Anatomy and Phys II Exam 4 Urinary System
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Free Anatomy and Phys II Exam 4 Urinary System Questions
The glomerulus differs from other capillaries in the body in that it _______.
- Has a basement membrane
- Is impermeable to most substances
- Has a blood pressure much lower than other organ systems
- Is drained by an efferent arteriole
Explanation
Explanation:
Correct Answer: (D) Is drained by an efferent arteriole
The glomerulus is unique among capillary beds in the body because it is both fed by an afferent arteriole AND drained by an efferent arteriole, rather than draining into a venule as all other capillary beds do. This arrangement of arteriole-to-arteriole creates and maintains the high hydrostatic pressure within the glomerulus that drives filtration.
Why Other Options are Incorrect:
- A. Has a basement membrane — All capillaries in the body have a basement membrane; this is not unique to the glomerulus.
- B. Is impermeable to most substances — The glomerulus is actually highly permeable compared to other capillaries, featuring fenestrations that allow large volumes of fluid and small solutes to filter through.
- C. Has a blood pressure much lower than other organ systems — The glomerulus actually maintains a higher hydrostatic pressure than most capillary beds, which is essential for driving glomerular filtration.
Which of the following acts as the trigger for the initiation of micturition (voiding)?
- Motor neurons
- The sympathetic efferents
- The pressure of the fluid in the bladder
- The stretching of the bladder wall
Explanation
Explanation:
Correct Answer: (D) The stretching of the bladder wall
Micturition (voiding) is initiated when the bladder wall stretches as it fills with urine. Stretch receptors (mechanoreceptors) in the detrusor muscle of the bladder wall detect this stretching and send afferent signals to the micturition center in the sacral spinal cord, triggering the micturition reflex. This leads to parasympathetic stimulation causing detrusor muscle contraction and internal urethral sphincter relaxation.
Why Other Options are Incorrect:
- A. Motor neurons — Motor neurons are involved in the efferent (output) response of micturition, carrying signals to the bladder to contract, but they are not the initial trigger for voiding.
- B. The sympathetic efferents — Sympathetic stimulation actually promotes urine storage by relaxing the detrusor muscle and contracting the internal urethral sphincter; it does not trigger micturition.
- C. The pressure of the fluid in the bladder — While increased fluid volume contributes to bladder pressure, it is specifically the mechanical stretching of the bladder wall detected by stretch receptors that triggers the micturition reflex, not fluid pressure alone.
The mechanism of water reabsorption by the renal tubules is _______.
- Active transport
- Cotransport with sodium ions
- Filtration
- Osmosis
Explanation
Explanation:
Correct Answer: (D) Osmosis
Water reabsorption throughout the renal tubules occurs entirely by osmosis — the passive movement of water from an area of lower solute concentration (tubular lumen) to an area of higher solute concentration (interstitium and peritubular capillaries). Water follows the osmotic gradient created by the active reabsorption of solutes, particularly sodium, and requires no energy itself.
Why Other Options are Incorrect:
- A. Active transport — Active transport requires energy (ATP) and is used for solute reabsorption such as sodium and glucose, not for water reabsorption.
- B. Cotransport with sodium ions — Sodium cotransport is the mechanism for reabsorbing glucose, amino acids, and other solutes, not water directly.
- C. Filtration — Filtration occurs at the glomerulus to produce the filtrate; it is not the mechanism by which water is reabsorbed along the tubules.
Alcohol acts as a diuretic because it _______.
- Inhibits the release of ADH
- Increases secretion of ADH
- Increases the rate of glomerular filtration
- Is not reabsorbed by the tubule cells
Explanation
Explanation:
Correct Answer: (A) Inhibits the release of ADH
Alcohol inhibits the release of antidiuretic hormone (ADH) from the posterior pituitary gland. Without adequate ADH, the collecting duct remains impermeable to water, preventing water reabsorption. As a result, large volumes of dilute urine are produced, leading to the diuretic effect and the dehydration commonly associated with alcohol consumption.
Why Other Options are Incorrect:
- B. Increases secretion of ADH — This is the opposite of what alcohol does; increased ADH would promote water retention and concentrated urine, not diuresis.
- C. Increases the rate of glomerular filtration — Alcohol does not significantly increase GFR; its diuretic effect is specifically due to ADH inhibition, not increased filtration.
- D. Is not reabsorbed by the tubule cells — Alcohol is not a substance that is handled by tubular reabsorption or secretion in a way that causes diuresis; the mechanism is entirely through ADH suppression.
The presence of protein in the urine indicates which of the following?
- Damage to the filtration membrane
- High levels of transcription and translation by the body's tissues
- Damage to the renal tubules
- Too much protein in the diet
Explanation
Explanation:
Correct Answer: (A) Damage to the filtration membrane
Protein molecules, particularly albumin, are normally too large to pass through the intact glomerular filtration membrane. The presence of significant protein in the urine (proteinuria) indicates that the filtration membrane has been damaged, allowing proteins to leak through into the filtrate. This is a hallmark sign of glomerular diseases such as glomerulonephritis and nephrotic syndrome.
Why Other Options are Incorrect:
- B. High levels of transcription and translation by the body's tissues — Protein synthesis activity in body tissues does not directly cause protein to appear in urine; it is the integrity of the filtration membrane that determines protein loss.
- C. Damage to the renal tubules — Tubular damage would affect reabsorption and secretion of small molecules, not typically result in significant proteinuria, as protein filtration is primarily controlled at the glomerular level.
- D. Too much protein in the diet — Dietary protein intake does not directly cause proteinuria; the kidneys efficiently handle normal variations in dietary protein without allowing protein into the urine.
If the diameter of the efferent arterioles leading away from the glomerulus increases (vasodilation), which of the following is NOT likely to occur?
- Systemic blood pressure will decrease
- Glomerular filtration rate will decrease
- Net filtration pressure will decrease
- Urine output will decrease
Explanation
Explanation:
Correct Answer: (A) Systemic blood pressure will decrease
When the efferent arteriole vasodilates, blood drains away from the glomerulus more easily, which reduces glomerular hydrostatic pressure. This leads to decreased net filtration pressure, decreased GFR, and decreased urine output. However, systemic blood pressure decreasing is NOT a direct or expected consequence of efferent arteriole vasodilation alone — efferent dilation primarily affects glomerular dynamics locally, not systemic blood pressure directly.
Why Other Options are Incorrect (i.e., these WOULD likely occur):
- B. Glomerular filtration rate will decrease — TRUE; with easier outflow through the dilated efferent arteriole, glomerular hydrostatic pressure drops, reducing GFR.
- C. Net filtration pressure will decrease — TRUE; reduced glomerular hydrostatic pressure means less driving force for filtration, lowering net filtration pressure.
- D. Urine output will decrease — TRUE; a lower GFR means less filtrate is produced, resulting in decreased urine output.
If the diameter of the afferent arterioles leading to the glomerulus increases (vasodilation), which of the following is NOT likely to occur?
- Net filtration pressure will increase
- Glomerular filtration rate will increase
- Systemic blood pressure will go up
- Urine output will increase
Explanation
Explanation:
Correct Answer: (C) Systemic blood pressure will go up
When afferent arterioles vasodilate, more blood flows into the glomerulus, increasing glomerular hydrostatic pressure, net filtration pressure, GFR, and ultimately urine output. However, afferent arteriole vasodilation actually decreases systemic blood pressure because blood is being redirected into the kidney's capillary beds, reducing peripheral vascular resistance. Therefore, systemic blood pressure going up is NOT an expected outcome.
Why Other Options are Incorrect (i.e., these WOULD likely occur):
- A. Net filtration pressure will increase — TRUE; increased blood flow into the glomerulus raises hydrostatic pressure, increasing net filtration pressure.
- B. Glomerular filtration rate will increase — TRUE; greater blood flow and increased hydrostatic pressure directly increase GFR.
- D. Urine output will increase — TRUE; a higher GFR means more filtrate is produced, leading to increased urine output.
The mechanism that establishes the medullary osmotic gradient depends most on the permeability properties of the _______.
- Loop of Henle
- Collecting duct
- Glomerular filtration membrane
- Distal convoluted tubule
Explanation
Explanation:
Correct Answer: (A) Loop of Henle
The countercurrent multiplier system of the loop of Henle is responsible for establishing and maintaining the medullary osmotic gradient. The descending limb is permeable to water but not solutes, while the ascending limb actively transports NaCl out into the medullary interstitium but is impermeable to water. This difference in permeability properties between the two limbs creates the progressively increasing osmotic gradient from the cortex to the medulla that is essential for urine concentration.
Why Other Options are Incorrect:
- B. Collecting duct — The collecting duct responds to the existing medullary gradient by reabsorbing water under the influence of ADH, but it does not establish the gradient itself.
- C. Glomerular filtration membrane — The glomerular filtration membrane is involved in filtering plasma, not in establishing the medullary osmotic gradient.
- D. Distal convoluted tubule — The distal convoluted tubule plays a role in fine-tuning electrolyte balance but does not establish the medullary osmotic gradient.
The glomerular capsular space contains _______.
- Filtrate
- Plasma
- Urine
- Blood
Explanation
Explanation:
Correct Answer: (A) Filtrate
The glomerular capsular space (the space within Bowman's capsule between the visceral and parietal layers) contains filtrate — the fluid that has been filtered from the blood through the glomerular filtration membrane. This filtrate is essentially plasma minus the large proteins and blood cells, and it will be further processed as it moves through the renal tubules to eventually become urine.
Why Other Options are Incorrect:
- B. Plasma — Plasma remains within the glomerular capillaries; only the filtered portion (minus large proteins) crosses into the capsular space as filtrate.
- C. Urine — Urine is the final product after tubular processing of the filtrate; it is not present in the glomerular capsular space, which is the very beginning of the nephron.
- D. Blood — Blood is contained within the glomerular capillaries and does not enter the capsular space; only the filtered fluid crosses the filtration membrane.
An increase in the permeability of the cells of the collecting duct to water is due to a(n) _______.
- Increase in the production of aldosterone
- Decrease in the production of ADH
- Decrease in the concentration of the blood plasma
- Increase in the production of ADH
Explanation
Explanation:
Correct Answer: (D) Increase in the production of ADH
Antidiuretic hormone (ADH), also known as vasopressin, is responsible for increasing the permeability of the collecting duct cells to water. When ADH is released from the posterior pituitary gland, it binds to receptors on collecting duct cells, triggering the insertion of aquaporin channels into the cell membranes. This allows water to be reabsorbed from the filtrate back into the bloodstream, concentrating the urine.
Why Other Options are Incorrect:
- A. Increase in the production of aldosterone — Aldosterone acts on the collecting duct to increase sodium reabsorption and potassium excretion, not to increase water permeability directly.
- B. Decrease in the production of ADH — A decrease in ADH would reduce water permeability of the collecting duct, resulting in more dilute urine and increased urine output.
- C. Decrease in the concentration of the blood plasma — A decrease in blood plasma concentration would actually suppress ADH release, reducing water reabsorption rather than increasing it.
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