Evaluate the statements regarding the sphincters in the human alimentary canal and choose the correct option:
I. The gastro-oesophageal sphincter regulates the opening of the oesophagus into the stomach. II. The pyloric sphincter guards the opening of the stomach into the duodenum. III. The sphincter of Oddi guards the common hepato-pancreatic duct opening into the duodenum. IV. The ileo-caecal valve allows the backflow of faecal matter from the colon to the ileum.
Explanation: Statements I, II, and III are correct. The gastro-oesophageal sphincter regulates entry into the stomach, the pyloric sphincter regulates gastric emptying, and the sphincter of Oddi guards the common hepato-pancreatic duct. Statement IV is incorrect because the ileo-caecal valve prevents backflow of faecal matter.
Question 32 of 100
📘 CLASS XI
Read the following statements about the histology of the alimentary canal wall from oesophagus to rectum:
I. The correct sequence of layers from the outermost to the innermost is Serosa, Muscularis, Sub-mucosa, and Mucosa. II. Serosa is made up of a thin mesothelium (epithelium of visceral organs) with some connective tissues. III. Muscularis is usually arranged into an inner longitudinal and an outer circular layer. IV. The sub-mucosal layer is formed of loose connective tissues containing nerves, blood, and lymph vessels.
Explanation: Statements I, II, and IV are correct. The wall of the alimentary canal consists of serosa, muscularis, submucosa, and mucosa from outside to inside. Serosa contains mesothelium and connective tissue, while the submucosa contains loose connective tissue with nerves, blood vessels, and lymph vessels. Statement III is incorrect because the muscularis consists of an inner circular and an outer longitudinal muscle layer.
Question 33 of 100
📘 CLASS XI
Read the following statements regarding the modifications of mucosa in the small intestine:
I. Villi are small finger-like foldings formed by the mucosa of the small intestine. II. The cells lining the villi have microscopic projections called microvilli which increase surface area enormously. III. Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal. IV. Lacteals are primarily involved in the absorption of amino acids and simple sugars.
Explanation: Statements I, II, and III are correct as they describe the structural anatomy of the intestinal villi and microvilli. Statement IV is incorrect because lacteals primarily absorb fats in the form of chylomicrons, whereas amino acids and simple sugars are absorbed into the blood capillaries.
Question 34 of 100
📘 CLASS XI
Identify the correct set of statements regarding the exocrine secretion of the pancreas:
I. Pancreatic juice contains inactive enzymes: trypsinogen, chymotrypsinogen, and procarboxypeptidases. II. It also contains active enzymes like amylases, lipases, and nucleases. III. Pancreatic juice is highly acidic to help in the digestion of proteins. IV. Trypsinogen is activated by enterokinase, which is a pancreatic exocrine enzyme.
Explanation: Statements I and II are correct because pancreatic juice contains inactive proteolytic enzymes along with active amylase, lipase, and nucleases. Statement III is incorrect because pancreatic juice is alkaline. Statement IV is incorrect because enterokinase is secreted by the intestinal mucosa, not the pancreas.
Question 35 of 100
📘 CLASS XI
Read the following statements about the activation of proteolytic enzymes in the small intestine:
I. Trypsinogen is converted to active trypsin by enterokinase. II. Active trypsin then autocatalytically activates more trypsinogen. III. Trypsin activates chymotrypsinogen into chymotrypsin and procarboxypeptidase into carboxypeptidase. IV. Enterokinase is secreted directly by the exocrine cells of the liver into the bile.
Explanation: Statements I, II, and III are correct because trypsin is the central activating enzyme for pancreatic proteases. Statement IV is incorrect because enterokinase is secreted by the intestinal mucosa, not by the liver.
Question 36 of 100
📘 CLASS XI
Which of the following statements regarding the composition and function of bile juice is/are correct?
I. Bile contains bile pigments (bilirubin and biliverdin), bile salts, cholesterol, and phospholipids. II. Bile contains inactive lipases which are activated by pancreatic trypsin. III. Bile helps in the emulsification of fats into very small micelles. IV. Bile contains no digestive enzymes.
Explanation: Statements I, III, and IV are correct. Bile contains bile pigments, bile salts, cholesterol, and phospholipids but no digestive enzymes. It emulsifies fats into tiny micelles and facilitates lipase action. Statement II is incorrect because bile contains no enzymes.
Question 37 of 100
📘 CLASS XI
Analyze the following statements regarding the intestinal juice (succus entericus) and choose the correct combination:
I. It is formed by the secretions of mucosal brush border cells and mucosal goblet cells. II. It contains enzymes like maltase, dipeptidases, lipases, and nucleosidases. III. Succus entericus contains nucleases that break down DNA and RNA into nucleotides. IV. The mucus and bicarbonates in succus entericus help provide an alkaline pH of 7.8.
Explanation: Statements I, II, and IV are correct. Succus entericus is formed from brush border and goblet cell secretions and contains digestive enzymes including disaccharidases, peptidases, lipases, nucleotidases, and nucleosidases. Statement III is incorrect because nucleases are pancreatic enzymes.
Question 38 of 100
📘 CLASS XI
Evaluate the statements regarding Brunner's glands and Crypts of Lieberkuhn and identify the correct set:
I. Brunner's glands are located in the sub-mucosa of the duodenum. II. Crypts of Lieberkuhn are mucosal pits present between the bases of villi in the intestine. III. Brunner's glands secrete mucus and bicarbonates to protect the duodenum from acidic chyme. IV. Crypts of Lieberkuhn are present only in the stomach mucosa.
Explanation: Statements I, II, and III are correct. Brunner's glands occur in the duodenal submucosa and secrete alkaline mucus, while Crypts of Lieberkuhn are intestinal glands located between villi. Statement IV is incorrect because Crypts of Lieberkuhn are found in the intestinal mucosa, not in the stomach.
Question 39 of 100
📘 CLASS XI
Read the following statements about protein digestion in the human small intestine and select the correct combination:
I. Trypsin, chymotrypsin, and carboxypeptidase are exocrine pancreatic enzymes that act on partially digested proteins. II. Proteins, peptones, and proteoses are converted into dipeptides by pancreatic proteases. III. Dipeptides are converted into amino acids by dipeptidases of the pancreatic juice. IV. Pepsin continues to digest proteins at pH 7.8 in the small intestine.
Explanation: Statements I and II are correct. Statement III is incorrect because dipeptidases are enzymes of the succus entericus (intestinal juice), not pancreatic juice. Statement IV is incorrect because pepsin is active only in the highly acidic environment of the stomach (around pH 1.8) and is inactivated in the alkaline pH of the small intestine.
Question 40 of 100
📘 CLASS XI
Evaluate the statements regarding carbohydrate digestion in the human body and choose the correct combination:
I. Digestion of starch begins in the mouth, where about 30% of it is hydrolysed by salivary amylase. II. The acidic environment of the stomach completely halts carbohydrate digestion. III. Pancreatic amylase digests polysaccharides (starch) into disaccharides in the small intestine. IV. Maltase, lactase, and sucrase in the succus entericus convert disaccharides into monosaccharides.
Explanation: All four statements are correct. Salivary amylase begins starch digestion in the oral cavity and hydrolyses about 30% of starch. Its activity stops in the acidic stomach. Pancreatic amylase continues digestion in the small intestine, while intestinal disaccharidases convert disaccharides into monosaccharides.
