sodium transport in the PCT. This co-transport occurs following a chemical gradient of sodium between the tubular cells and the instertitium. The Na/K ATPase pumps 3NA out of the tubular cells (into the interstitium) and 2K into the tubular cells (TC). Therefore there is less sodium in the TC and this allows the cotransport of tubular lumen NA into he tubular cells and then into the interstitium (and peritubular capillaries). Chloride ions are reabsorbed because they follow sodium ions due to electrical attraction. (Making CL the most ion re-absorbed with sodium)
IN the thick ascending Loop of Henle another 30% is reabsorbed via the NA-2Cl-K cotransporter
In the DCT 7% via the Na-CL cotransporter
The remainder of NA, about 3%, is absorbed via the ENac channells in the collecting ducts
Extra: The tubular locations that reabsorb chloride and the percentages of filtered chloride reabsorbed by these segments are similar to those for sodium because of constraints for electroneutrality. Any finite volume of fluid must contain equal amounts of anion and cation equivalents. There is both passive paracellular chloride reabsorption as well as active transport.
Which of the following is true with regard to bladder emptying?
A Intravesical pressures can remain constant over a range of volumes
B Voiding reflex is dependent on sympathetic control
C Parasympathetic reflex controls external urethral sphincter
D The first urge to void is at 400 mls
A
Explanation
The process of voiding:
a) The first urge to void is felt at 150ml, and a marked sense of fullness at about 400ml. The ability to maintain low pressure from 150ml to 400mls is a manifestation of the law of Laplace. This law states that the pressure in a spherical viscus is equal to twice the wall tension divided by the radius. In the case of the bladder, the tension increases as the organ fills, but so does the radius. Therefore, the pressure increase is slight until the organ is relatively full
b) Urine enters the bladder without producing much increase in intra-vesical pressure until the viscus is well filled. In addition, like other types of smooth muscle, the bladder muscle has the property of plasticity; when it is stretched, the tension initially produced is not maintained. Thus intravesical pressure can rmeian constant over a range of volumes
c) The sympathetic nerves to the bladder play no part in micturition, however in males they do mediate the contraction of the bladder muscle that prevent semen from entering the bladder during ejaculation.
d) The external urethral sphincter is controller by the pudendal nerves, which are somatic. Contraction of the perineal muscles and external sphincter can be contracted voluntarily, preventing urine from passing down the urethra or interrupting flow once urination has begun.
With a fall in systemic blood pressure, which of the following options is correct?
A There is efferent arteriolar constriction
B The filtration fraction falls
C Glomerular filtration rate (GFR) does not change
D Glomerular filtration rate (GFR) falls more than renal plasma flow
A
Explanation
During a fall in systemic blood pressure, renal plasma flow decreases more than the glomerular filtration rate (GFR) and filtration fraction increases. Both afferent and efferent arterioles are constricted but the efferents to a greater degree. Sodium retention is marked, and the nitrogenous products of metabolism are retained in the blood giving rise to azotemia and uremia. When hypotension is prolonged, renal tubular damage may be severe giving rise to acute renal failure (ARF)
The osmolality of the pyramidal papilla is?
A 800mosm/kg
B 1200mosm/kg
C 1600mosm/kg
D 400mosm/kg
B
Explanation
There is a graded increase in the osmolality of the interstitium of the pyramids, the osmolality at the tips of the papillae normally being about 1200 mosm/kg of H2O, approximately four times that of plasma.
Which of the following is best for measuring Glomerular filtration rate (GFR)?
A Inulin
B Deuterium oxide
C Tritium oxide
D Radiolabelled albumin
A
Explanation
The best substance to measure GFR is one that is freely filtered, is neither reabsorbed nor secreted, is nontoxic and not metabolized by the body. Inulin, a polymer of fructose, with a molecular weight of 5200 that is found in dahlia tubers, meets these criteria.
Extra: Historically, the gold standard for measurement of GFR has been clearance of the small molecule, Inulin has been considered an ideal filtration marker because it is freely filtered in the glomerulus and neither reabsorbed nor secreted by the tubule. Because of this, and because clearance is defined as the volume of plasma cleared entirely of a substance in a unit of time, the clearance rate of inulin equals the GFR. Direct measurement of GFR using inulin clearance is cumbersome, because it requires intravenous infusion and timed urine collection. In research studies, GFR has been measured by clearance of iothalamate, another small molecule that can be radiolabeled. Although simpler than inulin clearances, iothalamate clearance measurements are also impractical for routine clinical use.
Source: clinical evaluation of kidney function, Chi-yuan Hsu, in Primer on Kidney Disease (fifth edition), 2009
Radiolabelled albumin use to measure plasma percentage in ECF
Regarding the re-absorption of sodium in the proximal tubule, which of the following options is correct?
A Causes increasing hypertonicity
B Is pumped back into the interstitium by Na+/H+ATPase
C Shares a common carrier with glucose
D Proximal tubule reabsorbs 80% of the filtered sodium
C
Explanation
Proximal convoluted tubule (PCT) reabsorbs 60% of filtered sodium. It is pumped back into the interstitium by the Na/K-ATPase in the basolateral membrane. It does share a common carrier with glucose but this is not the primary mechanism of Na reabsorption, which is the Na/H exchange. Another 30% is absorbed via the NA-2CL-K cotransporter in the thick ascending limb of the loop of Henle, and 7% via the Na-CL cotransporter in the DCT. The remainder 3% via the ENaC channels in the collecting ducts
Summary: Na moves out of the tubular lumen by cotransport and exchange mechanisms through the apical membrane of the tubule. Sodium is then actively transported into the interstitial fluid by the NA/K ATPase in the basolateral membrane. The interstitium becomes hypertonic caused by the movement of sodium out of the PCT into the interstitium. Water moves out of the lumen into the hypertonic interstitium.
With regard to osmotic diuresis, which of the following statements is correct?
A The concentration of the urine is less than plasma
B Increased urine flow is due to decreased water reabsorption in the proximal tubule and loop of Henle
C Osmotic diuresis can only be produced by sugars such as mannitol
D Urine flows are much less than in a water diuresis
B
Explanation
Osmotic Diuresis is produced by administration of compounds such as mannitol and related polysaccharides that are filtered and not absorbed. They are also produced by substances that naturally occur but are present in amounts exceeding the capacity of the tubules to reabsorb them.
In water diuresis, the amount of water reabsorbed in the proximal portions of the nephron is normal, and the maximum urine flow that can be produced is about 16ml/min. In osmotic diuresis, increased urine flow is due to decreased water reabsorption in the PCTs and loops and very large urine flows can be produced.
In the presence of large quantities of un-reabsorbed solutes in the renal tubules cause an increase in urine flow-an osmotic diuresis. Solutes that are not reabsorbed in the PCT exert a large osmotic effect as the volume of the tubular fluid decreases and their concentration increases. They “hold water in the tubules”. Also, the concentration at which Na can be pumped out of the PCT is limited. Because of the un-reabsorbed solutes, the concentration of Na in the fluid decreases as water is held back. The loop of Henle is presented now with a greater volume of isotonic fluid. More fluid passes into the distal tubule and because of the decrease in the osmotic gradient along the medullary pyramids, less water is reabsorbed in the collecting ducts. The result is a marked increases in urine volume and excretion of Na and other electrolytes.
Renal acid secretion is affected by all the following with the exception of?
A Carbonic anhydrase
B Aldosterone
C Calcium
D PaCO2
C
Explanation
Renal acid secretion is altered by changes in the intracellular PCO2, K concentration, carbonic anhydrase level and the adrenocorticol hormone concentration (including aldosterone).
Glucose reabsorption in the kidney is?
A Closely associated with potassium
B Occurs predominantly in the distal tubule
C Resembles glucose reabsorption in the intestine
D A passive process
C
Explanation
Glucose reabsorption is an active process, it is closely associated with sodium and occurs predominantly in the proximal convoluted tubule (PCT). Sodium Glucose Linked Transporter (SGLT) are glucose cotransporters seen in enterocytes (SGLT1) and proximal tubule (SGLT2 in PCT, SGLT1 in PST), which actively reabsorb glucose.
Which of the following is the most permeable to water?
A Thin descending loop of Henle
B Cortical portion of collecting tubule
C Thick ascending limb of the loop of Henle
D Distal convoluted tubule (DCT)
A
Explanation
Nephron’s permeability to water (0 to 4+)
Thin descending LOH 4+
Thin ascending LOH 0
Thick ascending LOH 0
DCT equivocal
Cortical portion of the collecting tube 3+
Outer medullary portion of the collecting tubule 3+
Inner medullar portion of the collecting tubule 3+
Urea moves via facilitated diffusion out of the proximal tubule. It does play a role in the establishment of an osmotic gradient. It increases the ability of the kidney to concentrate urine
With regard to urea, which of the following statements is correct?
A It plays no part in the establishment of an osmotic gradient in the medullary pyramids
B There are 4 urea transporters in the kidney
C A high protein diet reduces the ability of the kidney to concentrate urine
D It moves actively out of the proximal tubule
B
Explanation
Web source:
Urea passively crosses biological membranes, but its permeability is low because of its low solubility in the lipid bilayer. Some cells speed up this process through urea transporters, which move urea by facilitated diffusion. Urea is passively reabsorbed in proximal tubule up to 50%, but its route of transport is not clear.
Current textbook :
Urea transport is mediated by urea transporters, presumable by facilitated diffusion out of the (late) proximal tubule. It does play a role in the establishment of an osmotic gradient in the medullary pyramids. It increases the ability of the kidney to concentrate urine in the collecting ducts. A high protein diet increases the ability of the kidneys to concentrate the urine. There are 4 urea transporters which mediate the facilitated diffusion. There is in fact a 5th transporter but it is found in the testis
Where in the kidney is the tubular fluid isotonic with the renal interstitium?
A Distal convoluted tubule (DCT)
B Ascending limb of the Loop of Henle
C Descending limb of the Loop of Henle
D Proximal convoluted tubule (PCT)
D
Explanation
In the PCT, water moves passively out of the tubule along the osmotic gradients set up by the active transport of solutes. This maintains isotonicity. The fluid in the descending loop of Henle becomes hypertonic as water moves out of the tubule into the hypertonic interstitium. (descending limb is permeable to water). In the ascending limb it becomes more dilute because of the movement of sodium and chloride out of the tubular lumen, and when the fluid reaches the top of the ascending limb (called the diluting segment) it is now hypotonic to plasma. The distal tubule is relatively impermeable to water, and continued removal of the solute in excess of solvent further dilutes the tubular fluid. Collecting ducts, the cortical part, in the presence of enough vasopressin to produce maximal antidiuresis, the tubular fluid becomes isotonic. This isotonic fluid then enters the medullary part of the collecting ducts where a further 4.7% or more of the filtrate is reabsorbed into the interstitium
What is the osmolality of the interstitium at the tip of the papilla?
A 800
B 1200
C 2000
D 200
B
Explanation
Active transport of NaCl (without water) in the ascending limb of the loop of Henle results in an interstitial osmolal gradient from 285 mosmol/kg (in the cortex) to 1200 mosmol/kg in the medulla at the tip of the renal papilla. This is facilitated by: 1) Passive absorption of water in the descending limb of the loop of Henle, which helps to concentrate NaCl in the tubular lumen as it enters the ascending limb and 2) Active absorption of urea from the collecting tubule under the influence of ADH.
Where in the nephron is water mostly reabsorbed?
A DCT
B Loop of Henle
C Collecting ducts
D PCT
D
Explanation
Proximal Convoluted Tubule (PCT) - Ciliated epithelium tubular lumen - Mitochondia rich and metabolically active - Leaky intercellular junctions permit bulk flow of water and solute - Isotonic fluid resorption 60-70% Na/K/H2O by end of PCT - Reuptake of nearly 100% organic molecules; 80% bicarb/phosphate; 70% Ca, 50% urea
Loop of Henle –descending loop: Permeable to water (further 15% of the filtered water is removed, impermeable to ions – ascending loop: Impermeable to water, permeable to ions, Na/K/2Cl main transporter -Creates hypertonic interstitium-fluid in the tubular lumen is hypotonic to plasma (total water reuptake presenting to the DCT is about 90%
Distal Convoluted Tubule -Mitochondria rich. - Little water uptake -Further Na uptake (to 97% total)
Collecting Ducts - Principle, type A and type B cells present - Final 2-5% sodium reabsorbed - K secreted by principle cells. - Hormones act to fine tune water re-absorption via aquaporins
Total filtered water being reabsorbed is 99.7%
All of the following conditions stimulate renin secretion EXCEPT?
A Cirrhosis
B Cardiac failure
C Supine position
D Diuretics
C
Explanation
Conditions that increase renin secretion:
Sodium depletion, diuretics, hypotension, haemorrhage, upright posture, dehydration, cardiac failure, cirrhosis, constriction of renal artery or aorta and various psychologic stimuli.
All of the following factors inhibit renin secretion EXCEPT?
A Angiotensin II
B Increased afferent arteriolar pressure
C Increased Na and CL reabsorption across macula densa
D Increased circulating catecholamines
D
Explanation
Factors that inhibit renin secretion:
- Increased Na and CL reabsorption across macula densa
- Increased afferent arteriolar pressure
- Angiotensin II
- Vasopressin
Factors that stimulate renin secretion:
- Increased sympathetic activity via renal nerves
- Increased circulating catecholamines
- Prostaglandins
Which component of the nephron contains a brush border?
A Distal convoluted tubule
B Collecting ducts
C Loop of Henle
D Proximal convoluted tubule
D
Explanation
The proximal convoluted tubule is made up of a single layer of cells that interdigitate with one another and are united by apical tight junctions. The luminal edges of the cells have a striate brush border due to the presence of innumerable microvilli
Regarding the renal handling of K, Which is INCORRECT?
A Potassium movement does not occur through the collecting ducts
B Potassium is actively reabsorbed in the proximal convoluted tubule
C Potassium excretion is decreased when the amount of Na reaching the distal tubule is small
D Potassium is secreted in the distal tubular cells
A
Explanation
Potassium (K) is actively reabsorbed in the proximal convoluted tubule
K is secreted in the distal tubular cells
In the collecting ducts K is secreted
K excretion is decreased when the amount of Na reaching the distal tubule is small, and it is also decreased when H secretion is increased
The rate of K secretion is proportionate to the rate of flow of the tubular fluid through the distal portions of the nephron, because with rapid flow there is less opportunity for the tubular K concentration to rise to a value that stops further secretion
Looking in the TB, the words excretion and excretion of potassium are used. Secretion refers to an active process and excretion to a passive. However, I don’t think it should affect the question.
A normal filtration fraction is?
A 0.2
B 0.3
C 0.4
D 0.1
A
Explanation
The ratio of the GFR to the renal plasma flow (RPF), the filtration fraction, is normally 0.16-0.2. The GFR varies less than the RPF. When there is a fall in the systemic blood pressure, the GFR falls less than the RPF because of efferent arteriolar constriction, and consequently the filtration rises
Vasopressin, which is correct?
A There are at least three kinds of vasopressin receptors
B Its effect is excretion of water in excess of solute
C Vasopressin secretion is inhibited by standing
D Decreases permeability in collecting ducts of the kidney
A
Explanation
Vasopressin also called antidiuretic hormone (ADH), increases the permeability of the collecting ducts of the kidney, so that water enters the hypertonic interstitium of the renal pyramids. The urine becomes concentrated and its volume decreases. The overall effect is retention of water in excess of solute. The effective osmotic pressure of the body fluids is decreased. There are at least 3 kinds of Vasopressin receptors - V1a, V1b, V2, the latter exerting its effects in kidney. Standing increases vasopressin secretion.
Which of the following decreases vasopressin secretion?
A Exercise
B Carbamazepine
C Alcohol
D Pain
C
Explanation
Vasopressin secretion is increased by: Increased effective osmotic pressure of plasma, decreased extracellular fluid volume, pain-emotion-stress, exercise, nausea and vomiting, standing, clofibrate, carbamazepine and angiotensin II.
Vasopressin secretion is decreased by: Decreased effective osmotic pressure of plasma, increased extracellular fluid volume and alcohol.
Ammonia is secreted into the tubular fluid as
A NH4+
B NH3+H+
C NH3OH
D NH3
D
Explanation
NH3 is lipid soluble and diffuses across the cell membranes down a concentration gradient into the interstitial fluid and the tubular urine. In the urine it reacts with H+ and forms NH4+ which remains in the urine. The process by which NH3 is secreted into the urine and then changed to NH4+, maintaining the concentration gradient for diffusion of NH3, is called nonionic diffusion. In the collecting ducts.
Extra: Ammonium (NH4+), in the proximal tubule, nonionic diffusion of NH4+ is less important as the NH4+ can be secreted into the lumen, often replacing h+ on the Na-H exchanger.
Which is true about the proximal convoluted tubule?
A The PCT starts at the macula densa of the glomerulus
B The PCT is 55um in diameter
C The PCT is 5mm long
D The PCT is found in the outer medullary portion of the kidney
B
Explanation
The PCT is 15mm long and 55um (micrometre) in diameter. Its wall is made up of a single cell layer that interdigitate with each other and is united by tight apical junctions. The luminal edges have a brush border due to microvilli. Lateral intercellular spaces are found between the bases of the cells and are extensions of the extracellular space. The PCT is found in the cortex of the kidney.
Note: The DCT is 5mm long and starts at the macula densa of the glomerulus
Which of the following hormones does the kidney NOT secrete?
A Vitamin D
B Renin
C Erythropoietin
D Aldosterone
D
Explanation
Kidney secretion of hormones
Secretion of erythropoietin which regulates red blood cell production in the bone marrow
Secretion of renin, which is a key part of the renin-angiotensin-aldosterone system
Secretion of the active form of vitamin D and prostaglandins
Aldosterone is a mineralocorticoid hormone produced by the outer section (zona glomerulosa) of the adrenal cortex
What is the action of aldosterone on the kidneys
A Promotes sodium and bicarbonate reabsorption
B Promotes sodium and hydrogen secretion
C Promotes sodium reabsorption and water secretion
D Promotes sodium reabsorption and potassium secretion
D
Explanation
Aldosterone is a mineralcorticoid. Aldosterone promotes Na+ and water retention, and lower plasma K+ concentration by the following mechanisms:
- Acting on the distal tubule and collecting duct of the kidney nephron, it up regulates and activates the basolateral Na/K pumps, which pumps three sodium ions out of the cell and two potassium ions into the cell. This results in reabsorption of sodium and water into the blood, and secretion potassium into the urine
- Aldosterone upregulates epithelial sodium channels increasing apical membrane permeability for Na+.
- Chloride is reabsorbed in conjunction with sodium cations to maintain the system’s electrochemical balance.
- Aldosterone stimulates the secretion of K+ into the tubular lumen
- Aldosterone stimulates Na+ and water reabsorption from the gut, salivary and sweat glands in exchange for K+.
- Aldosterone stimulates secretion of H+ in exchange for Na+ in the intercalated cells of the cortical collecting tubules regulating plasma bicarbonate levels and acid/base balance
Which of the following regarding the glomerular filtration rate (GFR) is correct
A 90% of filtrate is reabsorbed by the kidney
B Creatinine clearance can be used to measure the glomerular filtration rate
C The GFR is approximately 10L/h
D A fall in systemic blood pressure the glomerular filtration rate falls more than the renal plasma flow
B
Explanation
The GFR is approximately 125ml/min or 7.5l/h or 180L/day. The normal production of urine a day is 1L. Therefore 99% or more of the filtrate is normally reabsorbed
Factors controlling the GFR include: size of the capillary bed, permeability of the capillary bed (50 times that of skeletal muscle), and the hydrostatic and oncotic pressures gradients across the capillary beds
Creatinine clearance rate is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR, despite the fact that creatinine is secreted and reabsorbed by the tubules. Therefore the plasma creatinine clearance can be inaccurate at low levels.
The filtration fraction is the ratio of the GFR to the renal plasma flow (RPF) and is normally 0.16-0.2. When there is a fall in systemic blood pressure the GFR falls less than the RPF due to the constriction of the efferent arterial
What percentage of filtered glucose is reabsorbed in the proximal tubule?
A 85-90%
B 90-95%
C > 95%
D < 85%
C
Explanation
Reabsorption of glucose occurs in the early part of the PCT via secondary active transport with Na. Normally all is reabsorbed, unless the renal threshold of filtration is exceeded.
Extra:
Glucose, amino acids, and bicarbonate are reabsorbed along with Na+ in the early portion of the proximal tubule. Glucose is typical of substances removed from the urine by secondary active transport. Ganong no longer lists a specific value, but Figure 37-13 demonstrates that all glucose reabsorption occurs in the proximal tubule
Which part of the tubule does not reabsorb sodium?
A Descending limb of loop of Henle
B Ascending limb of loop of Henle
C Distal tubule
D Proximal tubule
A
Explanation
60% of Na reabsorption occurs in the PCT via Na/H exchangers and SGLT-2,
30% in the TAL of the LOH via Na/K/2Cl co-transporters,
7% in the DCT via Na/Cl co-transporter,
3% in the collecting ducts via ENaC channels.
The thin descending limb of the LOH is responsible for water movement but not solute movement.
Which of the following affects renal acid secretion?
ANa concentration
B Serum glucose concentration
C Peripheral chemoreceptors
D Carbonic anhydrase inhibitors
D
Explanation
Carbonic anhydrase enzyme catalyses the conversion of CO2 to H+ and HCO3- in tubular cells of the proximal tubule and thus facilitates H+ secretion.
Which part of the renal tubule is most sensitive to the effects of aldosterone?
A Loop of Henle
B Distal tubule
C Collecting duct
D Proximal tubule
C
Explanation
Aldosterone acts on principal (P) cells of the collecting ducts, increasing Na exchange for K and also increasing H secretion.
Angiotensin II stimulates the release of:
A Aldosterone
B Serotonin
C Testosterone
D Cortisol
A
Calculate the GFR for this person with these values:
Haematocrit 40%, Inulin (plasma) 0.25mg/mL, Inulin (urine) 35mg/ml, urine volume 1ml/min
A 140ml/min
B 200ml/min
C 280ml/min
D 100ml/min
A
Explanation
Clearance of inulin = (Urine concentration x urine flow) / Arterial plasma level. Therefore 35 x 1 / 0.25 = 140.
Haematocrit is used to calculate renal blood flow.
The counter current multiplication in the kidneys relies on what property
A Passive transport of sodium and chloride out of the thick ascending limb
B Outflow of tubular fluid from the proximal tubule
C Inflow of fluid into the distal tubule
D Permeability of the thin descending limb of Loop of Henle to water
D
Explanation
The operation of each loop of Henle as a countercurrent multiplier depends on the high permeability of the thin descending limb to water (via aquaporin-1), the active transport of Na+ and Cl− out of the thick ascending limb, and the inflow of tubular fluid from the proximal tubule, with outflow into the distal tubule. It is also important to remember that the equilibrium is maintained unless the osmotic gradient is washed out
