Urinary System
Calculate the net filtration pressure if capillary hydrostatic pressure is 60 mm Hg, capillary osmotic pressure is 25 mm Hg, and capsular hydrostatic pressure is 10 mm Hg.
25 mm Hg
Which hormone had the greater effect on urine volume?
ADH
In severe dehydration or blood loss, what would be the levels of ADH and what would be the urine flow rate?
ADH - high; low urine flow rate (0.25 ml/min)
In overhydration, what would be the levels of ADH (high, normal, or low) and what would be the osmolarity of the urine?
ADH - low; 100 mOsm (urine)
Which of the following statements about ADH (antidiuretic hormone) is correct?
ADH is released by the posterior pituitary gland.
Which of the following statements about aldosterone is NOT correct?
Aldosterone increases sodium reabsorption by increasing the number of Na+-K+ ATPase pumps in the luminal membrane of the proximal tubule.
Identify the correct direction of urine flow from formation to exiting the kidney.
Cortex, medulla, renal pelvis, ureter
Lisa suffers from kidney stones. One small stone manages to get lodged in the ascending limb of the nephron loop of one of her nephrons. Predict what would happen to the amount of filtrate produced over time by this particular nephron.
Decrease in filtrate production due to an increase in hydrostatic pressure in the capsular space
Hypertensive kidney failure would most likely result in which of the following conditions?
Increased retention of creatinine
Which of the following was NOT observed during this activity?
Increasing the rate of filtration increased the concentration of solutes in the filtrate.
An example of filtration occurs in the kidney and:
Ions and glucose filter from the capillary into the kidney tubule.
Which component, of those listed below, has the lowest concentration (mEq/L or mg/dL) in both plasma and dialysis fluid?
K+
Which of the following transporters in the luminal membrane results in secretion?
Na+Na+-H+H+ countertransport
Which event does not occur in the distal convoluted tubule?
Osmosis pulls water out of the tubular fluid and into the peritubular fluid.
Which nephron part do you think will be most at risk of damage due to chronic hypertension?
Renal corpuscle
Which event correctly occurs under maximum ADH stimulation?
The DCT and collecting system become more permeable to water.
Tracey knows that the large pizza Max consumed just prior to collecting his third urine sample caused a transient increase in his blood glucose levels. What can be accurately said about the relationship between glucose in the blood and the amount of glucose filtered through the glomerular membrane?
The higher the blood glucose concentration, the more glucose is filtered through the glomerular membrane.
What does the color of Max's urine tell Tracey about how concentrated or dilute it is? How does Max's urine color/concentration compare to the urine specific gravity at the same time?
The pale urine is dilute, the yellow is more concentrated and dark is very concentrated.Specific gravity is the ratio of the density of a substance compared to the density of an equal volume of distilled water. Urine has a greater specific gravity than water which varies depending on the concentration solute. The more concentrated the urine, the darker its color and higher specific gravity.
Which statement regarding the kidneys is false?
The right kidney lies slightly superior to the left kidney.
What happened to the urine concentration when the solute gradient in the interstitial space was increased?
The urine concentration increased.
What happened to the urine volume when the solute gradient in the interstitial space was increased?
The urine volume decreased.
What will happen to the urine volume if ADH is NOT added to the collecting duct?
The urine volume will increase.
During reabsorption of water in the proximal convoluted tubule, what causes water to diffuse from the lumen into the interstitial space?
an increase in the osmolarity of the interstitium
the secretion of aldosterone is directly stimulated by _______
angiotensin II
As diffusion takes place across the dialysis membrane, which of the following diffuse(s) into the bloodstream?
bicarbonate ions
Which of the following substances is not normally found in filtrate?
blood cells and large particles
Which factor controlling glomerular filtration rate (GFR) is usually 0 mm Hg under normal circumstances
capsular colloid osmotic pressure
Which solute did NOT appear in the filtrate using the 200 MWCO membrane?
charcoal
Variable secretion of potassium and hydrogen ions is a specific function of which renal structure?
collecting system
Secretion of ADH would _______
decrease in urine output
Contraction of which structure compresses the urinary bladder and expels its contents into the urethra?
detrusor muscle
Which event does not occur when the normal GFR is decreased?
dilation of efferent arterioles
Where does the ureter penetrate the kidney?
hilum
What is(are) the driving force(s) for filtration in the nephron?
hydrostatic pressure gradients and osmotic pressure gradients
ADH is produced in the _______.
hypothalamus
Filtrate flow through the renal tubule increases when glomerular filtration rate
increases
When filtrate flow through the renal tubule increases, the concentration of sodium chloride remaining in the filtrate
increases
Which of the following would decrease glomerular filtration rate?
increasing the efferent arteriole radius and/or decreasing the afferent arteriole radius
The reabsorption of water and solutes _______.
is passive, depends on concentration gradients and is into the peritubular capillaries
What is the osmolarity of the filtrate at the end of the proximal tubule?
isotonic - 300 mOsm
Antidiuretic hormone (ADH), which regulates urine concentration and dilution, is __________.
lowest before Max exercises
The ______ control(s) capillary diameter and the rate of capillary blood flow.
mesangial cells
The ______ collects the urine produced by a single kidney lobe.
minor calyx
Which structure reabsorbs 25 percent of the water in the nephron?
nephron loop
If the osmotic pressure in the glomerular capillaries increased from 28 mm Hg to 35 mm Hg, would net filtration increase or decrease?
net filtration would decrease
What is the limiting factor for the reabsorption of most actively transported solutes in the proximal tubule?
number of transport carriers in the luminal membrane
Metabolic complications of the urinary system associated with diabetes result in:
polyuria
When the pH of body fluids decreases, which of the following are secreted in exchange for sodium ions reabsorbed in the distal convoluted tubule?
potassium ions
Which metabolite(s) or nutrient(s) is/are not present in normal urine?
proteins
In which portion of the nephron and collecting system does the most reabsorption occur?
proximal convoluted tubule
During strenuous exercise, Max's body produces lactic acid and his blood pH begins to decline. His kidneys go to work to preserve acid-base balance by doing all of the following EXCEPT __________.
reabsorbing hydrogen
When filtrate flow through the renal tubule increases, the macula densa responds by releasing vasoconstrictors.
releasing
Where does the kidney filter the blood?
renal corpuscle
What are the two main parts of the nephron?
renal corpuscle and renal tubule
Where are the renal columns located?
renal medulla
In this activity, the drain beaker (second beaker in the flow) simulates the _______.
renal vein
The active transport of which ion out of proximal convoluted tubule cells causes the reabsorption of both water and solutes?
sodium
The urethral lining consists of:
stratified squamous epithelium near the external urethral orifice.
With the valve between the collecting duct and the urinary bladder closed and with the pressure increased, ______
the glomerular filtration rate increased and the glomerular pressure increased
With ADH added but in the absence of aldosterone, _______.
the potassium concentration increased and urine volume decreased
The filtrate produced at the renal corpuscle has:
the same osmotic concentration as plasma.
The decreased intracellular concentration of sodium in tubular cells during active transport is caused by which of the following mechanisms?
the sodium-potassium ATPase pump in the basolateral membrane
Which nitrogenous waste has the lowest concentration (mg/dL) in normal urine?
uric acid
When ADH is present in the filtrate, _______.
urine concentration increases
Which of the following should NOT be found in the filtrate in the Bowman's capsule?
white blood cells
The urine was the most concentrated ______
with both ADH and aldosterone
Which of the following is required for filtration?
Both a membrane and a hydrostatic pressure gradient are required.
Which of the following resulted in an increase in the filtration rate?
Both increasing the pore size and increasing the pressure above the beaker are correct.
Glucose is reabsorbed _______.
All of the above are correct
The addition of aldosterone _______.
decreased urine volume
Given the correlation between urine color and urine concentration, which of the following statements is true about Max's urine?
Max's urine is most dilute before exercise.
Where does filtration of the blood occur within the kidneys?
Renal cortex
Which nervous system structure(s) inhibits micturition by relaxing the detrusor and contracting the internal urethral sphincter?
Stretch receptor impulses activate sympathetic outflow.
In which region of the nephron is tubular fluid first formed?
proximal convoluted tubule
Interstitial fluid is located in the _______.
spaces surrounding the kidney tubule
Which structure of the kidney functions to reabsorb nutrients from the filtrate?
the proximal convoluted tubule Submit
When someone's blood pressure rises slightly, the function of their urinary system will probably most immediately change in which of the following ways?
GFR will rise
What is the function of countercurrent multiplication?
To create a concentration gradient in the renal medulla that permits the production of concentrated urine.
The ureter, blood vessels, and nerves penetrate the kidney on its medial surface.
True
The secretion of ADH is directly stimulated by _______.
a change in body fluid osmolarity
Which of the following is not a general characteristic of normal urine?
a volume of 100 to 250 mL/day
What mechanism is used to adjust the osmotic concentration of tubular fluid in the DCT and collecting system?
active transport
Which blood vessel(s) deliver(s) blood to the glomerulus?
afferent arteriole
Which of the following describes the order in which blood flows through the nephron?
afferent arteriole, glomerulus, efferent arteriole
Increasing the pressure above the beaker is analogous to _______
an increase in blood pressure
At which concentration of glucose carriers was the glucose concentration reduced to zero?
400
What is the normal range for glomerular filtration rate?
80 - 140 ml/min
Max needs to drink more water before exercise to avoid dehydration.
False
The fibrous capsule is a layer of adipose tissue that surrounds the kidney.
False
The medullary pyramids contain collecting tubules (ducts) that travel towards the renal cortex, carrying urine to exit the kidney.
False
Max is curious about the protein content of his urine. Which of these statements provides an accurate basis for Tracey's response, explaining normal conditions?
Few proteins are small enough to pass through the glomerular membrane, but the few that do are reabsorbed. So, proteins are not usually present in urine.
Name the strong transparent covering that encases the kidney.
Fibrous capsule
The pressure in the left source beaker simulates _______.
blood pressure
In this activity, we will explore the effect of _______.
blood pressure on glomerular filtration rate
Which renal structure begins in the renal cortex and carries tubular fluid through the osmotic gradient in the renal medulla?
collecting duct
What is the function of the renal pelvis?
collects newly formed urine
When blood pressure increases, what changes can occur to maintain glomerular filtration rate?
constriction of the afferent arteriole and dilation of the efferent arteriole
When filtrate flow through the renal tubule increases, reabsorption of sodium chloride by the tubule
decreases
Which of the following resulted in an increase in glomerular filtration rate?
decreasing the efferent arteriole diameter and increasing the afferent arteriole diameter
As the number of glucose carriers increased, the concentration of glucose in the _______.
distal tubule decreased and bladder decreased
The nephron loops of juxtamedullary nephrons have an important function that other parts of the nephron do not share. What is this function?
establishing the concentration gradient in the renal medulla
Which of the following is NOT a function of the kidneys?
exchange of oxygen and carbon dioxide with the tissues
Which structure is composed of a layer of collagen fibers that covers the entire outer surface of the kidney?
fibrous capsule
Which transport mechanism(s) results from blood pressure that forces water and solutes across the membranes of the glomerular capillaries and into the capsular space?
filtration
Altering the radii of the afferent and efferent arterioles provides for _______.
glomerular filtration rate homeostasis and glomerular hydrostatic pressure homeostasis
When the beaker pressure was lowered, which of the following decreased?
glomerular pressure, glomerular filtration rate and urine volume
The functions of the nephron include all of the following EXCEPT ______
glomerular secretion
what is the name for the "ball" of capillaries found in the renal corpuscle?
glomerulus
Which structures form the filtration membrane in the nephron?
glomerulus and the glomerular capsule
When the glucose transport maximum is reached, _______.
glucose is excreted in the urine and not all of the glucose is reabsorbed
What is the primary driving force (pressure) that produces glomerular filtration?
hydrostatic pressure of blood (blood pressure)
Which of the following resulted in a decrease in glomerular capillary pressure?
increasing the efferent arteriole diameter and decreasing the afferent arteriole diameter
Because the alteration of the afferent or efferent arteriole occurs within the nephron, we refer to this mechanism as _______
intrinsic
Which substance would be found in higher concentration if the membrane were damaged?
protein
Glucose reabsorption occurs in the _______.
proximal convoluted tubule
Which structure filters the blood
renal corpuscle
Formation of angiotensin I is triggered by ______.
renin
What is the function of the vasa recta?
to collect and transport water and solutes within the renal medulla in association with the juxtamedullary nephron
Most solutes that are reabsorbed in the proximal convoluted tubule use which of the following pathways?
transcellular
With the valve between the collecting duct and the urinary bladder closed, _______.
urine volume was zero
When filtrate flow through the renal tubule increases, the afferent arteriole responds by
vasoconstricting
Neural responses triggered by angiotensin II stimulate the release of ______
ADH
Antidiuretic hormone (ADH) regulates the formation of concentrated or dilute urine. In which time period is Max's body secreting its highest amount of ADH? Explain your answer.
ADH is going to be highest when the body is most dehydrated. In Max's case, this is right after his 2-hour run. During his run, Max loses water via sweat and exhalation, and doesn't effectively replace it. The osmolality of his blood increases, signaling the posterior pituitary to release ADH. ADH targets the principle cells in the collecting ducts of the kidney tubules, causing them to increase reabsorption of water from the filtrate. This negative feedback mechanism attempts to conserve water in order to decrease blood osmolality and restore body fluid homeostasis.
Max's regular exercise regimen has reduced his high blood pressure, allowing him to achieve normal blood pressure on a single antihypertensive medication. The medication he takes is called an angiotensin converting enzyme inhibitor, or ACE inhibitor, which blocks the activation of angiotensin II. Describe at least two mechanisms by which angiotensin II targets the kidneys to increase extracellular fluid volume and, therefore, increase blood pressure.
Angiotensin II directly signals the renal tubules to reabsorb sodium. Where sodium goes, water follows by osmosis, causing blood volume and pressure to increase. Angiotensin II signals the release of ADH from the posterior pituitary. ADH acts on the principle cells of the collecting ducts to cause reabsorption of water from the filtrate into the blood. Blood volume and pressure are increased. Angiotensin II is a potent vasoconstrictor, which leads to a decline in peritubular capillary hydrostatic pressure and more fluid reabsorption. Blood volume and pressure are increased. Angiotensin II prompts the release of aldosterone from the adrenal medulla. Aldosterone stimulates renal tubules to reabsorb sodium (with water following) and this leads to an increase in blood volume and pressure. Angiotensin II stimulates the glomerular mesangial cells to contract and reduce glomerular filtration rates. Less filtrate is produced, less fluid is lost in urine, and blood volume and pressure are increased. Angiotensin II triggers thirst by acting at the hypothalamus. This increases blood volume and blood pressure.
When the macula densa detects an increase in NaCl concentration in the renal filtrate, what happens to the glomerular filtration rate (GFR)?
GFR decreases.
As the pressure in the beaker was increased, which of the following occurred?
Glomerular filtration rate increased, and urine volume increased.
Tracey had been slightly concerned about the trace glucose that was found in Max's urine six hours after his exercise until she discovered that he had eaten an entire large pizza an hour before the urinalysis. Explain why glucose might show up in Max's urine after a particularly heavy meal.
Glucose passes easily through the glomerular filtration membrane, and normally 100% of it is reabsorbed in the proximal convoluted tubule (PCT). The reabsorption of glucose is accomplished by secondary active transport and requires a transport protein in the membrane to facilitate the movement of glucose across the membrane. Typically, there are more than enough of these transport proteins, but they do have an upper limit beyond which no more glucose can be transported. This is called the transport maximum (Tm) for glucose. Generally, the Tm for glucose is not reached until blood levels of glucose exceed 180 mg/dL, which is known as the renal threshold. The most common cause of hyperglycemia (high blood glucose) is diabetes mellitus. So, if the renal threshold is exceeded for glucose in the PCT, it will "spill" into the filtrate and be eliminated in urine. Without further testing, it's unknown whether Max has a lower-than-normal renal threshold for glucose, or has exceeded the normal renal threshold of 180 mg/dL with his heavy meal.
Lactic acid accumulation can be a consequence of intense exercise. Tracey notes that Max's kidneys are working to defend his body against acidosis. How can she tell? Describe this mechanism.
Max's pH is more acidic right after his run. This is evidence of a higher hydrogen concentration in urine. When pH drops, the tubule cells secrete hydrogen into the filtrate, allowing it to be lost in urine. They also reabsorb bicarbonate (a base) to help buffer the body fluids. The result is a restoration of normal pH.
Based on Max's urinalysis data, should he drink more water prior to exercise to ensure that he doesn't dehydrate during intense activity? Explain your answer.
Max's urine is already extremely dilute before exercise, indicating he is probably well hydrated. If he were to drink more, then he would simply end up with a full bladder during his run (the kidneys would eliminate the excess water). Better advice would be to drink more strategically during his run. For instance, when he is doing his training runs, Max could take a drink every 15 minutes (more if he is sweating heavily) and practice different drinking regimens when he trains until he finds one that keeps him hydrated but does not require him to stop to urinate during his run.
If the osmotic pressure in the glomerular capillaries increased from 28 mmHg to 35 mmHg due to dehydration, would net filtration increase or decrease?
Net filtration would decrease.
Tracey explains to Max that his transiently elevated blood glucose leads to "spilling" of glucose into his urine. Why does this happen?
Reabsorption of glucose is limited by transport proteins.
Which structure is found separating the renal pyramids?
Renal columns
Which of the following regions of the kidney is in contact with the fibrous capsule?
Renal cortex
Which region of the kidney is the most superficial?
Renal cortex
A major calyx is a component of which of the following anatomical structures?
Renal pelvis
The presence or absence of a solute in the filtrate depends on _______.
The molecular weight and size of the solute as well as the MWCO and pore size of the membrane
Tracey knows that proteinuria (protein in the urine) after intense exercise is physiological (normal). However, protein is typically not present in urine. Why is that?
The protein in urine after exercise could come from the metabolism of muscle and blood that come with increased exercise, these proteins end up in the blood, are filtered into the urine and secreted out of the body. Without exercise, this metabolism of muscle and blood cells does not normally occur, so they are not picked up in the urine sample.
Based on the urine color and specific gravity, what might Tracey conclude about the hydration status of Max's body at the three different times?
When Max's urine is pale with a low specific gravity, his body is likely to be well hydrated; the kidneys are reabsorbing less water, allowing it to be eliminated in urine. When his urine is dark yellow with a higher specific gravity, his kidneys are concentrating urine and reabsorbing more water in an attempt to maintain body fluid homeostasis (defend plasma osmolality). Dehydration will trigger this response. The yellow urine signals dehydration; the corresponding high-normal specific gravity is likely due to the small amount of glucose in the urine.
When the efferent arteriole constricts, _______.
the back pressure in the Bowman's capsule increases
Glucose is transported _______.
through the basolateral membrane by facilitated diffusion