A&P Chapter 24

The female urethra provides passages a passage for *blank* where as the male urethra provides passageway for *blank* and *blank*

urine; urine and semen

24.6.5. What three factors allow the kidney to produce and maintain the medullary osmotic gradient?

1. A countercurrent multiplier system in the nephron loops of the juxtamedullary nephrons 2. The recycling of urea in the medullary collecting ducts 3. A countercurrent exchanger in the vasa recta

24.1.2. What are the basic functions of the kidneys?

1. Filter blood to remove metabolic wastes via urine 2. Regulate fluid and electrolyte balance by regulating osmolarity, blood solute concentration, conserving or eliminating water and electrolytes 3. Regulate acid-base balance and blood pH by conserving or eliminating hydrogen and bicarbonate ions. 4. Directly influence BP by controlling blood volume and secreting an enzyme that influences blood volume and peripheral resistance 5. regulate red blood cell production, erythropoiesis, by hormone erythropoietin

24.2.2. What are the three regions of the kidney, and how do they differ structurally?

1. Renal cortex - outermost, rich blood supply, renal columns, urine forming part of kidney 2. Renal medulla - middle, renal pyramids and renal columns, urine forming part of kidney 3. Renal Pelvis - innermost, urine draining part of kidney, chamber

24.3.1. What happens during glomerular filtration?

1. The glomerular capillary membranes filter blood selectively based on size so cells and large proteins are not filtered and remain in the circulating blood 2. Smaller substances such as water, electrolytes (Na and K ions), acids and bases (H and bicarbonate ions), organic molecules, and metabolic waste exit the blood to enter the capsular space as filtrate or tubular fluid.

24.4.5. Which three pressures combine to determine the net filtration pressure? Which pressure(s) promote filtration, and which oppose filtration?

1. The glomerular hydrostatic pressure - determined mostly by systemic blood pressure, favors filtration 2. The glomerular colloid osmotic pressure - created mostly by albumin, opposes filtration 3. Capsular hydrostatic pressure - generated as the capsular space rapidly fills with new filtrate, opposes filtration

24.5.1. What are the two routes of reabsorption and secretion?

1. The paracellular route - substances pass between adjacent tubule cells, mostly in proximal tubule; passive movement. 2. The transcellular route - substances such as glucose and amino acids move through tubule cells; mostly active. All secretion is always active always via transcellular route.

24.4.8. What are the basic steps of the renin-angiotensin-aldosterone system?

1. When blood pressure drops so does the GFR, and the reduction in blood flow through the afferent arteriole triggers the JG cells to release renin into the bloodstream. 2. Renin converts angiotensinogen to angiotensin I that can be further converted to the more active form, angiotensin II, by the angiotensin converting enzyme (ACE) produced by the endothelial cells in the lungs. 3. Angiotensin II promotes vasoconstriction of efferent arterioles and systemic blood vessels, promotes reabsorption of Na ions, Cl ions, and water from the proximal tubule; promotes aldosterone release further promoting sodium and water reabsorption; and increases thirst, all of which increase systemic blood pressure and subsequently GFR.

24.4.1. Ms. Douglas has advanced liver disease; because her liver is no longer able to produce plasma proteins, her colloid osmotic pressure has decreased. Predict the effects that his loss of pressure will have on the net filtration pressure and GFR in her nephrons.

A decrease in colloid osmotic pressure will decrease the force that retains water in the blood in the glomerulus. As a result, the net filtration pressure will increase in favor of filtration, and more filtrate will be produced.

24.4.4. What is the GFR?

The glomerular filtration rate is the amount of filtrate formed by both kidneys in 1 minute

Ms. Douglas has advanced liver disease; because her liver is no longer able to produce plasma proteins, her colloid osmotic pressure has decreased. Predict the effects that this loss of pressure will have one the net filtration pressure and the GFR in her nephrons

A decrease in colloid osmotic pressure will decrease the force the retains water in the blood in the glomerulus. As a result, the net filtration pressure will increase in favor of filtration, and more filtrate will be produce

How would a spinal cord injury about the level of S1-S2 affect maturation in that patient? How would the situation change if the injury were below S1-S2

A spinal card injury above S1-S2 would prevent voluntary control of the micturition, as the impulses would be unable to reach the micturition center in the pons. An injury below S1-S2 could damage the neurons in the involuntary pathway of the micturition reflex. This could leas urinary retention, because the signals that trigger the emptying of the urinary bladder would be interrupted

24.9.2. How would a spinal cord injury above the level of S1-S2 affect micturition in that patient? How would the situation change if the injury were below S1-S2?

A spinal cord injury above S1-S2 would prevent voluntary control of micturition, as the impulses would be unable to reach the micturition center in the pons. An injury below S1-S2 could damage the neurons in the involuntary pathway of the micturition reflex. This could lead to urinary retention, because the signals that trigger the emptying of the bladder would be interrupted.

Dilute produced when crease levels of *blank* are secreted

ADH

24.5.8. How does ADH influence water reabsorption?? In which parts of the nephron and collecting system does the ADH act?

ADH is made by the hypothalamus and secreted by the posterior pituitary that causes water reabsorption in the distal tubule and cortical collecting duct -> reduces urine output.

24.4.10. What are the effects of ANP on the GFR?

ANP is a hormone released by heart cells in the atria in response to increasing fluid volume that lowers blood volume and blood pressure to reduce the workload of the heart.

24.9.1. What are the three tissue layers of the organs of the urinary tract?

Adventitia, muscularis, and mucosa.

24.5.7. How does aldosterone impact reabsorption and secretion in the late distal tubule and cortical collecting duct?

Aldosterone increases reabsorption of sodium ions from the filtrate and secretion of potassium ions into the filtrate. It also causes indirect water and Cl- ions reabsorption, because water and Cl- ions follow Na+ ions. Aldosterone will also cause loss of H+ ions.

Drugs that treat hypertension, or high blood pressure, have the following actions. Discuss the specific effect that each drug will have on the kidney: Blocking the action of aldosterone on the kidney

Aldosterone promotes the retention of Na+ and water in the late distal tubule and cortical collecting duct. Adverse effects of blocking aldosterone including high plasma K+ and acidosis. as aldosterone normally promotes the secretion of K+ and H+

Predict the effects the following scenarios would have on glomerular filtration: having excess protein in the blood, increasing colloid osmotic pressure

An increase in colloid osmotic pressure will increase the forces opposing filtration in the glomerulus, so the GFR will decrease

Drugs that treat hypertension, or high blood pressure, have the following actions. Discuss the specific effect that each drug will have on the kidney: Blocking the receptor for angiotensin II on blood vessels in the renal tubule cells

Ang-II normally causes constriction of the efferent arteriole and systemic blood vessels. If you block the receptors for Ang-II on the vessels of the kidney, you could potentially dilate the efferent arteriole and lower the GFR

The enzyme *blank* converts angiotensin I to angiotensin II

Angiotensin- converting enzyme

24.2.6. What are the two components of the renal corpuscle?

The glomerulus and the glomerular capsule.

24.2.2. Predict the potential effects of abnormally narrow renal arteries, a condition called renal artery stenosis, on the ability of the kidneys to carry out their functions.

Anything that decreases the blood flow to the kidneys will lower the rate of filtration of fluid from the blood into the nephrons and therefore decrease the regulation of fluid, electrolyte, and acid-base balance performed by the kidneys.

Predict the potential effects of abnormally narrow renal arteries, a condition called renal artery stenosis on the ability of the kidney to carry out their function

Anything that decreases the blood flow to the kidneys will lower the rate of filtration of fluid from the blood into the nephrons and therefore decrease the regulation of fluid, electrolytes, and acid- base balance performed by the kidney

Certain diuretics block the effects of carbonic anhydrase in the proximal tubule. Predict the effects these drugs would have on pH of the blood. How might the kidneys compensate for this

Blocking carbonic anhydrase will result in the reabsorption of fewer sodium and bicarbonate ions. This will lead to a decrease pH of the blood, as fewer bicarbonate ions will be resent to buffer the blood. The resulting acidosis will cause the kidneys to increase secretion of hydrogen ions and retain bicarbonate ions from the distal tubule

24.7.2. Certain diuretics block the effects of carbonic anhydrase in the proximal tubule. Predict the effects these drug would have on the pH of the blood. How might the kidneys compensate for this?

Blocking carbonic anhydrase will result in the reabsorption of fewer sodium and bicarbonate ions. This will lead to a decreased pH of the blood. The resulting acidosis will cause the kidneys to increase secretion of hydrogen ions and retain bicarbonate ions from the distal tubule.

Which of the following is not a physiological process carried out by the kidneys?

Blood pressure regulation, tubular reabsorption, tubular secretion, and glomerular filtration

24.8.2. What are its normal characteristics?

Color - yellow, depending on the amount of urochrome odor pH - around 6.0 Specific gravity - around 1.001

The sympathetic nervous system *blank* the blood vessel supplying the kidney to the *blank* the GFR

Constricts; reduce

Dietary supplementation with creatine phosphate is popular among athletes for its supposed performance- enhancing effects. What effects would creatine phosphate supplementation have on the amount of creatinine that the kidneys must excrete?

Creatine phosphate is metabolized to creatinine, and so an increase in consumption of creatine will lead to an increased amount of creatinine in the blood. This will increase the workload of the kidneys, as they must excrete the excess creatinine

24.8.2. Dietary supplementation with creatine phosphate is popular among athletes for its supposed performance-enhancing effects. What effect would creatine phosphate supplementation have on the amount of creatinine in the blood, and therefore the amount of creatinine that the kidneys must excrete?

Creatine phosphate is metabolized to creatinine, and so an increase in consumption of creatine will lead to an increased amount of creatinine in the blood. This will increase the workload of the kidneys, as they must excrete the excess creatinine.

24.4.1. What are the three components of the filtration membrane?

Deep to superficial, the fenestrated glomerular capillary endothelial cells, a basal lamina, and the podocytes. These three layers collectively create a barrier.

When the GFR decreases, the macula dense releases chemicals to *blank* afferent arteriole

Dilate

24.4.6. What happens to the GFR when the afferent arteriole constricts? What happens to the GFR when it dilates?

Dilating - increases GFR Constricting - decreases GFR

24.6.2. What are dilute urine and concentrated urine?

Dilute urine - less than 300 mOsm, less water is absorbed in the late distal tubule and collecting duct. Concentrated - greater than 300 mOsm, more water is reabsorbed in the late distal tubule and collecting duct.

Mr. Adams is taking an ACE inhibitor and an angiotensin receptor blocker, both drugs that block RAAS, for his high blood pressure. He complaisant hat when he tries to engage in physical activity, he feels faint. He is asked to exercise on a treadmill, and his blood pressure remains very low when he exercise, rather than rising with his levels of physical activity. Explain how his medication could be causing his problem.

Drugs that block the RAAS will inhibit overall vasoconstriction, and this can reduce the vasoconstriction that normally occurs with physical activity. With out normal vasoconstriction, the blood pressure remains low, even when it would normally rise.

24.4.3. Mr. Adams is taking an ACE inhibitor and an angiotensin-receptor blocker, both drugs that block the RAAS, for his high blood pressure. He complains that when he tries to engage in physical activity, he feels faint. He is asked to exercise on a treadmill, and his blood pressure remains very low when he exercises, rather than rising with his level of physical activity. Explain how his medication could be causing his current problem.

Drugs that block the RAAS will inhibit overall vasoconstriction, and this can reduce the vasoconstriction that normally occurs with physical activity. Without this normal vasoconstriction, the blood pressure remains low, even when it would normally rise.

24.5.2. What are the three types of transport processes that involve carrier proteins in the renal tubule and collecting system?

Facilitated diffusion, primary active transport, and secondary active transport.

24.6.4. How do the kidneys produce dilute urine?

Facultative water reabsorption is turned off as ADH hormone is suppressed, rendering late distal tubule and collecting duct impermeable to water.

24.9.3. How does the urethra differ structurally and functionally in males and females?

Female - urethra is shorter (about 4 cm), opens at the external urethral orifice between the vagina and clitoris, serves primarily as an exit for urine. Male - longer urethra (about 20 cm), consists of the prostatic region, membranous region, and the spongy urethra region. Is an exit for urine and sperm.

24.2.7. Trace the pathway filtrate takes through the nephron and collecting system from the capsular space to the papillary duct.

Fig. 24.5 p 952

24.4.2. What is the function of the filtration membrane?

Filter blood selectively based on size so blood cells and platelets, and large proteins are not filtered and remain in the circulating blood.

24.5.2. What effect would this toxin have on the reabsorption of glucose and bicarbonate ions?

Glucose molecules are reabsorbed with sodium ions as a result of secondary active transport. Bicarbonate ions are reabsorbed as a result of the Na+/H+ antiporter in the proximal tubule. If all sodium ion reabsorption were blocked, the glucose/sodium ion cotransporter and Na+/H+ antiporter would not function, and high amounts of glucose and bicarbonate ions would appear in the urine.

You discover a new toxin that blocks the reabsorption of all sodium ions from the proximal tubule. What effect would this toxin have on the reabsorption of glucose and bicarbonate ions?

Glucose molecules are reabsorbed with sodium ions as a result of the secondary active transport. Bicarbonate ions are reabsorbed as a result of the Na+/H+ anti-porter in the proximal tubule. If all sodium ion reabsorption were blocked, the glucose/ sodium ion cotransporter and Na+/H+ antiporter would not function. and high amounts of glucose and urine would not appear in the urine.

Predict the effects the following scenarios would have on glomerular filtration: Having high arteriole blood pressure

Hypertension will increase the glomerular hydrostatic pressure and increase the force favoring filtration, leading to an increase in the GFR. Note the tubuloglomerular feedback and myogenic mechanism will compensate for this

Respiratory condition can cause chronic hypoventilation that leads to a decrease of blood pH. Predict how the kidneys will respond to this change in pH.

Hypoventilation will lead to acidosis, which causes the kidneys to increase their secretion of hydrogen ions and increase the reabsorption of bicarbonate ions

24.5.3. Respiratory conditions can cause chronic hypoventilation that leads to a decreased blood pH. Predict how the kidneys will respond to this change in pH.

Hypoventilation will lead to acidosis, which causes the kidneys to increase their secretion of hydrogen ions and increase the reabsorption of bicarbonate ions.

Drugs called loop diuretics block the Na+/K+/2Cl- symporters in the thick ascending limb of the nephron loops. b. Predict what might happen if the drug instead had the opposite effect- it caused more sodium and chloride ions to be reabsorbed into the medullary interstitial fluid

If the drug instead stimulated the Na+/K+/2Cl- pumps, a steeper gradient in the renal medulla would be created for water reabsorption. This would cause a person to produce more concentrated urine and retain more water, possibly leading to overhydration

Drugs that would lower blood pressure

If you block aldosterone, you also block sodium ion in the water reabsorption which reduces blood volume and blood pressure. Drugs that block angiotensin-II receptors on blood vessels will lower blood pressure by allowing for systemic vasodilation. The result of blocking pumps in the nephron loop reducing the medullary osmotic gradient will be production of a larger volume of dilute urine, which decreases blood volume and blood pressure

Generally, angiotensin II *blank* systemic blood pressure while *blank* the GFR

Increases; maintaining

24.4.9. What are the effects of the RAAS on the GFR?

It maintains systemic blood pressure primarily and GFR secondarily.

24.6.1. How does the concentration of the filtrate change as it passes through the renal tubule and collecting system?

Look at notes.

24.9.4. What are the steps of the micturition reflex?

Look at notes.

The process by which urine is eliminated is called *blank*, and it is mediated by reflexes involving the *blank* nervous system

Micturition; parasympathetic

Mr. Wu is a patient with kidney disease who presents to your clinic for monitoring. You notice on his chart that his GFR was estimated through inulin administration to be about 35ml/min. What does this tell you about the health of his kidneys? Mr. Wu is taking medication that is normally excreted from the body in the urine. You order blood work and find that the concentration of this medication in his plasma is higher than normal. How does his decreased GFR explain the elevated level of medication in his plasma?

Mr. Wu's GFR, at 35ml/min, is much lower than normal, which m Eans he is in renal failure and inadequate amounts of blood is being filtered each minute. The plasma concentration of the drugs are higher than expected, therefore, because the drug is not being eliminated as it should by the kidneys

24.6.6. How is concentrated urine produced?

Osmoreceptors in hypothalamus monitor concentration of solutes in blood. When solute concentration is high ADH is released -> aquaporins (water channels) are inserted into the cell membranes of cells in the distal tubule and collecting duct -> water reabsorption continues from the medullary collecting duct into interstitial fluid -> vasa recta.

1. What are the four main organs of the urinary system?

The four main organs of the urinary system are the kidneys, ureters, urinary bladder, and urethra.

24.1.1. Inflammation of the peritoneal membranes, or peritonitis, can cause dysfunction of multiple organs in the abdominal cavity. Would you expect peritonitis to affect the kidneys? Explain.

Peritonitis would be unlikely to impact the kidneys, as they are retroperitoneal, or located posterior to the peritoneal membrane.

The GFR may be estimated by measuring the rate at which certain substance are removed from the blood, which is known as

Renal clearance

24.8.3. What is renal clearance and what is it used to estimate?

Renal clearance is a measurement of the rate at which the kidneys remove a substance from the blood. It can be used to estimate the glomerular filtration rate; both measure in millimeters of plasma per minute.

24.9.1. Predict what would happen if the epithelium of the urinary tract were made of simple squamous epithelium instead of transitional epithelium.

Simple squamous epithelium is very thin and would not protect the underlying connective and muscle tissue of the ureters and urinary bladder. In addition, the simple squamous cells would not be as able to change shape with the changing size of these structures, and would be more prone to tears and other structural disruptions.

Drugs called loop diuretics block the Na+/K+/2Cl- symporters in the thick ascending limb of the nephron loops. a. Predict the effect these drugs will have on the gradient in the renal medulla, and the resulting effect on water reabsorption from the medullary collection system. How will this impact urine volume?

Since less sodium chloride is piped into the interstitial fluid, the gradient for water reabsorption from the medullary collecting system will be decrease. This will reduce the volume of water reabsorbed and thus increase urine volume

24.4.3. Which substances are found in the filtrate?

Smaller substances such as water, electrolytes (Na and K ions), acids and bases (H and bicarbonate ions), organic molecules and metabolic wastes.

Which of the following substances would pass through the filtration membrane to become a part of the filtrate under normal circumstances

Sodium ions, glucose, amino acids, and urea

Deana is a 4 year old girl with a rare genetic defect that causes the Na+/ glucose symporters in the proximal tubule to reabsorb fewer glucose and sodium ions than normal. Predict the effects this defect will have on the composition and volume of Deana's urine. Explain why you would expect to see increase activity to the tubuloglomerular feedback and the renin-angiotensin-alsosterone system in Deana's kidneys

Sodium reabsorption in the proximal tubule drives the reabsorption of many solutes, so the concentration of these solutes, including glucose and many electrolytes, would increase in the urine. Sodium ions also drive the reabsorption of water by osmosis, and therefore the volume of urine would increase. The presence of sodium ions in the filtrate would trigger the macula dense to relate chemical that cause construction of the afferent arteriole and decrease in the GFR. The macula dense will also trigger the release of renin from JG cells, which activates the RAAS and culminates in systemic vasoconstriction and other effects of Ang-II

Certain drugs that treat high blood pressure cause vasodilation of systemic arteries and arterioles, including those in the kidneys. What effect would those drugs have on the GFR? How would the myogenic mechanism and the tubular feed back respond to this change in GFR?

Such drugs would increase the GFR temporarily by increasing the glomerular hydrostatic pressure due to the dilation of renal arteries and afferent arterioles. However, these changes would be countered very rapidly by the myogenic mechanism and tubuloglomerular feedback, both of which would trigger constriction of the afferent arteriole to decrease GFR

24.4.2. Certain drugs that treat high blood pressure cause vasodilation of systemic arteries and arterioles, including those in the kidneys. What effect would these drugs have on the GFR? How would the myogenic mechanism and tubuloglomerular feedback respond to this change in the GFR?

Such drugs would increase the GFR temporarily by increasing the glomerular hydrostatic pressure due to the dilation of renal arteries and afferent arterioles. However, these changes would be countered very rapidly by the myogenic mechanism and tubuloglomerular feedback, both of which would trigger constriction of the afferent arterioles to decrease GFR.

Which of the following is true about GFR

The GFR average is about 120 ml/min, the GFR increases when the afferent arteriole dilates, the GFR decreases when the afferent arteriole constricts

Which of the following is false about GFR

The GFR decreases when the efferent arteriole constricts

Which of the following conditions does not contribute to the creation and/or maintenance of the medullary osmotic gradient

The countercurrent multiplier nephron loop of cortical nephrons

Glomerulonephritis, or inflammation of the glomerulus, result in the excessively leaky glomerular capillaries and damaged glomeruli. The damage and destroyed glomeruli cause the GFR to decrease. Which compensatory glomeruli mechanism would you expect to be triggered, and what effects would they have?

The decrease GFR would tigger the RAAS and Bl feedback, both of which would lead to increased glomerular hydrostatic pressure and a slightly increase in the GFR

24.7.1. Glomerulonephritis, or inflammation of the glomerulus, results in excessively leaky glomerular capillaries and damaged glomeruli. The damaged and destroyed glomeruli cause the GFR to decrease. Which compensatory mechanisms would you expect to be triggered, and what effects would they have.

The decreased GFR would trigger the RAAS and tubuloglomerular feedback, both of which would lead to increase glomerular hydrostatic pressure and a slight increase in the GFR.

24.5.5. How do the permeabilities of the two limbs of the nephron loop differ?

The descending lib is freely permeable to water, whereas the ascending limb is impermeable to water but can transport NaCl into tubule cells with use of Na/K/Cl symporters.

You discover a new toxin that blocks the reabsorption of all sodium ions from the proximal tubule. What effects would this drug have on the reabsorption od water and other electrolytes from this tubule?

The drug would significantly decrease the amount of water and certain electrolytes reabsorbed from the proximal tubule. If fewer sodium ions are reabsorbed, there will be a smaller electrical gradient for reabsorbing chloride, a smaller osmotic gradient for reabsorbing water, and therefore a smaller concentration gradient for reabsorption of other electrolytes

24.5.1. You discover a new toxin that blocks the reabsorption of all sodium ions from the proximal tubule. What effect would this drug have on the reabsorption of water and other electrolytes from this tubule.

The drug would significantly decrease the amount of water and certain electrolytes reabsorbed from the proximal tubule. If fewer sodium ions are reabsorbed, there will be a smaller electrical gradient for reabsorbing chloride, a smaller osmotic gradient for reabsorbing water, and therefore a smaller concentration gradient for reabsorption of other electrolytes.

5. Describe the structure of the filtration membrane

The filtration membrane consists of a series of three progressively finer filters, including the glomerular endothelial cells, the basal lamina, and the filtration slits of the podocytes.

24.1.1. What are the organs of the urinary system?

The kidneys and the urinary tract, which consists of a pair of ureters, the urinary bladder, and a single urethra.

24.1.2. Explain why a patient with long-term renal failure might have a decreased number of erythrocytes in his or her blood.

The kidneys produce the hormone erythropoietin, which stimulates erythrocyte production. In renal failure, all aspects of kidney function decrease, including production of erythropoietin. The lower levels of the hormone cause decreased rates of erythropoiesis.

Predict the effects of a condition that results in gradual loss of microvilli from the proximal tubule

The microvilli of the proximal tubule increase the surface area available for absorption of water and other solutes. If the number of microvilli decreases, the cells will be unable to reabsorb the same amount of water and solutes. As a result, urine volume would increase and solutes such as glucose and amino acids would be found in the urine

24.2.1. Predict the effects of a condition that results in gradual loss of microvilli from the proximal tubule.

The microvilli of the proximal tubule increase the surface area available for absorption of water and other solutes. If the number of microvilli decreases, the cells will be unable to reabsorb the same amount of water and solutes. As a result, urine volume would increase and solutes such as glucose and amino acids would be found in the urine.

24.2.3. What is the functional unit of the kidney?

The nephron - found in cortex and medulla of kidneys, globe shaped renal corpuscle at one end and long renal tubule

24.3.2. How do tubular reabsorption and tubular secretion differ?

The process of tubular reabsorption is to modify the filtrate as it flows through the tubules, whereas the process of tubular secretion is where substances are added into the filtrate from the peritubular capillaries for excretion from the body.

24.2.1. What are the three connective tissue coverings of the kidney?

The renal fascia, adipose capsule, and renal capsule.

24.10.1. Rory presents with a staghorn calculus, a huge kidney stone that forms in the renal pelvis and extends into the major and minor calyces. Rory's staghorn calculus is preventing urine from draining from his renal pelvis into his ureter. How do you think that his is affecting the GFR of the affected kidney? Why?

The staghorn calculus is causing a "backup" in the kidney by preventing urine from draining from the major and minor calyces into the renal pelvis. The backup is increasing the amount of filtrate in the collecting system and nephron, which in turn increase the amount of filtrate that remains in the capsular space. This increases the capsular hydrostatic pressure, a force that opposes filtration. An increased capsular hydrostatic pressure causes the net filtration pressure to fall, which leads to a drop in the GFR.

Rory presents with a stag horn calculus, a huge kidney stone that forms in the renal pelvis and extends into the major and minor calyces. Rory's stag horn claques is preventing urine from draining urine from his renal pelvis into his ureter. How do you think this is affecting the GFR of the affecting kidney? Why?

The staghorn calculus is causing a "backup" in the kidney by preventing urine from draining from the major and minor calyces not the renal pelvis. The back up is increasing the amount of filtrate in the collecting system and nephron, which intern increases the amount of filtrate that remains in the capsular space. This increases the capsular hydrostatic pressure causes the net filtration pressure to fall, which leads to a drop in the GFR

24.4.11. How does the sympathetic nervous system affect the GFR at both low and high levels of stimulation?

The sympathetic nervous system controls the constriction of afferent arterioles. The effect on GFR depends on the level of stimulation. A low level of stimulation will increase GFR -> more urine production, but a high level of stimulation as happens when blood has been lost in an accident, GFR decreases -> lower urine production.

Drugs that treat hypertension, or high blood pressure, have the following actions. Discuss the specific effect that each drug will have on the kidney: Blocking the Na+/Cl-/2K+ transport pumps in the thick ascending limb of the nephron loop

These pumps are largely responsible for creating the gradient needed for countercurrent multiplication and the production of concentrated urine. Blocking these pumps lead to large volume of dilute urine. However, these drugs also block the reabsorption of K+, which can lead to low plasma K+ concentrations

24.4.7. How does tubuloglomerular feedback affect the GFR?

This autoregulation mechanism involves the macula densa of the distal renal tubule where a negative feedback loop controls pressure in the glomerulus in response to the NaCl concentration of the filtrate. More NaCl in distal tubule -> stimulus for tubuloglomerular system -> constrict -> afferent arteriole -> restrict loss of NaCl and also raise BP.

Predict the effects the following scenarios would have on glomerular filtration:Having low arterial blood pressure

This condition will decrease the glomerular hydrostatic pressure, and therefore decrease the force favoring filtration, leading to a reduced GFR. Note that renin-angiotensin-aldosterone system would compensate somewhat for this, as would tubuloglomerular feedback

The route by which substances are reabsorbed by crossing through the cells of the renal tubule and collecting system known as the:

Transcellular route

Normal urine should have which of the following properties

Translucency and cloudy appearance

24.9.2. What are the functions of the ureters and urinary bladder?

Ureters - empties urine into the urinary bladder Urinary bladder - hollow, distensible organ found on the pelvic cavity floor and held in place by parietal peritoneum. Collapses when empty but becomes pear shaped when full, holding 700-800 mL of urine in males and slightly less in females.

24.5.6. What is reabsorbed from the filtrate in the nephron loop?

Water reabsorbed in the descending limb and NaCl reabsorbed in the ascending limb.

Why must kidneys establish a concentration gradient in the interstitial fluid of the renal medulla in order to produce concentrated urine

Water reabsorption, which is needed to produce concentrated urine, occur by osmosis. Osmosis is the movement of water from a solution with a lower solitude concentration to one with a high solute concentration. So, for osmosis to occur across the medullary collecting ducts, the interstitial fluid must be more concentrated than the filtrate

24.8.1. What is the normal composition of urine?

Water, sodium, potassium, chloride, hydrogen ions, phosphates, sulfates, and metabolic wastes such as urea, creatinine, ammonia, and uric acid. Small amounts of bicarbonate, calcium, and magnesium can also be present. Urochrome -> breakdown product of hemoglobin, giving it yellow color.

24.6.3. Under what condition do the kidneys produce dilute urine?

When the solute concentration of the extracellular fluid is too low because, in other words, it contains too much water.

24.5.4. What is obligatory water reabsorption?

Where sodium ions, glucose, and other organic molecules have already been reabsorbed. Water is "obliged" to follow the reabsorbed substances.

Alcohol inhibits the release of ADH. Predict how this inhibition will influence urine volume and concentration

With lower levels of ADH, less water will be reabsorbed from the distal tubule and collecting system. This will increase urine volume and decrease urine concentration

24.6.1. Alcohol inhibit the release of ADH. Predict how this inhibition will influence urine volume and concentration.

With lower levels of ADH, less water will be reabsorbed from the distal tubule and collecting system. This will increase urine volume and decrease urine concentration.

Metabolic acidosis is a characteristic by a decreased blood pH from the accumulation of metabolic acids. Predict the effects this condition will have on pH in the urine. What effects would you expect the opposite condition, metabolic alkalosis, to have on urine pH?

With metabolic acidosis, you would expect the pH of the urine to be low; however, it will not likely drop below 4.5 irrespective of the degree of acidosis. With metabolic alkalosis, the urine pH will rise as more hydrogen ions are retained and bicarbonate ions are excreted

24.8.1. Metabolic acidosis is characterized by a decreased blood pH from the accumulation of metabolic acids. Predict the effects this condition will have on the pH of urine. What effect would you expect the opposite condition, metabolic alkalosis, to have on the urine pH?

With metabolic acidosis, you would expect the pH of the urine to be low; however, it will not likely drop below 4.5 irrespective of the degree of acidosis. With metabolic alkalosis, the urine pH will rise as more hydrogen ions are retained and bicarbonate ions are excreted.

6. Which of the following substances would pass through the filtration membrane to become part of the filtrate under normal circumstances? (Circle all that apply.) a. Sodium ions b. Albumin c. Glucose d. Erythrocytes e. Leukocytes f. Amino acids g. Urea

a Sodium Ions, c Glucose, f Amino Acids, g Urea

24.5.3. Which substances are reabsorbed from the proximal tubule? Which of these substances are reabsorbed using the sodium ion gradient?

a) sodium, potassium, chloride, sulfate, and phosphate ions. b) Chloride, glucose, amino acids, sulfate, and phosphate (through symporters), HCO3- (via Na-H antiporter)

15. Normal urine should have which of the following properties? Circle all that apply. a. Translucency b. Yellowish pigment c. Cloudy appearance d. pH less than 4.5

a. Translucency b. Yellowish pigment

3. Mark the following statements as true or false. If a statement is false, correct it to make a true statement. a. The kidneys are retroperitoneal and covered by three layers of connective tissue. b. Internally, the kidneys consist of an outer renal medulla, a middle renal pelvis, and an inner renal cortex. c. The first capillary bed of the kidneys is the peritubular capillaries, which are fed by the afferent arteriole and drained by the efferent arteriole. d. Filtrate flows from the renal corpuscle to the distal tubule, the nephron loop, the proximal tubule, and into the collecting system.

a. True b. False: Internally, the kidneys consist of an outer renal cortex, a middle renal medulla, and an inner renal pelvis. c. False: The kidneys' first capillary bed is the glomerulus, which is fed by the afferent arteriole and drained by the efferent arteriole. d. False: Filtrate flows from the renal corpuscle to the proximal tubule, the nephron loop, the distal tubule, and into the collecting system

11. Mark the following statements as true or false. If a statement is false, correct it to make a true statement. a. Sodium ions and glucose are cotransported into the proximal tubule cell by secondary active transport. b. The distal tubule reabsorbs sodium ions and secretes potassium and hydrogen ions in response to ADH. c. Sodium ion reabsorption creates a gradient that helps drive the reabsorption of water and many other solutes from the proximal tubule. d. ADH triggers water reabsorption from the nephron loop. e. Obligatory water reabsorption occurs in the distal tubule and collecting system.

a. True b. False: The distal tubule reabsorbs sodium ions and secretes potassium and hydrogen ions in response to aldosterone. c. True d. False: ADH triggers water reabsorption from the late distal tubule and collecting system. e. False: Facultative water reabsorption occurs in the distal tubule and collecting system.

8. Fill in the blanks for the following statements: a. When the GFR decreases, the macula densa releases chemicals to __________ the afferent arteriole. b. The sympathetic nervous system __________ the blood vessels supplying the kidney to __________ the glomerular filtration rate. c. The enzyme __________ is released by JG cells in response to a decrease in the GFR. d. The enzyme __________ converts angiotensin-I to angiotensin-II. e. Generally, angiotensin-II __________ systemic blood pressure while __________ the GFR.

a. dilate b. constricts; reduce c. renin d. angiotensin-converting enzyme e. increases; maintaining

17. Fill in the blanks for each of the following statements: a. The process by which urine is eliminated is called __________, and it is mediated by reflexes involving the __________ nervous system. b. The mucosa of the organs of the urinary tract is lined with __________ epithelium. c. The three layers of smooth muscle in the urinary bladder are known as the __________ muscle. d. The female urethra provides a passageway for __________, whereas the male urethra provides a passageway for __________ and __________.

a. micturition; parasympathetic b. transitional c. detrusor d. urine; urine and semen

16. The GFR may be estimated by measuring the rate at which certain substances are removed from the blood, which is known as: a. renal clearance. b. plasma creatinine. c. glomerular hydrostatic pressure. d. inulin estimation.

a. renal clearance

13. Which of the following conditions does not contribute to the creation and/or maintenance of the medullary osmotic gradient? a. The countercurrent exchanger of the vasa recta b. The countercurrent multiplier of the nephron loops of cortical nephrons c. The countercurrent multiplier of the nephron loops of juxtamedullary nephrons d. The permeability of the medullary collecting system to urea and other ions

b. The countercurrent multiplier of the nephron loops of cortical nephrons

10. The route by which substances are reabsorbed by crossing through the cells of the renal tubule and collecting system is known as the: a. paracellular route. b. transcellular route. c. primary active transport route. d. secondary active transport route.

b. transcellular route.

12. Dilute urine is produced when decreased levels of __________ are secreted: a. aldosterone b. atrial natriuretic peptide c. ADH d. none of the above

c. ADH

9. Which of the following is false about the GFR? a. The GFR averages about 120 ml/min. b. The GFR increases when the afferent arteriole dilates. c. The GFR decreases when the efferent arteriole constricts. d. The GFR decreases when the afferent arteriole constricts.

c. The GFR decreases when the efferent arteriole constricts.

7. Fill in the blanks: Glomerular hydrostatic pressure __________ filtration; colloid osmotic pressure and capsular hydrostatic pressure __________ filtration. a. favors; favor b. opposes; oppose c. favors; oppose d. opposes; favor

c. favors; oppose

14. Fill in the blanks: The kidneys produce __________ urine when the osmolarity of the body's fluids increases. They produce __________ urine when the osmolarity of the body's fluids decreases.

concentrated; dilute

The kidneys produce *blank* urine when the osmolarity of the body's fluid increases. They produce *blank* urine when the osmolarity of the body's fluid decreases

concentrated; dilute

Describe the structure of the filtration membrane

consist of a series of 3 progressively finer fibers, including the glomerular epithelial cells, the basal lamina, and the filtration slits of the podocytes

4. Cortical and juxtamedullary nephrons differ in the: a. lengths of their nephron loops. b. structure of the capillaries surrounding them. c. structure of their renal corpuscles. d. Both a and b are correct. e. Both b and c are correct

d. Both a and b are correct.

2. Which of the following is not a physiological process carried out by the kidneys? a. Blood pressure regulation b. Tubular reabsorption c. Tubular secretion d. Glomerular filtration e. All of the above are physiological processes carried out by the kidneys.

e. All of the above are physiological processes carried out by the kidneys.

Glomerular hydrostatic pressure *blank* filtration; colloid osmotic pressure and capsular hydrostatic pressure *blank* filtration

favor; opposes

24.9.5. How is the micturition consciously controlled?

given time and training makes the micturition a voluntary process -> when time and place is not appropriate -> inhibitory signals from pons -> constrict external urethral sphincter (voluntary) and inhibit motor signals to detrusor muscle. When time and place is appropriate -> inhibitory signal is not sent out anymore -> external sphincter is not stimulated anymore, no inhibitory signal sent to detrusor.

24.2.4. Trace the sequence of blood flow through the kidneys from the renal artery to the renal vein. Renal corpuscle

renal artery -> segmental artery -> interlobar artery -> arcuate artery -> interlobular or cortical radiate artery -> afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries

The enzyme *blank* is released by JG cells int the response to a decrease in the GFR

renin

Cortical and juxtamedullary nephrons differ in

the length in their nephron loop and structure of capillary surrounding them

The mucosa of the organs of the urinary tract is lined with *blank* epithelium

transitional