Anatomy and Phys II Exam 4 Urinary System
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Free Anatomy and Phys II Exam 4 Urinary System Questions
Cells and transport proteins are physically prevented from passing through the filtration membrane. This has the following effect on filtration:
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Increased osmotic pressure in the filtrate that draws plasma through the membrane
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Decreased osmotic pressure in the filtrate that increases the amount of filtration
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Neutral change in osmotic pressure with no effect on filtration
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Increasing osmotic pressure in the glomerular capillaries that reduces the amount of filtration
Explanation
Explanation:
Correct Answer: (D) Increasing osmotic pressure in the glomerular capillaries that reduces the amount of filtration
When cells and large proteins are prevented from crossing the filtration membrane, they remain behind in the glomerular capillaries. This increases the colloid osmotic pressure (oncotic pressure) within the capillaries as filtration progresses. This rising osmotic pressure opposes further filtration by drawing fluid back into the capillaries, thereby reducing the net amount of filtration that occurs.
Why Other Options are Incorrect:
- A. Increased osmotic pressure in the filtrate that draws plasma through — The filtrate has low osmotic pressure because large proteins are excluded from it; it is the capillary side that has high osmotic pressure, not the filtrate side.
- B. Decreased osmotic pressure in the filtrate that increases filtration — While the filtrate does have low osmotic pressure due to absence of proteins, this does not increase filtration; rather the high capillary osmotic pressure opposes and reduces filtration.
- C. Neutral change in osmotic pressure with no effect on filtration — This is incorrect; the retention of proteins in the capillaries significantly increases capillary osmotic pressure, which has a measurable opposing effect on filtration.
The mechanism that establishes the medullary osmotic gradient depends most on the permeability properties of the _______.
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Loop of Henle
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Collecting duct
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Glomerular filtration membrane
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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.
Which of the following does NOT describe the juxtaglomerular complex?
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Its granular cells produce renin
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It regulates the rate of filtrate formation
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Its macula densa cells produce aldosterone
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It helps control systemic blood pressure
Explanation
Explanation:
Correct Answer: (C) Its macula densa cells produce aldosterone
The macula densa cells of the juxtaglomerular complex do NOT produce aldosterone. The macula densa cells are chemoreceptors that monitor the NaCl concentration of the filtrate and send signals to the granular cells to regulate renin release. Aldosterone is produced by the adrenal cortex, not by the macula densa cells.
Why Other Options are Incorrect:
- A. Its granular cells produce renin — This is TRUE; the granular (juxtaglomerular) cells are the primary source of renin secretion.
- B. It regulates the rate of filtrate formation — This is TRUE; by controlling afferent arteriole diameter through renin release, the juxtaglomerular complex regulates glomerular filtration rate.
- D. It helps control systemic blood pressure — This is TRUE; through the renin-angiotensin-aldosterone system (RAAS), the juxtaglomerular complex plays a key role in regulating blood pressure.
Which of the following hormones acting on the distal convoluted tubule is most responsible for retaining sodium ions in the blood?
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Parathyroid hormone
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Aldosterone
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Atrial natriuretic peptide
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Antidiuretic hormone
Explanation
Explanation:
Correct Answer: (B) Aldosterone
Aldosterone is the primary hormone responsible for sodium retention in the blood. It acts on the principal cells of the distal convoluted tubule and collecting duct to increase the number of sodium channels and Na⁺/K⁺-ATPase pumps in the cell membranes, promoting sodium reabsorption from the filtrate back into the bloodstream. Water follows the reabsorbed sodium by osmosis, increasing blood volume and pressure.
Why Other Options are Incorrect:
- A. Parathyroid hormone — PTH acts on the DCT to increase calcium reabsorption and decrease phosphate reabsorption; it is not primarily responsible for sodium retention.
- C. Atrial natriuretic peptide — ANP actually promotes sodium excretion (natriuresis) by inhibiting sodium reabsorption in the collecting duct, having the opposite effect of aldosterone.
- D. Antidiuretic hormone — ADH primarily increases water reabsorption by inserting aquaporins in the collecting duct; while it indirectly affects sodium concentration, it is not the primary hormone responsible for sodium retention.
The mechanism of water reabsorption by the renal tubules is _______.
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Active transport
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Cotransport with sodium ions
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Filtration
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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.
Which of the following is the best explanation for why the cells of the proximal convoluted tubule (PCT) contain so many mitochondria?
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Contraction of the PCT moves filtrate through the tubule
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Cells of the PCT go through a great deal of mitosis
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This provides the energy needed to fight kidney infection
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A great deal of active transport takes place in the PCT
Explanation
Explanation:
Correct Answer: (D) A great deal of active transport takes place in the PCT
The PCT is the site of the most extensive reabsorption in the nephron, reabsorbing approximately 65% of filtered water, sodium, glucose, amino acids, and other solutes. Much of this reabsorption involves active transport, which requires ATP as an energy source. The large number of mitochondria in PCT cells reflects the high energy demand needed to power these numerous active transport processes.
Why Other Options are Incorrect:
- A. Contraction of the PCT moves filtrate through the tubule — The PCT does not contract; it is not a muscular structure. Filtrate movement is driven by hydrostatic pressure gradients, not tubular contraction.
- B. Cells of the PCT go through a great deal of mitosis — While PCT cells do have some regenerative capacity, frequent mitosis is not the reason for the high mitochondrial density.
- C. This provides the energy needed to fight kidney infection — Mitochondria in PCT cells are not specifically for immune defense; their presence reflects the metabolic demands of active reabsorption, not infection fighting.
The function of angiotensin II is to _______.
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Constrict arterioles and increase blood pressure
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Decrease the production of aldosterone
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Decrease water absorption
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Decrease arterial blood pressure
Explanation
Explanation:
Correct Answer: (A) Constrict arterioles and increase blood pressure
Angiotensin II is a potent vasoconstrictor that acts on arterioles throughout the body, causing them to constrict and thereby increasing systemic blood pressure. It also stimulates the adrenal cortex to release aldosterone, promotes ADH release, and increases sodium and water reabsorption — all of which work together to raise and maintain blood pressure.
Why Other Options are Incorrect:
- B. Decrease the production of aldosterone — Angiotensin II actually stimulates aldosterone production, not decreases it.
- C. Decrease water absorption — Angiotensin II promotes water retention by stimulating ADH release and aldosterone production, thereby increasing water absorption.
- D. Decrease arterial blood pressure — Angiotensin II raises arterial blood pressure through vasoconstriction; it does not decrease it.
The factor that increases filtrate formation at the glomerulus is the _______.
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Capsular hydrostatic pressure
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Colloid osmotic pressure of the blood
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Glomerular hydrostatic pressure
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Myogenic mechanism
Explanation
Explanation:
Correct Answer: (C) Glomerular hydrostatic pressure
Glomerular hydrostatic pressure is the primary driving force for filtrate formation at the glomerulus. It is the blood pressure within the glomerular capillaries that pushes fluid and small solutes out of the blood and into Bowman's capsule. The glomerular hydrostatic pressure is significantly higher than in other capillary beds due to the unique arteriole-to-arteriole arrangement of the glomerulus.
Why Other Options are Incorrect:
- A. Capsular hydrostatic pressure — Capsular hydrostatic pressure opposes filtration by pushing back against the flow of filtrate into Bowman's capsule; it decreases, not increases, filtrate formation.
- B. Colloid osmotic pressure of the blood — Colloid osmotic pressure (oncotic pressure) draws fluid back into the capillaries and opposes filtration; it decreases, not increases, filtrate formation.
- D. Myogenic mechanism — The myogenic mechanism is an autoregulatory response that maintains relatively constant GFR by adjusting afferent arteriole resistance; it regulates rather than directly increases filtrate formation.
The glomerular capsular space contains _______.
-
Filtrate
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Plasma
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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.
What is the most direct function of the juxtaglomerular apparatus?
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Help regulate urea absorption by the kidneys
-
Help regulate blood pressure and the rate of excretion by the kidneys
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Help regulate blood pressure and the rate of blood filtration by the kidneys
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Help regulate water and electrolyte excretion by the kidneys
Explanation
Explanation:
Correct Answer: (C) Help regulate blood pressure and the rate of blood filtration by the kidneys
The juxtaglomerular apparatus most directly regulates blood pressure and the glomerular filtration rate (GFR). It does this through the release of renin in response to decreased blood pressure or decreased NaCl delivery, initiating the RAAS cascade. It also monitors filtrate composition via the macula densa to adjust afferent arteriole resistance and thereby control the rate of blood filtration.
Why Other Options are Incorrect:
- A. Help regulate urea absorption — Urea handling is primarily a passive process in the tubules and is not a direct function of the juxtaglomerular apparatus.
- B. Help regulate blood pressure and the rate of excretion — While blood pressure regulation is correct, the juxtaglomerular apparatus more specifically regulates the rate of filtration, not excretion directly.
- D. Help regulate water and electrolyte excretion — Water and electrolyte balance is more directly regulated by ADH and aldosterone acting on the collecting duct and distal tubule, not by the juxtaglomerular apparatus directly.
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