Saliva and Secretion Control
1.Which of the following are NOT correctly matched?
A) Lysozyme: enzyme that attacks bacterial cell walls
B) Lactoferrin: binds iron, restricting its availability to microorganisms
C) Statherin: reduces calcium concentration in the oral cavity to prevent precipitation
D) Histatin: anti-fungal protein in saliva
C) Statherin: reduces calcium concentration in the oral cavity to prevent precipitation
.Which of the following best describes the digestion and absorption of proteins in the small intestine?
A) Proteins are primarily absorbed in the stomach, with pepsin breaking them down into amino acids before they are absorbed by receptor-mediated endocytosis.
B) Most ingested proteins are digested by pancreatic proteases in the small intestine, and small peptides are absorbed via a proton-dependent transport system (PepT1).
C) Absorption of proteins occurs mainly in the duodenum, where amino acids are absorbed by specific sodium-independent transporters and transported into the bloodstream.
D) Proteins are mostly digested by enzymes in the stomach, while the small intestine only absorbs small amounts of peptides and amino acids through diffusion.
E) Proteins are absorbed as intact molecules by enterocytes in the jejunum, where they are broken down into amino acids after absorption.
B) Most ingested proteins are digested by pancreatic proteases in the small intestine, and small peptides are absorbed via a proton-dependent transport system (PepT1).
What happens to the glucose reabsorption mechanism in cases of hyperglycemia, such as in diabetes mellitus?
A. The SGLT1 transporter upregulates its activity to handle the increased glucose load.
B. Glucose appears in the urine because the transporters saturate, exceeding the Tm.
C. GLUT2 activity decreases at the basolateral membrane, limiting glucose efflux.
D. Glucose is secreted into the tubular lumen to maintain homeostasis.
B. Glucose appears in the urine because the transporters saturate, exceeding the Tm.
Which of the following is a key difference between esophageal and stomach peristalsis?
a) Esophageal peristalsis involves both skeletal and smooth muscles, while stomach peristalsis involves only smooth muscles.
b) Stomach peristalsis is faster than esophageal peristalsis.
c) Esophageal peristalsis is influenced by gastric hormones, while stomach peristalsis is not.
d) Stomach peristalsis is voluntary, while esophageal peristalsis is involuntary.
a) Esophageal peristalsis involves both skeletal and smooth muscles, while stomach peristalsis involves only smooth muscles.
Which of the following scenarios would most likely result in the secretion of antidiuretic hormone (ADH)?
A. Increased plasma osmolality and decreased blood volume
B. Decreased plasma osmolality and increased blood volume
C. Increased atrial natriuretic peptide (ANP) levels
D. Elevated renal perfusion pressure
A. Increased plasma osmolality and decreased blood volume
2. Which of the following best describes the neural regulation of salivary secretion?
A) Parasympathetic stimulation is the primary driver of saliva secretion, enhancing fluid and electrolyte production through vasoactive intestinal polypeptide (VIP) and kallikrein release.
B) Sympathetic stimulation is much more effective than parasympathetic stimulation in increasing salivary secretion, particularly through the activation of alpha- and beta-receptors.
C) Parasympathetic and sympathetic stimulation both increase saliva production, with parasympathetic stimulation producing more fluid and electrolyte secretion, while sympathetic stimulation mainly increases amylase and mucous secretion.
D) Sympathetic stimulation decreases the production of saliva, causing vasoconstriction in the salivary glands and reducing secretion of fluids and electrolytes.
E) Parasympathetic stimulation causes vasodilation, leading to decreased blood flow and reduced salivation during the digestion process.
C) Parasympathetic and sympathetic stimulation both increase saliva production, with parasympathetic stimulation producing more fluid and electrolyte secretion, while sympathetic stimulation mainly increases amylase and mucous secretion.
Which of the following statements best explains the defects in amino acid absorption and their potential clinical consequences?
A) Defects in amino acid transporters in enterocytes result in malnutrition, as these transporters are critical for amino acid absorption.
B) Inherited disorders affecting specific amino acid transporters may result in the presence of amino acids in the urine, but these conditions do not lead to malnutrition due to peptide absorption.
C) Defects in amino acid transporters lead to poor absorption of both dipeptides and amino acids, causing a significant protein deficiency in the body.
D) Disorders of amino acid transporters result in decreased absorption of small peptides, which causes malnutrition since amino acids cannot be absorbed by any other means.
E) Defects in the renal tubule transporters exclusively lead to amino acids in the urine but do not affect amino acid absorption in the intestine.
B) Inherited disorders affecting specific amino acid transporters may result in the presence of amino acids in the urine, but these conditions do not lead to malnutrition due to peptide absorption.
Which of the following correctly describes the mechanism of sodium reabsorption at the proximal tubule?
A. Sodium is reabsorbed via cotransport with chloride in the early proximal tubule.
B. Sodium enters the cells through the NKCC2 cotransporter and exits using GLUT1.
C. Sodium is cotransported with organic solutes like glucose and amino acids in the early proximal tubule.
D. Sodium reabsorption is independent of Na+-K+ ATPase activity in the proximal tubule
C. Sodium is cotransported with organic solutes like glucose and amino acids in the early proximal tubule.
A 50-year-old patient presents with difficulty swallowing (dysphagia) and reports regurgitation of undigested food. Esophageal manometry (measures pressure in GI) reveals impaired peristaltic waves in the esophagus. Which of the following best distinguishes esophageal peristalsis from stomach peristalsis in normal physiology?
a) Esophageal peristalsis is controlled exclusively by the myenteric plexus, while stomach peristalsis requires input from the central nervous system.
b) Esophageal peristalsis is rapid and solely propels food, while stomach peristalsis is slower and also mixes food with digestive enzymes.
c) Both esophageal and stomach peristalsis rely on pacemaker cells to initiate contraction waves.
d) Stomach peristalsis occurs only after food enters the duodenum, while esophageal peristalsis begins before swallowing.
a) Esophageal peristalsis is controlled exclusively by the myenteric plexus, while stomach peristalsis requires input from the central nervous system.
A 45-year-old patient with a history of chronic kidney disease (CKD) develops severe hyperkalemia. To address this, he is given an aldosterone agonist to promote potassium excretion.
Question:
Which of the following nephron sites will show increased activity in response to the aldosterone agonist?
A. Proximal tubule
B. Thick ascending limb of Henle's loop
C. Distal convoluted tubule and collecting duct
D. Thin descending limb of Henle's loop
C. Distal convoluted tubule and collecting duct
3. Which of the following best describes the process by which water and electrolytes are secreted in the salivary glands?
A) Primary secretion in acinar cells is similar to plasma, but as the fluid passes through the ducts, Na+ and Cl- are reabsorbed while K+ and HCO3- are secreted, making the saliva hypotonic.
B) The acinar cells secrete a fluid that is similar to plasma, which is then modified in the ducts to produce isotonic saliva through passive ion reabsorption.
C) Saliva is always isotonic, as Na+ and Cl- are actively secreted into the lumen, and the ducts reabsorb water in an equal proportion to maintain osmotic balance.
D) The ducts are permeable to both water and ions, resulting in isotonic saliva that contains equal amounts of Na+ and Cl- at all flow rates.
E) Water is secreted passively by the acinar cells, while electrolyte composition in the saliva is maintained by a hormonal feedback mechanism involving aldosterone
A) Primary secretion in acinar cells is similar to plasma, but as the fluid passes through the ducts, Na+ and Cl- are reabsorbed while K+ and HCO3- are secreted, making the saliva hypotonic.
All of the following contribute to the absorption of water and electrolytes in the intestines EXCEPT:
A. Osmotic water flow from the lumen into intercellular spaces driven by Na+ reabsorption
B. Na+-coupled entry of glucose, galactose, and amino acids enhancing Na+ absorption in the jejunum
C. Secretion of Cl- ions into the lumen to maintain osmotic balance
D. Paracellular absorption of Cl- driven by the electrical potential difference created by Na+ absorption
E. Stimulation of Na+ absorption in the colon by aldosterone
C. Secretion of Cl- ions into the lumen to maintain osmotic balance
A 60-year-old man presents with high blood pressure and hypokalemia. His condition is found to be due to an overproduction of aldosterone. How does aldosterone affect sodium and potassium handling in the nephron?
A. Increases sodium reabsorption and potassium secretion in the collecting duct.
B. Increases sodium reabsorption and decreases potassium reabsorption in the proximal tubule.
C. Decreases sodium reabsorption and increases potassium secretion in the distal tubule.
D. Enhances sodium secretion and potassium reabsorption in the thick ascending limb.
A. Increases sodium reabsorption and potassium secretion in the collecting duct.
Which of the following accurately describes how the kidney handles glucose?
a) Glucose is secreted into the tubular lumen at the proximal tubule if plasma glucose exceeds the renal threshold.
b) Glucose is reabsorbed via sodium-glucose cotransporters (SGLTs) in the proximal tubule until transporters become saturated.
c) The distal tubule reabsorbs glucose under hormonal regulation.
d) The kidneys cannot filter glucose due to its size and polarity
b) Glucose is reabsorbed via sodium-glucose cotransporters (SGLTs) in the proximal tubule until transporters become saturated.
A 35-year-old woman is admitted for severe dehydration following a marathon. Labs reveal serum sodium of 155 mEq/L, plasma osmolality of 310 mOsm/kg, and a urine osmolality of 1,200 mOsm/kg.
Question:
Which renal mechanism is responsible for the patient’s concentrated urine?
A. Decreased activity of the sodium-potassium-chloride transporter in the thick ascending limb
B. Increased permeability of the collecting duct to water due to high ADH levels
C. Enhanced proximal tubular sodium reabsorption
D. Elevated glomerular filtration rate (GFR) promoting sodium excretion
B. Increased permeability of the collecting duct to water due to high ADH levels
4. Which of the following best describes the process of gastric acid secretion and its regulation?
A) The parietal cell secretes HCl via a Na+/H+ exchanger, and this process is regulated solely by acetylcholine and gastrin.
B) Gastric acid is secreted by parietal cells through the H+/K+ ATPase pump, which is activated by histamine, acetylcholine, and gastrin. Bicarbonate is transported across the basolateral membrane, creating an alkaline tide.
C) Parietal cells secrete HCl through a passive transport mechanism, and gastric acid secretion is mainly controlled by the D-cell secretion of somatostatin.
D) The ECL cell secretes histamine, which directly stimulates parietal cells to secrete HCl, while gastrin indirectly activates parietal cells via the CCK-2 receptor.
E) The parietal cell secretes HCl directly into the bloodstream, and the release of gastrin is inhibited when the pH of chyme is higher than 7.
B) Gastric acid is secreted by parietal cells through the H+/K+ ATPase pump, which is activated by histamine, acetylcholine, and gastrin. Bicarbonate is transported across the basolateral membrane, creating an alkaline tide.
All of the following statements about sodium (Na+) reabsorption in the nephron are correct EXCEPT:
A) About two-thirds of the filtered Na+ and water are reabsorbed in the proximal tubule, where Na+ is transported via cotransport with organic solutes and through the Na+/H+ exchanger.
B) The thick ascending limb (TAL) of the loop of Henle reabsorbs Na+ through the NKCC2 cotransporter, which moves Na+, K+, and Cl- in a 1:1:2 ratio and is sensitive to loop diuretics.
C) In the early distal tubule, Na+ reabsorption occurs through an Na+/Cl- cotransporter (NCC), which is sensitive to thiazide diuretics.
D) The descending limb of the loop of Henle has high permeability to Na+, allowing for passive Na+ reabsorption along the concentration gradient.
E) Na+ entry in the late distal tubule and collecting duct occurs via the epithelial Na+ channel (ENaC), which is sensitive to amiloride and upregulated by aldosterone.
D) The descending limb of the loop of Henle has high permeability to Na+, allowing for passive Na+ reabsorption along the concentration gradient.
A patient with dehydration presents with concentrated urine and a low urine output. ADH levels are elevated. Which of the following mechanisms explains the action of ADH in this scenario?
A. Stimulation of aquaporin-2 insertion in the proximal tubule.
B. Increased reabsorption of water in the descending limb of Henle’s loop.
C. Enhancement of water reabsorption in the collecting duct via aquaporin-2 channels.
D. Decreased osmolarity of the renal medulla to facilitate water reabsorption.
C. Enhancement of water reabsorption in the collecting duct via aquaporin-2 channels.
A 45-year-old patient with poorly controlled diabetes mellitus presents with polyuria and fatigue. Laboratory testing reveals a fasting plasma glucose level of 250 mg/dL, normal levels should be (80-100 mg/dL). Which of the following best explains why glucose is present in the patient’s urine?
a) Increased glomerular filtration rate (GFR) causes glucose to bypass reabsorption.
b) Saturation of sodium-glucose cotransporters (SGLTs) in the proximal tubule.
c) Impaired function of GLUT transporters in the collecting duct.
d) Overactivation of the Na+/K+/2Cl− cotransporter (NKCC2) in the loop of Henle
b) Saturation of sodium-glucose cotransporters (SGLTs) in the proximal tubule.
In a patient with congestive heart failure (CHF), which observation is expected regarding the effective circulating volume (ECV) and extracellular fluid (ECF)?
A. Increased ECV and decreased ECF
B. Decreased ECV and increased ECF
C. Increased ECV and ECF
D. Decreased ECV and ECF
B. Decreased ECV and increased ECF
5. Which of the following best describes the activation of pancreatic enzymes and the regulation of pancreatic secretion?
A) Pancreatic enzymes are secreted in their active forms, with trypsinogen being activated by enteropeptidase in the duodenum. Cholecystokinin (CCK) stimulates secretion of enzyme-rich fluid, while secretin induces bicarbonate secretion from duct cells.
B) Pancreatic proteases, including trypsin, are secreted as proenzymes and are activated in the duodenum by enteropeptidase. Cholecystokinin stimulates acinar cells to release enzymes, and secretin stimulates duct cells to release bicarbonate-rich fluid.
C) Pancreatic enzymes are synthesized in the pancreas as active enzymes, and their activation occurs in the stomach. Secretin stimulates enzyme-rich fluid from acinar cells, while CCK enhances bicarbonate secretion.
D) Enteropeptidase activates trypsinogen to trypsin, which then activates the other pancreatic enzymes. Cholecystokinin (CCK) stimulates bicarbonate secretion, and secretin acts mainly on acinar cells to increase enzyme secretion.
E) Trypsinogen is converted to active trypsin in the stomach, where it activates other enzymes. Secretin stimulates pancreatic acinar cells to release enzymes, while CCK induces bicarbonate secretion from duct cells.
B) Pancreatic proteases, including trypsin, are secreted as proenzymes and are activated in the duodenum by enteropeptidase. Cholecystokinin stimulates acinar cells to release enzymes, and secretin stimulates duct cells to release bicarbonate-rich fluid.
Which of the following are NOT correctly matched?
A) Enteropeptidase: initiates activation of pancreatic enzymes at the brush border of the small intestine
B) PepT1: responsible for proton-dependent transport of dipeptides and tripeptides across the apical membrane
C) Pancreatic acinar cells: secretion of trypsinogen, chymotrypsinogen, and proelastase into the duodenum
D) Basolateral membrane of enterocytes: primary site of peptidase activity for hydrolyzing di- and tripeptides
D) Basolateral membrane of enterocytes: primary site of peptidase activity for hydrolyzing di- and tripeptides
Which statement about the clearance principle and its application to estimate renal function is true?
A. Clearance of inulin underestimates GFR because it is partially reabsorbed.
B. Creatinine clearance is higher than GFR in humans due to partial tubular secretion of creatinine[SC1] .
C. The clearance of para-aminohippurate (PAH) is used to estimate GFR because PAH is freely filtered and completely reabsorbed.
D. Clearance values for all substances decrease proportionally in renal failure.
B. Creatinine clearance is higher than GFR in humans due to partial tubular secretion of creatinine
Which of the following factors increases potassium secretion in the distal nephron?
a) Low dietary potassium intake.
b) High aldosterone levels.
c) Increased activity of the Na+/K+/2Cl− cotransporter (NKCC2) in the thick ascending limb.
d) Decreased tubular flow rate in the collecting duct.
b) High aldosterone levels.
Which factor does not directly stimulate renin release from the juxtaglomerular apparatus?
A. Decreased sodium delivery to the macula densa
B. Increased atrial natriuretic peptide secretion
C. Sympathetic nervous system activation
D. Reduced perfusion pressure in the afferent arterioles
B. Increased atrial natriuretic peptide secretion