Quiz: Human Excretion and Homeostasis — 22 questions

1. Regarding excretion and waste products, which statements are correct?

A. Excretion removes metabolic waste from an organism.

B. The lungs excrete carbon dioxide and water vapour in exhaled air.

C. The kidneys excrete urea, excess mineral salts, and water in urine.

D. Secretion releases useful substances from cells or glands.

E. The main human excretory wastes include carbon dioxide, water, bile pigments, urea, and mineral salts.

Answer: (A), (B), (C), (D), (E)

Explanation

Excretion removes metabolic waste, whereas secretion releases useful substances such as enzymes or saliva. The lungs remove carbon dioxide and water vapour, kidneys remove urea with excess salts and water, and the listed substances constitute the main human excretory wastes.

2. Concerning the distinction between excretion and secretion, select the correct statements:

A. The kidneys excrete urea in urine after it is produced by the liver.

B. Secretion refers to releasing metabolic waste from the body.

C. Excretion includes releasing useful enzymes from glands.

D. The lungs remove carbon dioxide generated during cellular respiration.

E. The liver produces urea during deamination of excess amino acids.

Answer: (A), (D), (E)

Explanation

The kidneys excrete urea in urine, but the liver produces urea during amino-acid deamination. The lungs remove respiratory carbon dioxide and water vapour, while secretion concerns useful substances rather than metabolic waste.

3. Which statements accurately identify organs and their excretory products?

A. The liver excretes urea directly in urine after deamination.

B. The kidneys remove urea, excess mineral salts, and water in urine.

C. The skin releases mineral salts, traces of urea, and water as sweat.

D. The lungs remove carbon dioxide and water vapour through exhalation.

E. The colon excretes bile pigments and excess mineral salts in faeces.

Answer: (B), (C), (D), (E)

Explanation

The kidneys excrete urea, excess mineral salts, and water in urine. The lungs excrete carbon dioxide and water vapour, and the skin contributes mineral salts, traces of urea, and water through sweat.

4. The main human excretory waste products include:

A. Digestive enzymes released by glands as metabolic waste.

B. Carbon dioxide and water produced during cellular respiration.

C. Bile pigments eliminated through the colon in faeces.

D. Urea formed during deamination of excess amino acids.

E. Mineral salts eliminated by the kidneys, skin, and colon.

Answer: (B), (C), (D), (E)

Explanation

The main human excretory waste products include carbon dioxide, water, bile pigments, urea, and mineral salts. The lungs handle respiratory carbon dioxide and water vapour, while the skin and colon remove the products specified in the remaining statements.

5. Regarding urinary transport and renal blood vessels, which statements are correct?

A. The ureters carry urine from the kidneys to the bladder.

B. The renal artery branches from the aorta and brings unfiltered blood to the kidney.

C. The urethra carries urine from the bladder out of the body.

D. The renal vein carries deoxygenated, filtered blood away from the kidney.

E. The renal artery carries filtered blood away from the kidney.

Answer: (A), (B), (C), (D)

Explanation

The ureters carry urine to the bladder, while the urethra carries urine out of the body. The renal artery brings oxygenated, unfiltered blood containing waste to the kidney, and the renal vein carries filtered blood away.

6. Which statements describe major roles or protective features of the urinary system?

A. Urea is an example of nitrogenous waste excreted by the urinary system.

B. Osmoregulation is a major function of the urinary system.

C. Adipose tissue and the renal capsule help protect each kidney.

D. The urinary system regulates body-fluid salt concentration.

E. Regulation of body-fluid pH is a urinary-system function.

Answer: (A), (B), (C), (D), (E)

Explanation

The urinary system regulates water balance, nitrogenous waste, body-fluid pH, and salt concentration. Its components include two kidneys, two ureters, the bladder, and the urethra; adipose tissue and the renal capsule provide kidney protection.

7. Concerning kidney and nephron structure, which statements are correct?

A. The renal tubule includes the loop of Henle and collecting ducts.

B. The renal corpuscle consists of Bowman's capsule and the glomerulus.

C. A nephron is the microscopic functional unit of the kidney.

D. The renal tubule includes the proximal and distal convoluted tubules.

E. Each human kidney contains approximately one million nephrons.

Answer: (A), (B), (C), (D), (E)

Explanation

A nephron is the microscopic functional unit of the kidney, and each kidney contains about one million nephrons. The renal corpuscle consists of the glomerulus and Bowman's capsule, whereas the renal tubule contains the listed tubular regions and collecting ducts.

8. A microscopic examination of a nephron would support which statements?

A. The renal corpuscle is formed by the loop of Henle and collecting ducts.

B. The renal tubule is surrounded by peritubular capillaries.

C. The renal corpuscle contains Bowman's capsule and the glomerulus.

D. The renal corpuscle lies in the kidney cortex.

E. The loop of Henle extends into the kidney medulla.

Answer: (B), (C), (D), (E)

Explanation

The Malpighian body, or renal corpuscle, lies in the cortex and contains Bowman's capsule and the glomerulus. The loop of Henle extends into the medulla, while the renal tubule is surrounded by peritubular capillaries.

9. Which structural features support filtration and transport in the nephron?

A. Renal-tubule epithelial cells possess microvilli that increase surface area.

B. The renal tubule includes the loop of Henle and collecting ducts.

C. The renal tubule includes proximal and distal convoluted tubules.

D. Each nephron is composed solely of epithelial tubes without vessels.

E. Renal-tubule epithelial cells contain many mitochondria for active transport.

Answer: (A), (B), (C), (E)

Explanation

Renal-tubule epithelial cells have microvilli that increase surface area and numerous mitochondria that supply energy for active transport. A nephron contains tubular, vascular, and duct components, and the renal tubule comprises the specified segments.

10. Regarding glomerular ultrafiltration, which statement is accurate?

A. Blood pressure in the glomerulus prevents plasma from entering Bowman's capsule.

B. Ultrafiltration moves whole blood cells into Bowman's capsule under low pressure.

C. Blood enters through the afferent arteriole and exits through the narrower efferent arteriole.

D. Plasma enters Bowman's capsule because the efferent arteriole is wider than the afferent arteriole.

E. Blood enters through the efferent arteriole and exits through the afferent arteriole.

Answer: (C)

Explanation

The afferent arteriole brings blood into the glomerulus, while the narrower efferent arteriole allows blood to leave. This arrangement produces high pressure that drives plasma into Bowman's capsule.

11. Concerning the glomerular filtration barrier, which statement is correct?

A. Large proteins pass through podocyte slits more readily than dissolved solutes.

B. Glomerular capillaries have thick multilayered walls that exclude most dissolved substances.

C. Thin single-layer capillary walls allow large proteins to leave the bloodstream.

D. Podocyte slits prevent small dissolved substances from entering Bowman's capsule.

E. Small dissolved substances enter Bowman's capsule, while large proteins remain in blood.

Answer: (E)

Explanation

Thin capillary walls and podocyte filtration slits allow small dissolved substances to enter Bowman's capsule. Large proteins remain in the bloodstream because they do not pass through the filtration barrier.

12. The characteristics of glomerular filtration include:

A. Glucose and amino acids may be filtered together with urea and uric acid.

B. Tubular reabsorption selectively returns useful substances to the blood.

C. Glomerular filtration is selective because it filters wastes separately from nutrients.

D. Glomerular filtration excludes useful substances while allowing metabolic wastes through.

E. Water and minerals can enter Bowman's capsule during the filtration process.

Answer: (A), (B), (E)

Explanation

Glomerular filtration is non-selective: glucose, amino acids, vitamins, minerals, and water are filtered together with wastes. Selective recovery of useful substances occurs later during tubular reabsorption.

13. Regarding proximal convoluted tubule reabsorption, which statement is accurate?

A. Glucose and amino acids return to blood through active reabsorption.

B. Vitamins are secreted from peritubular capillaries into the proximal tubule.

C. About 65% of filtered water returns to blood by osmosis.

D. Important nutrients remain in the tubular fluid for later excretion.

E. Water returns to blood through active transport requiring cellular pumps.

Answer: (A), (C)

Explanation

In the proximal convoluted tubule, glucose, amino acids, vitamins, and other important substances are actively reabsorbed. Approximately 65% of water returns to the blood passively by osmosis.

14. Concerning the ascending loop of Henle, which statement is correct?

A. Its water impermeability contributes to medullary hypertonicity.

B. Its cells allow water to leave freely while retaining salts.

C. It passively removes sodium ions without affecting medullary concentration.

D. It actively pumps salt into the medulla.

E. It establishes a steep water-potential gradient in the medulla.

Answer: (A), (D), (E)

Explanation

The ascending loop of Henle is impermeable to water and actively pumps salt into the medulla. This makes the medulla hypertonic and establishes a steep water-potential gradient.

15. Which pathway correctly describes urine movement after collection in the kidney?

A. The urethra carries urine from the bladder outside the body.

B. Collecting ducts, renal pelvis, urethra, bladder, then ureter.

C. The renal pelvis receives urine after it has passed through the ureter.

D. The ureter carries urine from the kidney to the bladder.

E. Collecting ducts, renal pelvis, ureter, bladder, then urethra.

Answer: (A), (D), (E)

Explanation

Urine moves from collecting ducts to the renal pelvis, through a ureter to the bladder, and exits through the urethra. The ureter therefore connects the kidney to the bladder, whereas the urethra carries urine out of the body.

16. The normal composition and handling of urine include:

A. Useful substances are normally reabsorbed rather than excreted.

B. Urea is a normal component of urine.

C. Excess water can be eliminated in urine.

D. Excess salts may be eliminated in urine.

E. Glucose and amino acids normally form the principal useful contents of urine.

Answer: (A), (B), (C), (D)

Explanation

Urine contains urea, excess water, and excess salts. Useful substances are normally reabsorbed and therefore should not be excreted as normal urine components.

17. Regarding renal pH regulation, which statements are correct?

A. Renal regulation returns blood pH toward $7.0$.

B. Low blood pH is associated with an increased hydrogen-ion concentration.

C. Low blood pH is associated with excess bicarbonate ions.

D. Hydrogen ions move from peritubular capillaries into the distal convoluted tubule.

E. Hydrogen ions move from the distal convoluted tubule into peritubular capillaries.

Answer: (B), (D)

Explanation

Low blood pH reflects an increased hydrogen-ion concentration, and hydrogen ions move from peritubular capillaries into the distal convoluted tubule. This renal response moves blood pH back toward $7.4$; excess bicarbonate is associated with high rather than low pH.

18. A patient has a low blood pH caused by excess hydrogen ions. Which renal responses are expected?

A. Blood pH moves toward approximately $7.4$.

B. Hydrogen ions enter the distal convoluted tubule from peritubular capillaries.

C. Hydrogen ions are transferred from the tubule into peritubular capillaries.

D. Excess bicarbonate is identified as the cause of the low blood pH.

E. Blood pH moves toward approximately $6.4$.

Answer: (A), (B)

Explanation

Hydrogen ions are transferred from peritubular capillaries into the distal convoluted tubule when blood pH is low. Low pH results from excess hydrogen ions, whereas excess bicarbonate is associated with high blood pH and the regulated value approaches $7.4$.

19. Osmoregulation is best described by which statements?

A. It is the homeostatic control of dissolved salt levels in body fluids.

B. It describes sodium reabsorption from filtrate into blood.

C. It regulates hydrogen-ion concentration in the distal convoluted tubule.

D. It is the homeostatic control of water levels in blood and tissue fluid.

E. It concerns water levels in both blood and tissue fluid.

Answer: (D)

Explanation

Osmoregulation maintains water levels in blood and tissue fluid. Dissolved salt levels belong to salt regulation, while the other propositions assign osmoregulation to salt or acid-base control.

20. Concerning ADH, which statements are correct?

A. ADH is produced by the hypothalamus and secreted by the pituitary gland.

B. ADH decreases water permeability in the collecting ducts.

C. ADH is produced by the pituitary gland and secreted by the hypothalamus.

D. ADH increases water permeability in the distal convoluted tubule and collecting ducts.

E. ADH reduces water loss in urine by increasing tubular water permeability.

Answer: (A), (D), (E)

Explanation

ADH is produced by the hypothalamus and secreted by the pituitary gland. It increases water permeability in the distal convoluted tubule and collecting ducts, thereby reducing urinary water loss; reduced ADH has the opposite permeability effect.

21. A person shifts from dehydration to overhydration. Which statements correctly describe the resulting ADH-related changes?

A. Dehydration reduces ADH and produces a larger volume of dilute urine.

B. Overhydration produces a larger volume of dilute urine.

C. Dehydration increases ADH release and promotes greater water reabsorption.

D. Dehydration produces a smaller volume of concentrated urine.

E. Overhydration reduces ADH and promotes less water reabsorption.

Answer: (B), (C), (D), (E)

Explanation

During dehydration, increased ADH promotes greater water reabsorption and produces a smaller volume of concentrated urine. During overhydration, reduced ADH decreases reabsorption and produces more dilute urine; the other statements reverse or misattribute these effects.

22. When blood sodium levels fall, which responses are expected?

A. Aldosterone reduces sodium excretion in urine.

B. Aldosterone stimulates sodium reabsorption from filtrate into blood.

C. The pituitary gland releases aldosterone in response to low blood sodium.

D. Aldosterone stimulates hydrogen-ion excretion instead of sodium reabsorption.

E. The adrenal gland releases aldosterone in response to low blood sodium.

Answer: (A), (B), (E)

Explanation

Low blood sodium stimulates the adrenal gland to release aldosterone. Aldosterone increases sodium reabsorption from filtrate into blood and consequently reduces sodium excretion; it is not secreted by the pituitary gland or directed toward hydrogen-ion removal.