Biology

Human Excretion and Kidney Physiology

1,215 Questions

Human excretion and kidney physiology questions test your understanding of the excretory system, including the role of renal tubules and glomerular filtration. You will also find topics on urine formation, body water absorption, and excretory products. This section is vital for medical and general science exam preparation.

Glomerular filtrationRenal tubule absorptionExcretory productsRole of sodium ionsHuman excretory system

Human Excretion and Kidney Physiology Questions

Multiple choice

Which of the following statements concerning the bicarbonate ions in the kidney tubule is INCORRECT?

  1. Bicarbonate ions are freely filtered in the glomerulus.

  2. Bicarbonate ions are reabsorbed in the distal tubule.

  3. Carbonic anhydrase catalyses the formation of bicarbonate ions.

  4. The secretion of hydrogen ions results in bicarbonate reabsorption.

  5. If required, the bicarbonate ions can function as a base in the kidneys.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The major site of reabsorption of bicarbonate ions is the proximal tubule.

Multiple choice

Which of the following statements characterises the excretion of acid by the nephron?

  1. Acid can be excreted as NH4+ ions.

  2. Acid excretion mainly occurs in the early nephron.

  3. In the distal nephron, secreted hydrogen ions mainly contribute to bicarbonate reabsorption.

  4. Sodium phosphate is a urinary base.

  5. Human urine is usually alkaline in nature.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When hydrogen ions are secreted by the tubules, they can combine with NH3 to form NH4+ and excreted as NH4+.

Multiple choice

Which of the following statements regarding calcium and phosphate ions in the body is INCORRECT?

  1. Calcium is the major cation in extracellular fluid.

  2. A rise in plasma calcium levels can cause precipitation of calcium phosphate.

  3. Intracellular calcium concentration is tightly regulated.

  4. The calcium in plasma also exists as complexes with other ions such as phosphate.

  5. A rise in plasma phosphate levels can cause precipitation of calcium phosphate.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Calcium is the major divalent cation in the body. But most of this calcium is present in bone. Sodium is the major cation in extracellular fluid. In extracellular fluid, the concentration of sodium is around 135-145mMol/l whereas the concentration of calcium is around 2.25mM, of which about half is protein bound.

Multiple choice

Which of the following statements concerning the renal excretion of drugs is INCORRECT?

  1. Tubular secretion is more important than tubular reabsorption for most of the drugs.

  2. Drug molecules, which are bound to proteins are not filtered.

  3. Lipid soluble drugs require special transporter molecules to cross cell membranes.

  4. The proximal tubule is a site of drug secretion.

  5. A charge on a drug favours water solubility.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Lipid soluble drugs and other lipid soluble substances are able to diffuse across the lipid plasma membrane of cells without special transporter molecules.

Multiple choice

Which of the following statements regarding renal reabsorption of calcium and phosphate is FALSE?

  1. Calcium is reabsorbed but not secreted in the tubules.

  2. Phosphate is secreted but not reabsorbed in the tubules.

  3. Phosphate is reabsorbed with sodium in the proximal tubule.

  4. Calbindins can transport calcium across tubular cells.

  5. The reabsorption of calcium and phosphate ions takes place in the proximal tubules.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

There is no secretion of phosphate and is reabsorbed along the nephron. There is a limit to the amount of phosphate that can be absorbed and if this limit exceeds, the excess phosphate remains in the tubular fluid and is excreted in the urine.

Multiple choice

Which of the following statements regarding water balance by the kidney is CORRECT?

  1. Aquaporin is the main hormone regulating water reabsorption.

  2. The key hormone regulating water reabsorption is secreted from the anterior pituitary gland.

  3. The vasa recta has the same structure as the Loop of Henle.

  4. There are osmoreceptors in the hypothalamus.

  5. There is no limit to how much the body can concentrate the urine.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There are osmoreceptors in the hypothalamus, which detect an increase in plasma osmolality. In response to input from these receptors and other stimuli, cells in the posterior pituitary gland release ADH.

Multiple choice

Which of the following statements characterises the renal blood flow in humans?

  1. The efferent arterioles deliver blood to the glomerulus.

  2. Vasa recta receive their blood supply from the afferent arterioles.

  3. Vasoconstriction of afferent arterioles increases glomerular filtration.

  4. Vasoconstriction of the efferent arterioles increases glomerular filtration.

  5. Vasoconstriction reduces the resistance to flow in a blood vessel.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

If there is vasoconstriction of the efferent arteriole, the pressure upstream the constriction in the glomerulus is increased and so more filtration occurs.

Multiple choice

Which of the following does not cause vasoconstriction in the kidneys?

  1. Angiotensin II

  2. Vasopressin

  3. Epinephrine

  4. Non-steroidal anti-inflammatory drugs

  5. Prostaglandins
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Non-steroidal anti-inflammatory drugs block prostaglandin synthesis and so remove this tonic dilatation. The result is renal vasoconstriction. Prostaglandins are powerful vasodilators and there is a normal tonic level of vasodilation in the renal blood vessels, which is caused by prostaglandins.

Multiple choice

Which of the following statements is true regarding sodium ions absorption in the kidneys?

  1. The concentration of sodium ions is generally higher inside the cells than outside .

  2. The amount of sodium in the initial filtrate is much less than that in the plasma.

  3. Most sodium is reabsorbed in the distal tubule.

  4. There is no active transport of sodium.

  5. The diuretic drug furosemide blocks the Na-K-2Cl channel in the loop of Henle.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Diuretics such as furosemide inhibits sodium reabsorption in the loop of Henle by blocking the Na-K-2Cl channel in the loop of Henle. Drugs such as the thiazides oppose sodium reabsorption in the distal tubule.

Multiple choice

After the investigation, doctor told Amit that he was suffering from renal artery stenosis. Which of the following tests must have been done by the doctor?

  1. Ultrasound scanning

  2. Measurement of the creatinine clearance

  3. Measurement of protein loss in the urine

  4. Renal angiography

  5. Renal biopsy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Renal angiography involves the injection of a radio opaque dye into the renal vessels while x-ray images are taken of the vessels. Using this approach, it is possible to identify stenoses or narrowings in the renal arteries.

Multiple choice

Potassium secretion occurs only in______________.

  1. principal cells of the collecting duct

  2. glomerulus

  3. loop of Henle

  4. the intercalated cells of collecting duct

  5. proximal tubule
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Potassium secretion occurs only from the principal cells of the collecting duct. It is this potassium secretion, which is used to control potassium excretion.

Multiple choice

Regarding the clinical assessment of patients with suspected renal disease, which of the following statements is true?

  1. Peripheral edema suggests volume depletion.

  2. Bruits heard over the renal arteries suggest renal artery stenosis.

  3. Dipstick testing of urine is an ineffective technique.

  4. Measuring blood pressure is unnecessary.

  5. A drug history can be safely omitted.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Renal artery stenosis describes narrowings of the renal arteries.When there is such a narrowing, turbulent flow through the narrowing can produce a noise known as a bruit. This is important because the narrowing can reduce the blood supply to the kidney and thus can damage the kidney.

Multiple choice

Which of the following statements is true regarding potassium ion in the kidneys?

  1. Potassium is the major extracellular ion.

  2. Within cells, the concentration of potassium is lower than that of sodium.

  3. Potassium excretion is regulated by altering potassium secretion.

  4. The 3Na+/2K+ ATPase pumps potassium out of cells.

  5. Specialised cells have potassium channels.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Potassium is freely filtered and then most of the filtered potassium is reabsorbed. Potassium excretion is then controlled by the secretion of potassium by the principal cells in the collecting ducts. 

Multiple choice

Which of the following transporter molecules exchanges sodium for hydrogen ions in the proximal tubule of the kidneys?

  1. Na-K--2Cl

  2. ROMK

  3. 3Na+/2K+ ATPase

  4. NHE 3

  5. ENaC
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The NHE 3 is a counter transporter that exchanges sodium ions in the tubular fluid for hydrogen ions from the cell. This is a passive process, which like sodium reabsorption in most other tubular cells, occurs along the sodium concentration gradient which has been created by the 3Na+/2K+ ATPase.

Multiple choice

Which of the following statements is true regarding acid base regulation in the body?

  1. Overall human metabolism results in acid production .

  2. Buffers present in kidneys must be strong acids or bases.

  3. Carbon dioxide directly raises the pH of body fluids.

  4. The pH of a buffer solution is always 7.

  5. A rise in the plasma level of bicarbonate ions lowers the pH of plasma.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Overall the body is a net producer of acid, and a major function of the kidney is to excrete this acid load.