Chapter Review - Urinary System

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The Lowest blood concentration of nitrogenous waste occurs in the

A)Hepatic vein
B)Inferior vena cava
C)Renal artery
D)Renal vein

D)Renal vein


The Glomerular capillaries differ from other capillary networks in the body because they

A)Have a larger area of anastomosis
B)are derived from & drain into the arterioles
C)are not made of epithelium
D)are sites of filtrate formation

B)are derived from & drain into the arterioles


Damage to the renal medulla would interfere first with the functioning of the

A)Glomerular capsule
B)Distal convoluted tubules
C)Collecting ducts
D)Proximal convoluted tubules

C)Collecting ducts


Which reabsorbed by the proximal convoluted tubule cells

C)Amino acids
D)All of the above

D)All of the above


Glucose is not normally found in urine because it

A)Does not pass through the wall of the glomerulus
B)Is kept in the blood by colloid osmotic pressure
C)is reabsorbed by the tubule cells
D)is removed by the body cells before the blood reaches the kidney

C)is reabsorbed by the tubule cells


Filtration at the glomerulus is inversely related to

A)Water reabsorption
B)Capsular hydrostatic pressure
C)Arterial blood pressure
D)Acidity of the urine

B)Capsular hydrostatic pressure


Tubular reabsorption

A)Of glucose and many substances is a Tm-limited active transport process
B)Of chloride is always linked to the passive transport of Na+
C)Is the movement of substances from blood into nephron
D)Of sodium occurs only in the proximal tubule

A)Of glucose and many substances is a Tm-limited active transport process


If a freshly voided urine sample contains excessive amounts of urochrome, it has

A)An ammonia-like odor
B)A pH below normal
C)A dark yellow color
D)A pH above normal

C)A dark yellow color


Conditions such as diabetes mellitus and starvation are closely linked




Which of the following is true about ADH?
A)It promotes obligatory water reabsorption
B)It is secreted in response to an increase in extra cellular fluid osmolarity
C)It cause insertion of aquaporins in the PCT
D)It promotes Ns+ reabsorption

B)It is secreted in response to an increase in extra cellular fluid osmolarity


What is the importance of the perirenal fat capsule that surrounds the kidney?

The perineal fat capsule helps to hold the kidney in place against the posterior trunk wall and cushions it against blows


Trace the pathway a creatinine molecule takes from the glomerulus to the urethra. Name every microscopic of gross structure it passes through on its journey.

A creatine molecule travels the following route from a glomerulus to the urethra. It first passes through the glomerular filtration membrane, which is a porous membrane made up of a fenestrated capillary endothelium, a thin basement membrane, and the visceral membrane of the glomerular capsule formed by the podocytes. The creatine molecule then passes through the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule, and into the collecting duct in which it travels into the medulla through the renal pyramids. From the medulla the molecule enters the renal pelvis, and leaves the kidney via the ureter. Then it travels to the urinary bladder and then to the urethra.


Explain the important differences between blood plasma and glomerular filtrate, and relate the differences to the structure of the filtration membrane

Renal filtrate is a solute-rich fluid without blood cells or plasma proteins because the filtration membrane is permeable to water and all solutes smaller than plasma proteins. The capillary endothelium restricts passage of formed elements, whereas the anion-rich basement membrane holds back most protein and some smaller anionic molecules.


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.


Describe the mechanisms of extrinsic regulation of GFR, and their psychological 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

In active tubular reabsorption, substances are usually moving against electrical and/or chemical gradients. The substances usually move from the filtrate into the tubule cells by secondary active transport coupled to Na+ transport and move across the basolateral membrane of the tubule cell into the interstitial space by diffusion. Most such processes involve cotransport with sodium.

Passive tubular reabsorption encompasses diffusion, facilitated diffusion, and osmosis. Substances move along their electrochemical gradient without the use of metabolic energy.


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

Tubular secretion is important for the following reasons: (a) disposing of substances not already in the filtrate; (b) eliminating undesirable substances that have been reabsorbed by passive processes; (c) ridding the body of excessive potassium ions; and (d) controlling blood pH. Tubular secretion moves materials from the blood of the peritubular capillaries through the tubule cells or from the tubule cells into the filtrate.


How does aldosterone modify the chemical composition of urine?

Aldosterone modifies the chemical composition of urine by enhancing sodium ion reabsorption so that very little leaves the body in urine.


Explain why the filtrate becomes hypotonic as it flows through the ascending limb of the loop of henle. Also explain why the filtrate at the bend of the nephron loop (and 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

(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.


How does urinary bladder anatomy supportits storage function

The bladder is very distensible. An empty bladder is collapsed and has rugae. Expansion of the bladder to accommodate increased volume is due to the ability of the transitional epithelial cells lining the interior of the bladder to slide across one another, thinning the mucosa, and the ability of the detrusor muscle to stretch.


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 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.


Critical Thinking

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).

a. How will diuretics reduce this excess fluid?

b. Name and describe the mechanism of action of two types of diuretics.

c. 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 are
oOsmotic 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.


Critical Thinking

While repairing a frayed utility wire, Herbert, an experienced lineman, slips and falls to the ground. Medical examination reveals a fx of the lower spine and transection of the lumber region of the spinal cord. How will Herbert’s micturation be controlled from this point on? Explain your rationale. Will he ever feel the need to void again? Explain your rationale. Will there be dribbling of urine between voiding? Explain your rationale.

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.


Critical Thinking

What is cystitis? Why do women suffer from cystitis more frequently than men?

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


Critical Thinking

Hattie, age 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 occurs at interval of 3 to 4 minutes. Dx her problem and site factors that might favor its occurrence. Explain why Hattie’s’ pain comes in “waves.”

Hattie has a renal calculus, or kidney stone, in her ureter. Predisposing conditions are frequent bacterial infections of the urinary tract, urinary retention, high concentrations of calcium in the blood, and alkaline urine. Her pain comes in waves because waves of peristalsis pass along the ureter at intervals. The pain results when the ureter walls close in on the sharp kidney stone during this peristalsis.


Critical Thinking

Why does use of spermicide increase a women’s risk for urinary tract infections

The use of spermicides in females kills many helpful bacteria, allowing infectious fecal bacteria to colonize the vagina. Intercourse will drive bacteria from the vagina into the urethra, increasing the incidence of urinary tract infection in these females.


Critical Thinking

Why are renal failure patients undergoing dialysis at risk for anemia and osteoporosis? What edications of suppliments 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

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