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Urinary System Review Questions Chapter 25

Terms in this set (50)

The lowest blood concentration of nitrogenous waste occurs in the
Renal vein
The glomerular capillaries differ from other capillary networks in the body because they
are derived from and drain into arterioles
Damage to the renal medulla would interfere first with the functioning of the
Collecting ducts
Which is reabsorbed by the proximal convoluted tubule cells?
Na, K, and amino acids
Glucose is not normally found in the urine because it
is reabsorbed by the tubule cells
Filtration at the glomerulus is inversely related to
capsular hydrostatic pressure
tubular reabsorption
of glucose and many other substances is a Tm-limited active transport process
If a freshly voided urine sample contains excessive amounts of urochrome
a dark yellow color
Which of the following is/are true about ADH?
it is secreted in response to an increase in extracellular fluid osmolality
What is the importance of the perirenal fat capsule that surrounds the kidney?
Perinephric fat, also known as perirenal fat or the adipose capsule of the kidney, is a layer of fatty material that surrounds the kidneys. It plays an important role because it helps to cushion and protect the kidneys.
Define micturition and describe the micturition reflex.
Micturition is the act of emptying the bladder. The micturition reflex is activated when distension of the bladder wall activates stretch receptors. Afferent impulses are transmitted to the sacral region of the spinal cord and efferent impulses return to the bladder via the parasympathetic pelvic splanchnic nerves, causing the detrusor muscle to contract and the internal sphincter to relax.
Describe the mechanisms that contribute to renal autoregulation.
The mechanisms that contribute to renal autoregulation are the myogenic mechanism and the tubuloglomerular feedback mechanism. The myogenic mechanism reflects the tendency of vascular smooth muscle to contract when it is stretched. An increase in systemic blood pressure causes afferent arterioles to constrict, which impedes blood flow into the glomerulus and prevents glomerular blood pressure from rising to damaging levels. Conversely, a decline in systemic blood pressure causes dilation of afferent arterioles and an increase in glomerular hydrostatic pressure. Both responses help maintain a normal GFR.The tubuloglomerular mechanism reflects the activity of the macula densa cells in response to a slow filtration rate or low filtrate osmolarity. When so activated they release chemicals that cause vasodilation in the afferent arterioles.Renal autoregulation maintains a relatively constant kidney perfusion over an arterial pressure range from about 80 to 180 mm Hg, preventing large changes in water and solute excretion. (p. 972)
Describe the mechanisms of extrinsic regulation of GFR, and their physiological role.
Sympathetic nervous system controls protect the body during extreme stress by redirecting blood to more vital organs. Strong sympathetic stimulation causes release of norepinephrine to alpha-adrenergic receptors, causing strong vasoconstriction of kidney arterioles. This results in a drop in glomerular filtration, and indirectly stimulates another extrinsic mechanism, the renin-angiotensin mechanism. The renin-angiotensin mechanism involves the release of renin from the granular juxtaglomerular cells, which enzymatically converts the plasma globulin angiotensinogen to angiotensin I. Angiotensin I is further converted to angiotensin II by angiotensin converting enzyme (ACE) produced by capillary endothelium. Angiotensin II causes vasoconstriction of systemic arterioles, increased sodium reabsorption by promoting the release of aldosterone, decreases peritubular hydrostatic pressure, which encourages increased fluid and solute reabsorption, and acts on the glomerular mesangial cells, causing a decrease in glomerular filtration rate. In addition, angiotensin II results in stimulation of the hypothalamus, which activates the thirst mechanism and promotes the release of antidiuretic hormone, which causes increased water reabsorption in the distal nephron. Other factors that may trigger the renin-angiotensin mechanism are a drop in mean systemic blood pressure below 80 mm Hg, and activated macula densa cells responding to low plasma sodium.
Describe what is involved in active and passive tubular reabsorption.
Passive tubular reabsorption is the passive reabsorption of negatively charged ions that travel along an electrical gradient created by the active reabsorption of Na+.
Explain how the peritubular capillaries are adapted for receiving reabsorbed substances.
The peritubular capillaries are low-pressure, porous capillaries that readily absorb solutes and water from the tubule cells. They arise from the efferent arteriole draining the glomerulus
Explain the process and purpose of tubular secretion.
Process whereby selected molecules are actively transported from the blood into the filtrate secretionThe only difference between secretory and reabsorptive tubular mechanisms lies in the direction of transport; secretory mechanisms involve the addition of substances to the filtrate from the plasma in the peritubular capillaries. The small amount of secretion that does occur, except for the secretion of potassium and uric acid, takes place in the proximal tubule. Hydrogen ions are also secreted and ammonia is generated. As in the case of reabsorption, secretion occurs both passively and actively against an electrochemical gradient.
How does urinary bladder anatomy support its storage function?
It has elastic walls which allow it to expand to up to 15 times its empty volume. It has a sphincter muscle to hold the urine in. The walls include a layer of smooth muscle which can assist in emptying it and the walls also contain receptors which transmit information about how much the walls are stretched.
Describe the changes that occur in kidney and bladder anatomy and physiology in old age.
In old age the kidneys become smaller, the nephrons decrease in size and number, and the tubules become less efficient. By age 70, the rate of filtrate formation is only about one half that of middle-aged adults. This slowing is believed to result from impaired renal circulation caused by arteriosclerosis. The bladder is shrunken, with less than half the capacity of a young adult. Problems of urine retention and incontinence occur.
Trace the pathway a creatinine molecule takes from a glomerulus to the urethra. Name every microscopic or gross structure it passes through on its journey.
GLOMERULUS (connecting point with blood supply) ----> filtrate ---->into space of Bowman's capsule ---->proximal convoluted tubule (smaller, brush border of microvilli, cuboidal epithelium) ---->loop of Henle (descending and ascending) ---->distal convoluted tubule (macula densa) (no microvilli, larger lumen) ---->collecting duct ---->minor calyx ---->major calyx (pl. calyces) ---->renal pelvis (sinus outside) ---->ureter ---->bladder ---->urethra ---->urethral orifice
Explain the important differences between blood plasma and glomerular filtrate, and relate the differences to the structure of the filtration membrane.
The plasma that is filtered is known as "renal filtrate" and is similar to plasma, except that the circulating globular proteins are too big to be filtered
How does aldosterone modify the chemical composition of urine?
Aldosterone increases absorption of sodium and excretion of potassium in the collecting ducts and to some extent in the distal convoluted tubules of the nephron of the kidneys.Therefore urine will ultimately have fewer sodium and more potassium.
Explain why the filtrate becomes hypotonic as it flows through the ascending limb of the nephron loop. Also explain why the filtrate at the bend of the nephron loop (and the interstitial fluid of the deep portions of the medulla) is hypertonic.
As it flows through the ascending limb of the loop of Henle, the filtrate becomes hypotonic because it is impermeable to water, and because sodium and chloride are being actively pumped into the interstitial fluid, thereby decreasing solute concentration in the tubule. The interstitial fluid at the tip of the loop of Henle and the deep portions of the medulla are hypertonic because:(1) the loop of Henle serves as a countercurrent multiplier to establish the osmotic gradient, a process that works due to the characteristics of tubule permeability to water in different areas of the tubule and ion transport to the interstitial areas; and(2) the vasa recta acts as a countercurrent exchanger to maintain the osmotic gradient by serving as a passive exchange mechanism that removes water from the medullary areas but leaves salts behind. The filtrate at the tip of the loop of Henle is hypertonic due to the passive diffusion of water from the descending limb to the interstitial areas. (pp. 979-981)
Mrs. Bigda, a 60-year-old woman, was brought to the hospital by the police after falling to the pavement. She is found to have alcoholic hepatitis. She is put on a salt- and protein-restricted diet and diuretics are prescribed to manage her ascites (accumulated fluid in the peritoneal cavity). How will diuretics reduce this excess fluid? Name and describe the mechanisms of action of three types of diuretics. Why is her diet salt-restricted?
Diuretics will remove water from the blood and eliminate it in the urine. Consequently, water will move from the peritoneal cavity into the bloodstream reducing her ascites.•The mechanism of action of diuretics areoOsmotic diuretics are substances that are not reabsorbed or that exceed the ability of the tubule to reabsorb it, which increases osmolarity of the urine, and causes water to be drawn into the urine from the ISF.oLoop diuretics (Lasix) inhibit symporters in the loop of Henle by diminishing sodium chloride uptake. They reduce the normal hyperosmolality of the medullary interstitial fluid, reducing the effects of ADH, resulting in loss of NaCl and water.oThiazides act on the distal convoluted tubule to inhibit water reabsorption.•Her diet is salt-restricted because if salt content in the blood is high, it will cause her to retain water rather than allowing her to eliminate it.
While repairing a frayed utility wire, Kevin, an experienced lineman, slips and falls to the ground. Medical examination reveals a fracture of his lower spine and transection of the lumbar region of the spinal cord. How will Kevin's micturition be controlled from this point on? Will he ever again feel the need to void? Will there be dribbling of urine between voidings? Explain the reasoning behind all your responses.
A fracture at the lumbar region will stop the impulses to the brain, so there will be no voluntary control of micturition and he will never again feel the urge to void. There will be no dribbling of urine between voidings as long as the internal sphincter is undamaged. Micturition will be triggered in response to bladder stretch by a reflex arc at the sacral region of the spinal cord as it is in an infant.
Patty, aged 55, is awakened by excruciating pain that radiates from her right abdomen to the loin and groin regions on the same side. The pain is not continuous but recurs at intervals of 3 to 4 minutes. Diagnose her problem, and cite factors that might favor its occurrence.
Cystitis is bladder inflammation. Women are more frequent cystitis sufferers than men because the female urethra is very short and its external orifice is closer to the anal opening. Improper toilet habits can carry fecal bacteria into the urethra
Why are renal failure patients undergoing dialysis at risk for anemia and osteoporosis? What medications or supplements could you give them to prevent these problems?
Renal failure patients accumulate both phosphorus and water between dialysis appointments. Increased levels of phosphorus can lead to leaching of calcium from the bones. Increased water can lead to relatively decreased red blood cell counts. Calcium/magnesium supplements can offset calcium loss from bones, but water intake should be carefully monitored to prevent accumulation in the plasma
Zach is hit in the lower back by an errant baseball. What protects his kidneys from this mechanical trauma?
The lower part of his rib cage and the perirenal fat capsule protect his kidneys from blows.
From inside to outside, list the three layers of supportive tissue that surround each kidney. Where is the parietal peritoneum in relation to these layers?
The layers of supportive tissue around each kidney are the fibrous capsule, the perirenal fat capsule, and the renal fascia. The parietal peritoneum overlies the anterior renal fascia.
The lumen of the ureter is continuous with a space inside the kidney. This space has branching extensions. What are the names of this space and its extensions?
The renal pelvis, which has extensions called calyces, is continuous with the ureter.
Name the tubular components of a nephron in the order that filtrate passes through them.
Filtrate is formed in the glomerular capsule and then passes through the proximal convoluted tubule (PCT), the descending and ascending limbs of the nephron loop, and the distal convoluted tubule (DCT).
What are the structural differences between juxtamedullary and cortical nephrons, and between their capillary beds?
The structural differences are (1) juxtamedullary nephrons have long nephron loops (with long thin segments) and renal corpuscles that are near the cortex-medulla junction, whereas cortical nephrons have short nephron loops and renal corpuscles that lie more superficially in the cortex; (2) efferent arterioles of juxtamedullary nephrons supply vasa recta, while efferent arterioles of cortical nephrons supply peritubular capillaries.
What type of capillaries are the glomerular capillaries? What is their function?
The glomerular capillaries are fenestrated capillaries. (See Figure 19.3 on p. 711 to refresh your memory of capillary types.) Their function is to filter large amounts of plasma into the glomerular capsule.
For the juxtamedullary nephron and collecting duct illustrated below, name each of the structures labeled a-f.
The structures shown are (a) glomerular capsule, (b) efferent arteriole, (c) vasa recta, (d) proximal convoluted tubule (PCT), (e) collecting duct, and (f) nephron loop (ascending thin limb).
In the kidneys, tubular secretion of a substance usually results in its excretion as well. Explain the difference between excretion (defined in Chapter 1) and tubular secretion.
Excretion is a means of removing wastes from the body, whereas tubular secretion is the process of selectively moving substances from the blood into the filtrate. While secretion often leads to excretion, this is not always the case because something could be secreted in the proximal tubules and yet reabsorbed distally.
Extrinsic and intrinsic controls of GFR serve two different purposes. What are they?
Intrinsic controls serve to maintain a nearly constant GFR in spite of changes in systemic blood pressure. Extrinsic controls serve to maintain systemic blood pressure.
Which of the pressures that determine NFP is regulated by both intrinsic and extrinsic controls of GFR?
Hydrostatic pressure in the glomerular capillaries (HPgc) is regulated by intrinsic and extrinsic controls of GFR.
Calculate net filtration pressure given the following values: glomerular hydrostatic pressure = 50 mm Hg, blood colloid osmotic pressure = 25 mm Hg, capsular hydrostatic pressure = 20 Hg.
Net filtration pressure is 5 mm Hg [50 mm Hg − (25 mm Hg + 20 mm Hg)].
In which part of the nephron does most reabsorption occur?
The majority of reabsorption occurs in the proximal convoluted tubule.
How does the movement of Na+ drive the reabsorption of water and solutes?
The reabsorption of Na+ by primary active transport drives reabsorption of amino acids and glucose by secondary active transport. It also drives passive reabsorption of chloride, and reabsorption of water by osmosis. The reabsorption of water leaves behind other solutes, which become more concentrated and can therefore be reabsorbed by diffusion.
Primary and secondary active transport processes are shown in Figure 25.16 (and were introduced in Chapter 3). How do they differ?
In primary active transport, the energy for the process is provided directly by ATP. In secondary active transport, the energy for the process is provided by the Na+ concentration gradient established by active pumping of Na+ occurring elsewhere in the cell. As Na+ moves down its own concentration gradient, it drives the movement of another substance (e.g., glucose) against that substance's concentration gradient.
List several substances that are secreted into the kidney tubules.
H+, K+, NH4 +, creatinine, urea, and uric acid are all substances that are secreted into the kidney tubules.
Describe the special characteristics of the descending and ascending limbs of the nephron loop that cause the formation of the medullary osmotic gradient.
The descending limb of the nephron loop is permeable to water and impermeable to NaCl. The ascending limb is impermeable to water and permeable to NaCl.
Under what conditions is ADH released from the posterior pituitary? What effect does ADH have on the collecting ducts?
ADH is released from the posterior pituitary in response to hyperosmotic extracellular fluid (as sensed by hypothalamic osmoreceptors). ADH causes insertion of aquaporins into the apical membranes of the principal cells of the collecting ducts.
What are the three major nitrogenous wastes excreted in the urine?
The three major nitrogenous wastes excreted in urine are urea, creatinine, and uric acid.
What would you expect the normal clearance value for amino acids to be? Explain.
The normal renal clearance value for amino acids is zero. You would expect this because amino acids are valuable as nutrients and as the building blocks for protein synthesis, so it would not be good to lose them in the urine.
A kidney stone blocking a ureter would interfere with urine flow to which organ? Why would the pain occur in waves?
A kidney stone blocking the ureter would interfere with urine flow to the bladder. The pain would occur in waves that coincide with the peristaltic contractions of the smooth muscle of the ureter.
What is the trigone of the bladder, and which landmarks define its borders?
The trigone is a smooth triangular region at the base of the bladder. Its borders are defined by the openings for the ureters and the urethra.
Name the three regions of the male urethra.
The prostatic urethra, the intermediate part of the urethra, and the spongy urethra are the three regions of the male urethra.
How does the detrusor respond to increased firing of the parasympathetic fibers that innervate it?
The detrusor contracts in response to increased firing of parasympathetic nerves.
Compare the structure and regulation of the sphincters that control micturition to those that control defecation (Chapter 23).
In both cases (micturition and defecation) the external sphincters are skeletal muscle under voluntary control, and the internal sphincters are smooth muscle controlled by the autonomic nervous system.
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