Digestive System Question Paper

Subject: Biology
Topic: Digestive System
Total Marks: 350
Time: 3 Hours

Section A: Multiple Choice Questions (MCQs) - 100 Questions × 1 Mark = 100 Marks

Instructions: Choose the correct answer from the given options.

The digestive system is primarily responsible for: a) Circulation of blood b) Breaking down food into smaller molecules c) Gas exchange d) Waste filtration
Which enzyme in saliva begins carbohydrate digestion? a) Pepsin b) Lipase c) Amylase d) Trypsin
The wave-like muscular contractions that move food through the esophagus are called: a) Peristalsis b) Churning c) Segmentation d) Mastication
Gastric juices contain: a) Only hydrochloric acid b) Only pepsin c) Hydrochloric acid and pepsin d) Bile and amylase
The semi-liquid paste formed in the stomach is called: a) Bolus b) Chyme c) Feces d) Bile
The primary site for nutrient absorption is: a) Stomach b) Large intestine c) Small intestine d) Mouth
Which organ produces bile? a) Pancreas b) Liver c) Gallbladder d) Stomach
Pepsin is activated by: a) Bile b) Pancreatic juice c) Hydrochloric acid d) Saliva
The function of the large intestine is primarily: a) Protein digestion b) Fat emulsification c) Water and electrolyte absorption d) Carbohydrate breakdown
Feces are stored in the: a) Rectum b) Anus c) Large intestine d) Small intestine
Which enzyme breaks down proteins in the stomach? a) Amylase b) Pepsin c) Lipase d) Trypsin
The gallbladder stores: a) Pancreatic juice b) Gastric juice c) Bile d) Saliva
Mechanical digestion in the mouth involves: a) Enzyme action b) Acid secretion c) Chewing d) Peristalsis
The pharynx serves as a passageway between: a) Stomach and small intestine b) Mouth and esophagus c) Small and large intestine d) Esophagus and stomach
Pancreatic amylase acts on: a) Proteins b) Fats c) Carbohydrates d) Vitamins
The enzyme maltase breaks down: a) Proteins b) Fats c) Maltose d) Starch
Fatty acids and glycerol are the end products of: a) Protein digestion b) Carbohydrate digestion c) Fat digestion d) Nucleic acid digestion
Trypsin is a: a) Carbohydrase b) Protease c) Lipase d) Amylase
The opening through which feces are expelled is: a) Rectum b) Anus c) Large intestine d) Small intestine
Sucrase enzyme breaks down: a) Starch b) Sucrose c) Lactose d) Maltose
The stomach churns food to form: a) Bolus b) Chyme c) Feces d) Bile
Which of the following is NOT a function of the mouth? a) Ingestion b) Mechanical digestion c) Chemical digestion d) Absorption
Pancreatic lipase requires which substance for optimal function? a) HCl b) Bile c) Pepsin d) Amylase
The small intestine receives digestive juices from: a) Liver only b) Pancreas only c) Both liver and pancreas d) Stomach only
Lactase enzyme is responsible for digesting: a) Milk proteins b) Milk sugar c) Milk fats d) Milk vitamins
The esophagus is also known as: a) Wind pipe b) Food pipe c) Bile duct d) Pancreatic duct
Protein digestion begins in the: a) Mouth b) Stomach c) Small intestine d) Large intestine
The end products of protein digestion are: a) Fatty acids b) Glucose c) Amino acids d) Glycerol
Bile helps in: a) Protein digestion b) Carbohydrate digestion c) Fat emulsification d) Water absorption
The muscular contractions in the esophagus move food: a) Upward b) Downward c) Sideways d) In circles
Which organ stores and concentrates bile? a) Liver b) Pancreas c) Gallbladder d) Stomach
Hydrochloric acid in the stomach: a) Activates pepsin only b) Kills bacteria only c) Both activates pepsin and kills bacteria d) Neutralizes food
The breakdown of large fat globules into smaller ones is called: a) Digestion b) Absorption c) Emulsification d) Secretion
Intestinal peptidases act on: a) Proteins b) Polypeptides c) Amino acids d) Carbohydrates
The primary function of the rectum is: a) Digestion b) Absorption c) Storage of feces d) Secretion
Salivary amylase works optimally in: a) Acidic medium b) Basic medium c) Neutral medium d) Any medium
The stomach wall secretes: a) Bile b) Pancreatic juice c) Gastric juice d) Intestinal juice
Which enzyme is NOT produced by the pancreas? a) Amylase b) Lipase c) Trypsin d) Pepsin
The final products of carbohydrate digestion include: a) Amino acids b) Fatty acids c) Monosaccharides d) Polypeptides
Food moves from the pharynx to the: a) Stomach b) Esophagus c) Small intestine d) Large intestine
The large intestine is primarily involved in: a) Chemical digestion b) Mechanical digestion c) Water absorption d) Enzyme production
Pepsin functions optimally in: a) Acidic conditions b) Basic conditions c) Neutral conditions d) Any conditions
The pancreas produces: a) Only enzymes b) Only hormones c) Both enzymes and hormones d) Only bile
Starch digestion begins in the: a) Stomach b) Mouth c) Small intestine d) Large intestine
The enzyme responsible for fat digestion is: a) Amylase b) Pepsin c) Lipase d) Maltase
Gastric juice is produced by: a) Liver b) Pancreas c) Stomach d) Small intestine
The absorption of nutrients primarily occurs in: a) Stomach b) Small intestine c) Large intestine d) Mouth
Which of the following is a monosaccharide? a) Starch b) Sucrose c) Glucose d) Lactose
The anus is controlled by: a) Voluntary muscles only b) Involuntary muscles only c) Both voluntary and involuntary muscles d) No muscles
Carbohydrate digestion is completed in the: a) Mouth b) Stomach c) Small intestine d) Large intestine
The liver produces approximately how much bile per day? a) 100-200 ml b) 500-1000 ml c) 1500-2000 ml d) 2500-3000 ml
Which digestive enzyme has the highest pH optimum? a) Pepsin b) Pancreatic amylase c) Salivary amylase d) Lipase
The villi are found in: a) Stomach b) Small intestine c) Large intestine d) Esophagus
Intrinsic factor is produced by: a) Pancreas b) Liver c) Stomach d) Small intestine
The hormone gastrin is produced in: a) Pancreas b) Liver c) Stomach d) Small intestine
Cellulose cannot be digested by humans because: a) It's too hard b) We lack cellulase enzyme c) It's toxic d) It dissolves too quickly
The brush border is found in: a) Stomach b) Small intestine c) Large intestine d) Esophagus
Vitamin B12 absorption requires: a) Bile salts b) Intrinsic factor c) Pepsin d) Amylase
The cecum is part of: a) Small intestine b) Large intestine c) Stomach d) Pancreas
Lactose intolerance is due to deficiency of: a) Amylase b) Lipase c) Lactase d) Pepsin
The appendix is attached to: a) Stomach b) Small intestine c) Cecum d) Rectum
Gastroesophageal reflux is caused by: a) Too much acid production b) Failure of lower esophageal sphincter c) Bacterial infection d) Enzyme deficiency
The pyloric sphincter controls movement between: a) Esophagus and stomach b) Stomach and small intestine c) Small and large intestine d) Rectum and anus
Zymogen granules contain: a) Active enzymes b) Inactive enzyme precursors c) Hormones d) Vitamins
The enterokinase enzyme is produced by: a) Pancreas b) Liver c) Small intestine d) Stomach
Cholecystokinin (CCK) stimulates: a) Gastric acid secretion b) Pancreatic enzyme secretion c) Salivary secretion d) Bile production
The ileocecal valve prevents: a) Forward movement of food b) Backward movement of contents c) Acid reflux d) Enzyme inactivation
Pepsinogen is converted to pepsin by: a) Bile b) HCl c) Trypsin d) Amylase
The migrating motor complex occurs during: a) Feeding b) Fasting c) Sleeping d) Exercise
Gastric lipase is most active in: a) Alkaline medium b) Neutral medium c) Acidic medium d) Any medium
The hepatopancreatic ampulla is also called: a) Ampulla of Vater b) Sphincter of Oddi c) Pyloric antrum d) Cardiac sphincter
Secretin hormone stimulates: a) Gastric acid secretion b) Pancreatic bicarbonate secretion c) Bile production d) Salivary secretion
The parietal cells secrete: a) Pepsinogen b) HCl and intrinsic factor c) Mucus d) Gastrin
Trypsinogen is activated by: a) HCl b) Pepsin c) Enterokinase d) Bile
The chief cells secrete: a) HCl b) Pepsinogen c) Mucus d) Gastrin
Micelles are formed by: a) Proteins b) Carbohydrates c) Bile salts and lipids d) Vitamins
The haustra are found in: a) Small intestine b) Large intestine c) Stomach d) Esophagus
Vitamin K is produced by bacteria in: a) Stomach b) Small intestine c) Large intestine d) Mouth
The gastrocolic reflex stimulates: a) Gastric emptying b) Colonic motility c) Pancreatic secretion d) Bile release
Chylomicrons transport: a) Proteins b) Carbohydrates c) Lipids d) Vitamins
The myenteric plexus controls: a) Secretion b) Motility c) Absorption d) Blood flow
Gastric inhibitory peptide (GIP) is released by: a) Stomach b) Pancreas c) Small intestine d) Large intestine
The muscularis externa has how many layers? a) One b) Two c) Three d) Four
Brunner's glands are found in: a) Stomach b) Duodenum c) Jejunum d) Ileum
The hormone motilin stimulates: a) Gastric acid secretion b) Intestinal motility c) Pancreatic secretion d) Bile release
Peyer's patches are found in: a) Stomach b) Small intestine c) Large intestine d) Pancreas
The anal sphincters are: a) Both voluntary b) Both involuntary c) Internal involuntary, external voluntary d) Internal voluntary, external involuntary
Segmentation movements help in: a) Propulsion only b) Mixing only c) Both mixing and propulsion d) Neither mixing nor propulsion
The mesentery supports: a) Stomach b) Small intestine c) Large intestine d) Liver
Crypts of Lieberkühn are found in: a) Stomach b) Small intestine c) Large intestine d) Pancreas
The vagus nerve stimulates: a) Gastric secretion b) Pancreatic secretion c) Bile release d) All of the above
Cholesterol is converted to bile acids in: a) Pancreas b) Liver c) Gallbladder d) Small intestine
The enterohepatic circulation involves: a) Proteins b) Carbohydrates c) Bile salts d) Vitamins
Pancreatic polypeptide is secreted by: a) Alpha cells b) Beta cells c) Delta cells d) PP cells
The cephalic phase of gastric secretion is mediated by: a) Hormones b) Neural pathways c) Local reflexes d) Mechanical stimuli
Zollinger-Ellison syndrome involves excessive secretion of: a) Insulin b) Gastrin c) Secretin d) CCK
The gastric phase of digestion is triggered by: a) Sight of food b) Smell of food c) Food entering stomach d) Food entering small intestine
Pancreatic juice contains: a) Only enzymes b) Only bicarbonate c) Both enzymes and bicarbonate d) Only water
The intestinal phase of gastric secretion: a) Stimulates gastric secretion b) Inhibits gastric secretion c) Has no effect d) Varies with food type
The most important factor for fat absorption is: a) Pancreatic lipase b) Bile salts c) Gastric lipase d) Intestinal motility

Section B: Short Answer Questions (1 Mark each) - 100 Questions

Instructions: Write brief answers in one or two sentences.

Name the enzyme present in saliva and its function.
What is peristalsis?
Define chyme.
What activates pepsinogen to pepsin?
Name two functions of bile.
Where does protein digestion begin?
What are the end products of carbohydrate digestion?
Which organ produces pancreatic juice?
What is the function of the rectum?
Name the opening through which food enters the digestive system.
What is mechanical digestion?
Where is bile stored?
What is the function of hydrochloric acid in the stomach?
Name the enzyme that digests fats.
What connects the mouth to the esophagus?
Define emulsification.
Where does the absorption of nutrients primarily occur?
What are the products of protein digestion?
Name the semi-liquid mass formed in the stomach.
What is the function of the large intestine?
Which enzyme breaks down starch in the mouth?
What is the alternative name for the esophagus?
Name the hormone that stimulates gastric acid secretion.
What are villi?
Define bolus.
Which cells produce hydrochloric acid in the stomach?
What is the function of the pyloric sphincter?
Name the enzyme that converts trypsinogen to trypsin.
What is the brush border?
Where are Peyer's patches located?
What is the function of the cardiac sphincter?
Name the hormone produced by S cells.
What are haustra?
Define zymogen.
What is the function of the ileocecal valve?
Name the plexus that controls intestinal motility.
What are chylomicrons?
Where is intrinsic factor produced?
What is the function of the anal sphincter?
Define segmentation.
What are micelles?
Name the cells that secrete pepsinogen.
What is the gastrocolic reflex?
Where are Brunner's glands located?
What is the function of the mesentery?
Name the valve between the small and large intestine.
What are crypts of Lieberkühn?
Define the cephalic phase of digestion.
What is the function of cholecystokinin?
Where does the digestion of fats begin?
What is the appendix?
Name the enzyme that activates pepsinogen.
What are the functions of pancreatic juice?
Define the hepatopancreatic ampulla.
What is the role of the vagus nerve in digestion?
Name the hormone that inhibits gastric secretion.
What are the components of gastric juice?
Define the enterohepatic circulation.
What is the function of motilin?
Where are the taste buds located?
What is gastroesophageal reflux?
Name the enzyme that digests proteins in the small intestine.
What is the function of the gallbladder?
Define the intestinal phase of digestion.
What are the layers of the digestive tract wall?
Name the hormone that stimulates pancreatic enzyme secretion.
What is the function of the cecum?
Define peristaltic waves.
What is the role of bacteria in the large intestine?
Name the sphincter that controls the release of bile.
What is the function of the duodenum?
Define the migrating motor complex.
What are the products of fat digestion?
Name the hormone that regulates blood sugar.
What is the function of the jejunum?
Define gastric emptying.
What is the role of the ileum?
Name the enzyme that breaks down lactose.
What is the function of the colon?
Define the defecation reflex.
What are the components of pancreatic juice?
Name the cells that produce gastrin.
What is the function of the sigmoid colon?
Define malabsorption.
What is the role of the rectum in defecation?
Name the enzyme that digests sucrose.
What is the function of the transverse colon?
Define the gastric phase of digestion.
What is the role of the ascending colon?
Name the hormone that stimulates bile release.
What is the function of the descending colon?
Define steatorrhea.
What is the role of the anal canal?
Name the enzyme that digests maltose.
What is the function of the hepatic flexure?
Define achlorhydria.
What is the role of the splenic flexure?
Name the hormone produced by K cells.
What is the function of the taeniae coli?
Define dumping syndrome.

Section C: Short Answer Questions (2 Marks each) - 25 Questions

Instructions: Write detailed answers in 3-4 sentences.

Explain the process of carbohydrate digestion from mouth to small intestine.
Describe the structure and function of the stomach in digestion.
How does the pancreas contribute to digestion? Mention its secretions.
Explain the role of bile in fat digestion and where it is produced and stored.
Describe the process of protein digestion in the stomach and small intestine.
What are the functions of the small intestine in digestion and absorption?
Explain the mechanism of peristalsis in the esophagus.
Describe the structure and function of villi in nutrient absorption.
How does the large intestine contribute to the digestive process?
Explain the neural and hormonal control of gastric secretion.
Describe the process of fat emulsification and its importance.
What are the different phases of swallowing and their mechanisms?
Explain the role of digestive enzymes in breaking down food molecules.
Describe the structure and function of the liver in digestion.
How do the digestive hormones regulate the digestive process?
Explain the absorption of different nutrients in the small intestine.
Describe the defecation reflex and its control mechanisms.
What are the protective mechanisms of the stomach against acid damage?
Explain the enterohepatic circulation of bile salts.
Describe the motility patterns in the small intestine.
How does the digestive system adapt to different types of food?
Explain the role of the microbiome in the large intestine.
Describe the coordination between the digestive and nervous systems.
What are the common digestive disorders and their causes?
Explain the regulation of pancreatic secretions.

Section D: Long Answer Questions (3 Marks each) - 25 Questions

Instructions: Write comprehensive answers with proper explanations, examples, and diagrams where necessary.

Describe in detail the complete journey of food through the digestive system, highlighting the major processes occurring at each stage.
Explain the comprehensive process of protein digestion, including all enzymes involved, their sources, activation mechanisms, and end products.
Discuss the structure and functions of the liver in detail, emphasizing its role in digestion, metabolism, and detoxification.
Describe the hormonal regulation of digestion, including the major digestive hormones, their sources, targets, and functions.
Explain the detailed mechanism of fat digestion and absorption, including the role of bile, pancreatic lipase, and the formation of micelles and chylomicrons.
Discuss the structure and function of the pancreas, including both its exocrine and endocrine functions in relation to digestion.
Describe the detailed anatomy and physiology of the small intestine, emphasizing its adaptations for maximum absorption.
Explain the neural control of digestion, including the role of the enteric nervous system, vagus nerve, and various reflexes.
Discuss the process of carbohydrate digestion in detail, from complex polysaccharides to monosaccharide absorption.
Describe the structure and function of the stomach, including gastric secretions, their regulation, and protective mechanisms.
Explain the process of defecation, including the anatomy involved, neural control, and the defecation reflex.
Discuss the role of the large intestine in digestion, including water absorption, electrolyte balance, and the gut microbiome.
Describe the pathophysiology of common digestive disorders such as peptic ulcers, gastroesophageal reflux disease, and inflammatory bowel disease.
Explain the coordination between digestion and metabolism, including how digestive products enter metabolic pathways.
Discuss the adaptations of the digestive system to different dietary requirements and nutritional states.
Describe the development and regeneration of the digestive system, including stem cell populations and tissue renewal.
Explain the immune functions of the digestive system, including gut-associated lymphoid tissue (GALT) and mucosal immunity.
Discuss the relationship between the digestive system and other body systems, including circulatory, nervous, and endocrine systems.
Describe the molecular mechanisms of nutrient absorption, including transport proteins, carrier systems, and cellular uptake mechanisms.
Explain the regulation of digestive enzyme secretion and activation, including zymogen activation and feedback mechanisms.
Discuss the role of the digestive system in maintaining homeostasis, including pH regulation, fluid balance, and nutrient storage.
Describe the evolutionary adaptations of the human digestive system compared to other mammals and dietary specialists.
Explain the pharmacological aspects of digestion, including how drugs affect digestive processes and drug absorption through the GI tract.
Discuss the diagnostic methods used to assess digestive system function and common laboratory tests for digestive disorders.
Describe the surgical interventions commonly performed on the digestive system and their physiological consequences.

Answer Key

Digestive System Answer Script

Section A: Multiple Choice Questions (MCQs)

b) Breaking down food into smaller molecules
c) Amylase
a) Peristalsis
c) Hydrochloric acid and pepsin
b) Chyme
c) Small intestine
b) Liver
c) Hydrochloric acid
c) Water and electrolyte absorption
a) Rectum
b) Pepsin
c) Bile
c) Chewing
b) Mouth and esophagus
c) Carbohydrates
c) Maltose
c) Fat digestion
b) Protease
b) Anus
b) Sucrose
b) Chyme
d) Absorption
b) Bile
c) Both liver and pancreas
b) Milk sugar
b) Food pipe
b) Stomach
c) Amino acids
c) Fat emulsification
b) Downward
c) Gallbladder
c) Both activates pepsin and kills bacteria
c) Emulsification
b) Polypeptides
c) Storage of feces
c) Neutral medium
c) Gastric juice
d) Pepsin
c) Monosaccharides
b) Esophagus
c) Water absorption
a) Acidic conditions
c) Both enzymes and hormones
b) Mouth
c) Lipase
c) Stomach
b) Small intestine
c) Glucose
c) Both voluntary and involuntary muscles
c) Small intestine
b) 500-1000 ml
b) Pancreatic amylase
b) Small intestine
c) Stomach
c) Stomach
b) We lack cellulase enzyme
b) Small intestine
b) Intrinsic factor
b) Large intestine
c) Lactase
c) Cecum
b) Failure of lower esophageal sphincter
b) Stomach and small intestine
b) Inactive enzyme precursors
c) Small intestine
b) Pancreatic enzyme secretion
b) Backward movement of contents
b) HCl
b) Fasting
c) Acidic medium
a) Ampulla of Vater
b) Pancreatic bicarbonate secretion
b) HCl and intrinsic factor
c) Enterokinase
b) Pepsinogen
c) Bile salts and lipids
b) Large intestine
c) Large intestine
b) Colonic motility
c) Lipids
b) Motility
c) Small intestine
b) Two
b) Duodenum
b) Intestinal motility
b) Small intestine
c) Internal involuntary, external voluntary
c) Both mixing and propulsion
b) Small intestine
b) Small intestine
d) All of the above
b) Liver
c) Bile salts
d) PP cells
b) Neural pathways
b) Gastrin
c) Food entering stomach
c) Both enzymes and bicarbonate
b) Inhibits gastric secretion
b) Bile salts

Section B: Short Answer Questions (1 Mark each)

Enzyme in saliva: Salivary amylase; begins carbohydrate digestion.
Peristalsis: Wave-like muscle contractions that move food through the digestive tract.
Chyme: A semi-liquid paste of partially digested food and stomach juices.
Pepsinogen activation: Hydrochloric acid (HCl) activates pepsinogen into pepsin.
Bile functions: Emulsifies fats and aids in the absorption of fat-soluble vitamins.
Protein digestion start: Protein digestion begins in the stomach.
Carbohydrate digestion end products: Monosaccharides (e.g., glucose, fructose, galactose).
Pancreatic juice production: The pancreas.
Rectum function: Stores feces before defecation.
Food entry opening: The mouth.
Mechanical digestion: The physical breakdown of food into smaller pieces (e.g., chewing).
Bile storage: The gallbladder.
HCl function: Kills pathogens and activates pepsin.
Fat-digesting enzyme: Lipase.
Mouth to esophagus connection: The pharynx.
Emulsification: The breakdown of large fat globules into smaller droplets.
Nutrient absorption site: The small intestine.
Protein digestion products: Amino acids.
Stomach's semi-liquid mass: Chyme.
Large intestine function: Absorbs water and electrolytes, and forms feces.
Starch-breaking enzyme in mouth: Salivary amylase.
Esophagus alternative name: Food pipe.
Gastric acid stimulating hormone: Gastrin.
Villi: Finger-like projections in the small intestine that increase surface area for absorption.
Bolus: A chewed, soft mass of food mixed with saliva.
HCl producing cells: Parietal cells.
Pyloric sphincter function: Controls the passage of chyme from the stomach to the small intestine.
Trypsinogen to trypsin enzyme: Enterokinase.
Brush border: Microvilli on the surface of intestinal cells that increase surface area.
Peyer's patches location: The ileum of the small intestine.
Cardiac sphincter function: Prevents stomach contents from refluxing into the esophagus.
S cell hormone: Secretin.
Haustra: Pouches in the wall of the large intestine.
Zymogen: An inactive precursor of an enzyme.
Ileocecal valve function: Prevents backflow from the large intestine into the small intestine.
Intestinal motility plexus: Myenteric plexus.
Chylomicrons: Lipoprotein particles that transport dietary lipids from the intestines.
Intrinsic factor production: Parietal cells in the stomach.
Anal sphincter function: Controls the expulsion of feces.
Segmentation: Mixing contractions in the small intestine.
Micelles: Tiny spherical complexes of emulsified fat that arise during digestion.
Pepsinogen secreting cells: Chief cells.
Gastrocolic reflex: A reflex that increases motility in the colon in response to food in the stomach.
Brunner's glands location: The duodenum.
Mesentery function: Supports and suspends the small intestine from the abdominal wall.
Small to large intestine valve: Ileocecal valve.
Crypts of Lieberkühn: Glands found in the intestinal lining that secrete intestinal juice.
Cephalic phase: The initial phase of digestion, stimulated by the sight, smell, or thought of food.
Cholecystokinin (CCK) function: Stimulates pancreatic enzyme secretion and gallbladder contraction.
Fat digestion start: The small intestine.
Appendix: A small, finger-like tube attached to the cecum.
Pepsinogen activating enzyme: Pepsin (autocatalysis) and HCl.
Pancreatic juice functions: Neutralizes stomach acid and provides enzymes for digestion.
Hepatopancreatic ampulla: The duct formed by the union of the pancreatic duct and the common bile duct.
Vagus nerve role: Stimulates gastric secretion and motility.
Gastric secretion inhibiting hormone: Somatostatin and Secretin.
Gastric juice components: Hydrochloric acid, pepsin, mucus, and intrinsic factor.
Enterohepatic circulation: The circulation of bile salts from the liver to the intestine and back to the liver.
Motilin function: Stimulates migrating motor complexes in the gut.
Taste buds location: Primarily on the tongue.
Gastroesophageal reflux: The backflow of stomach contents into the esophagus.
Protein-digesting enzyme in small intestine: Trypsin and chymotrypsin.
Gallbladder function: Stores and concentrates bile.
Intestinal phase: The phase of digestion stimulated by the entry of chyme into the small intestine.
Digestive tract wall layers: Mucosa, submucosa, muscularis externa, and serosa.
Pancreatic enzyme stimulating hormone: Cholecystokinin (CCK).
Cecum function: A pouch connected to the junction of the ileum and the colon that absorbs fluids and salts.
Peristaltic waves: Coordinated muscular contractions that propel food forward.
Bacteria role in large intestine: Synthesize vitamins (like Vitamin K) and ferment undigested carbohydrates.
Bile release sphincter: Sphincter of Oddi.
Duodenum function: The first part of the small intestine where most chemical digestion occurs.
Migrating motor complex: A pattern of electromechanical activity observed in GI smooth muscle during fasting.
Fat digestion products: Fatty acids and glycerol.
Blood sugar regulating hormone: Insulin and glucagon.
Jejunum function: The middle part of the small intestine responsible for the absorption of nutrients.
Gastric emptying: The process by which food leaves the stomach and enters the small intestine.
Ileum role: The final section of the small intestine, responsible for absorbing vitamin B12 and bile salts.
Lactose-breaking enzyme: Lactase.
Colon function: Absorbs water and electrolytes from food matter and passes useless waste from the body.
Defecation reflex: The involuntary response of the lower bowel to stretching of the rectal wall.
Pancreatic juice components: Bicarbonate and digestive enzymes (amylase, lipase, proteases).
Gastrin producing cells: G cells in the stomach.
Sigmoid colon function: Stores fecal matter before it moves into the rectum.
Malabsorption: Impaired absorption of nutrients from the intestines.
Rectum's role in defecation: Stores feces and triggers the defecation reflex when stretched.
Sucrose-digesting enzyme: Sucrase.
Transverse colon function: Absorbs water and salts.
Gastric phase: The phase of digestion stimulated by the presence of food in the stomach.
Ascending colon role: Absorbs remaining water and other key nutrients from indigestible material.
Bile release stimulating hormone: Cholecystokinin (CCK).
Descending colon function: Stores feces that will eventually be emptied into the rectum.
Steatorrhea: The presence of excess fat in feces.
Anal canal role: The terminal part of the large intestine, which terminates at the anus.
Maltose-digesting enzyme: Maltase.
Hepatic flexure function: The bend in the colon between the ascending and transverse colon.
Achlorhydria: The absence of hydrochloric acid in gastric secretions.
Splenic flexure role: The bend in the colon between the transverse and descending colon.
K cell hormone: Gastric inhibitory peptide (GIP).
Taeniae coli function: Three separate longitudinal ribbons of smooth muscle on the outside of the colon that contract to form haustra.
Dumping syndrome: A condition where food moves too quickly from the stomach to the small intestine.

Section C: Short Answer Questions (2 Marks each)

Carbohydrate Digestion: Digestion begins in the mouth where salivary amylase breaks down starch. It ceases in the stomach's acid and resumes in the small intestine. Here, pancreatic amylase continues breaking down starch, and brush border enzymes (maltase, sucrase, lactase) break disaccharides into monosaccharides for absorption.
Stomach Structure and Function: The stomach is a muscular organ that stores food, initiating protein digestion. Its walls secrete gastric juice containing hydrochloric acid, which kills bacteria and activates pepsin. The stomach's churning action mixes food with these juices to form chyme.
Pancreas Contribution: The pancreas secretes pancreatic juice into the small intestine. This juice contains bicarbonate to neutralize stomach acid and a variety of enzymes, including amylase for carbohydrates, lipase for fats, and proteases (like trypsin) for proteins.
Bile's Role: Bile is produced by the liver and stored in the gallbladder. It is released into the small intestine to emulsify fats, breaking large globules into smaller droplets. This increases the surface area for pancreatic lipase to act upon, aiding fat digestion.
Protein Digestion: Protein digestion starts in the stomach, where pepsin breaks proteins into smaller polypeptides. In the small intestine, pancreatic proteases like trypsin and chymotrypsin further break down polypeptides. Finally, peptidases on the intestinal wall break them into amino acids for absorption.
Small Intestine Functions: The small intestine is the primary site for the chemical digestion of carbohydrates, proteins, and fats, using enzymes from the pancreas and its own wall. It is also the main site for the absorption of most nutrients, water, vitamins, and minerals into the bloodstream.
Peristalsis in Esophagus: Peristalsis is a series of wave-like muscle contractions that move food through the esophagus. Circular muscles contract behind the bolus to prevent it from moving backward, while longitudinal muscles ahead of the bolus contract to shorten the passageway, pushing it forward.
Villi Structure and Function: Villi are small, finger-like projections lining the small intestine. They vastly increase the surface area available for nutrient absorption. Each villus contains a network of capillaries and a lacteal, which absorb digested nutrients into the blood and lymph respectively.
Large Intestine Contribution: The large intestine primarily absorbs water and electrolytes from the remaining indigestible food matter. It also compacts and stores this material as feces before it is eliminated from the body. Gut bacteria within it also synthesize certain vitamins.
Control of Gastric Secretion: Gastric secretion is controlled by both nerves and hormones. The vagus nerve (neural control) stimulates secretion in response to the sight or smell of food. The hormone gastrin (hormonal control) is released when food enters the stomach, further stimulating acid production.
Fat Emulsification: Emulsification is the process where bile salts break down large fat globules in the chyme into much smaller fat droplets. This is crucial because it increases the surface area of the fat, allowing the water-soluble enzyme pancreatic lipase to access and digest the fat molecules effectively.
Phases of Swallowing: Swallowing (deglutition) has three phases. The voluntary buccal phase involves pushing the bolus to the back of the mouth. The involuntary pharyngeal phase involves the soft palate rising and the epiglottis closing the airway. The final esophageal phase involves peristalsis moving the bolus down to the stomach.
Role of Digestive Enzymes: Digestive enzymes are biological catalysts that speed up the breakdown of complex food molecules into simpler, absorbable units. For example, amylases break down carbohydrates, proteases break down proteins, and lipases break down fats, making them small enough to be absorbed by the intestines.
Liver's Role in Digestion: The liver's main digestive function is the production of bile, which is essential for fat digestion and absorption. Beyond digestion, the liver also plays a vital role in metabolizing absorbed nutrients, detoxifying harmful substances, and synthesizing essential proteins.
Hormonal Regulation: Digestive hormones like gastrin, secretin, and cholecystokinin (CCK) regulate digestion. Gastrin stimulates stomach acid production. Secretin stimulates the pancreas to release bicarbonate. CCK stimulates pancreatic enzyme release and gallbladder contraction, coordinating the digestive process.
Nutrient Absorption: In the small intestine, carbohydrates (as monosaccharides) and proteins (as amino acids) are absorbed into the blood capillaries. Fats (as fatty acids and glycerol) are absorbed into lacteals, forming chylomicrons. Water, vitamins, and minerals are also absorbed along the length of the intestine.
Defecation Reflex: When feces enter and stretch the rectum, stretch receptors trigger a spinal reflex, causing the internal anal sphincter to relax. Defecation is consciously controlled by the voluntary relaxation or constriction of the external anal sphincter, allowing for the elimination of feces.
Stomach's Protective Mechanisms: The stomach is protected from its own acidic environment by a thick layer of bicarbonate-rich mucus that coats the stomach lining. Additionally, the epithelial cells of the stomach have tight junctions to prevent acid from leaking, and they regenerate rapidly.
Enterohepatic Circulation of Bile: This is the recycling of bile salts. After aiding in fat digestion and absorption in the small intestine, most bile salts are reabsorbed in the ileum and returned to the liver via the portal vein. The liver then re-secretes them into the bile, conserving the body's supply.
Small Intestine Motility: The small intestine exhibits two main motility patterns. Segmentation consists of localized mixing contractions that churn the chyme with digestive juices and facilitate contact with the mucosa for absorption. Peristalsis consists of propulsive contractions that move the contents slowly along the intestine.
Digestive System Adaptation: The digestive system adapts to diet by adjusting enzyme secretion. For instance, a high-carbohydrate meal can lead to an increase in amylase production. Similarly, the composition of gut microbiota can change over time based on long-term dietary patterns, affecting how certain foods are processed.
Large Intestine Microbiome: The large intestine hosts a vast community of bacteria (the gut microbiome). These microbes help ferment undigested carbohydrates, produce essential vitamins like vitamin K and some B vitamins, and play a crucial role in training the immune system and preventing the growth of harmful bacteria.
Digestive and Nervous System Coordination: The nervous system, particularly the enteric nervous system (the "brain of the gut") and the autonomic nervous system (via the vagus nerve), controls digestive processes. It regulates motility (peristalsis, segmentation) and secretions from glands in response to stimuli like food presence.
Common Digestive Disorders: Common disorders include Gastroesophageal Reflux Disease (GERD), caused by a weak lower esophageal sphincter allowing acid reflux. Peptic ulcers are sores in the stomach or duodenum lining, often caused by H. pylori bacteria or NSAID use. Inflammatory Bowel Disease (IBD) is chronic inflammation of the digestive tract.
Regulation of Pancreatic Secretions: Pancreatic secretion is regulated by hormones. Secretin, released in response to acidic chyme in the duodenum, stimulates the pancreas to release bicarbonate-rich fluid to neutralize the acid. Cholecystokinin (CCK), released in response to fats and proteins, stimulates the secretion of digestive enzymes.

Section D: Long Answer Questions (3 Marks each)

Journey of Food: Food begins its journey in the mouth, where chewing (mechanical digestion) and salivary amylase (chemical digestion of carbs) create a bolus. The bolus is swallowed, passing through the pharynx and esophagus via peristalsis. In the stomach, food is mixed with gastric juice (HCl and pepsin), beginning protein digestion and forming chyme. The chyme is slowly released into the small intestine, the primary site for digestion and absorption. Here, bile from the liver and enzymes from the pancreas break down fats, proteins, and carbohydrates, and the resulting nutrients are absorbed through the intestinal walls. The remaining indigestible material moves to the large intestine, where water is absorbed and feces are formed. Finally, feces are stored in the rectum and eliminated through the anus.
Protein Digestion: The digestion of protein begins in the stomach. The acidic environment (due to HCl) denatures proteins and activates pepsinogen into its active form, pepsin. Pepsin breaks down large protein molecules into smaller polypeptides. When the chyme enters the small intestine, the pancreas releases inactive proteases (zymogens) like trypsinogen. The intestinal enzyme enterokinase activates trypsinogen to trypsin. Trypsin then activates other pancreatic proteases, such as chymotrypsin, and also continues to break down polypeptides. Finally, peptidases on the brush border of the intestinal cells break down the remaining small polypeptides into single amino acids, which are then absorbed into the bloodstream.
Liver Structure and Functions: The liver, the largest internal organ, is located in the upper right quadrant of the abdomen. Its digestive function is to produce bile, an alkaline fluid containing bile salts, which emulsifies fats in the small intestine, aiding their digestion. Beyond digestion, the liver has critical metabolic functions: it processes absorbed nutrients, stores glucose as glycogen, synthesizes plasma proteins, and metabolizes fats and proteins. It also serves as a primary site for detoxification, breaking down harmful substances like alcohol and drugs, and converting toxic ammonia into urea for excretion.
Hormonal Regulation of Digestion: Digestion is regulated by several key hormones. Gastrin, produced by the stomach, is released in response to food presence and stimulates the secretion of gastric acid. When acidic chyme enters the duodenum, the small intestine releases secretin, which stimulates the pancreas to secrete bicarbonate to neutralize the acid. The presence of fats and proteins in the duodenum triggers the release of cholecystokinin (CCK), which stimulates the pancreas to release digestive enzymes and the gallbladder to contract and release bile. These hormones work in a coordinated fashion to ensure enzymes and bile are present when needed.
Fat Digestion and Absorption: Fat digestion occurs almost entirely in the small intestine. First, large fat globules are emulsified by bile salts (from the liver) into smaller droplets, increasing the surface area for enzymes. Pancreatic lipase, an enzyme from the pancreas, then breaks down these fat droplets into fatty acids and glycerol. These products, along with bile salts, form tiny spherical structures called micelles, which transport the fats to the surface of the intestinal cells. The fatty acids and glycerol diffuse into the cells, where they are reassembled into triglycerides and packaged into larger particles called chylomicrons. These chylomicrons are then absorbed into the lymphatic system via lacteals before entering the bloodstream.
Pancreas Structure and Function: The pancreas is a gland located behind the stomach that has both exocrine and endocrine functions. Its exocrine function is crucial for digestion; it produces pancreatic juice, which contains a mixture of digestive enzymes (amylase, lipase, proteases) and bicarbonate. This juice is secreted into the small intestine to neutralize stomach acid and digest all major food types. Its endocrine function involves the islets of Langerhans, which secrete hormones directly into the bloodstream. These include insulin and glucagon, which are essential for regulating blood glucose levels.
Small Intestine Anatomy and Physiology: The small intestine is a long, coiled tube divided into the duodenum, jejunum, and ileum. Its primary function is nutrient absorption, and its structure is highly adapted for this purpose. The inner wall is folded into circular folds (plicae circulares), which are covered in finger-like projections called villi. The cells on the surface of the villi have even smaller projections called microvilli (forming the brush border). These three levels of folding increase the surface area for absorption by over 600 times, ensuring efficient uptake of nutrients into the blood and lymph.
Neural Control of Digestion: The digestive system is controlled by the enteric nervous system (ENS), often called the "second brain," which can operate independently to control local reflexes for motility and secretion. The ENS is also influenced by the autonomic nervous system. The parasympathetic nervous system (primarily via the vagus nerve) generally stimulates digestion ("rest and digest"), increasing secretion and motility. The sympathetic nervous system ("fight or flight") inhibits digestion. Reflexes like the gastrocolic reflex (food in the stomach stimulates colonic motility) are mediated by this neural network.
Carbohydrate Digestion: The digestion of complex carbohydrates (starch) begins in the mouth with the enzyme salivary amylase. This action stops in the acidic environment of the stomach. In the small intestine, pancreatic amylase continues to break down starch and glycogen into smaller oligosaccharides and disaccharides. The final stage of digestion occurs at the brush border of the small intestine, where enzymes like maltase, sucrase, and lactase break down disaccharides (maltose, sucrose, lactose) into their constituent monosaccharides (glucose, fructose, galactose). These simple sugars are then absorbed across the intestinal wall into the bloodstream.
Stomach Structure and Function: The stomach is a J-shaped muscular organ with four main regions. It acts as a temporary storage tank for food and is a major site for mechanical and chemical digestion. Its muscular walls perform powerful churning motions to mix food with gastric juice. This juice, secreted by gastric glands, contains hydrochloric acid (HCl) to kill microbes and activate enzymes, and pepsinogen, which is converted to pepsin to begin protein digestion. To protect itself from the harsh acidic environment, the stomach lining is coated with a thick, bicarbonate-rich mucus layer.
Process of Defecation: Defecation is the elimination of feces from the body. The process is initiated by the defecation reflex, which occurs when mass movements in the colon push feces into the normally empty rectum, stretching its walls. This stretching triggers a parasympathetic spinal reflex, causing the sigmoid colon and rectum to contract and the internal anal sphincter (involuntary muscle) to relax. The brain also receives a signal, giving the conscious awareness of the need to defecate. The external anal sphincter is under voluntary control, allowing defecation to be postponed until an appropriate time.
Large Intestine and Gut Microbiome: The large intestine's primary roles are to absorb water and electrolytes from indigestible food matter and to form and store feces. It does not produce digestive enzymes. It is also home to the gut microbiome, a complex community of trillions of bacteria. These bacteria play a symbiotic role by fermenting undigested carbohydrates, producing important nutrients like vitamin K and certain B vitamins, and preventing the growth of pathogenic microbes.
Pathophysiology of Digestive Disorders:
- Peptic Ulcers: Open sores on the lining of the stomach or duodenum, primarily caused by the bacterium H. pylori or chronic use of NSAIDs, which erode the protective mucus layer.
- Gastroesophageal Reflux Disease (GERD): A chronic condition where stomach acid frequently flows back into the esophagus due to a weakened lower esophageal sphincter, causing heartburn and irritation.
- Inflammatory Bowel Disease (IBD): A term for two conditions (Crohn's disease and ulcerative colitis) characterized by chronic inflammation of the gastrointestinal tract, leading to symptoms like pain, diarrhea, and weight loss.
Digestion and Metabolism Coordination: The digestive system breaks down food into absorbable nutrients, which are then used in metabolic pathways. For example, glucose absorbed from carbohydrate digestion enters the bloodstream and is used in cellular respiration to produce ATP. Amino acids from protein digestion are used to synthesize new proteins. Fatty acids are used for energy or stored. Hormones like insulin are crucial for this coordination, promoting the uptake and storage of glucose after a meal.
Digestive System Adaptations: The human digestive system is omnivorous, but it can adapt to different diets. For example, the secretion of digestive enzymes can be adjusted based on the macronutrient content of the diet. The composition of the gut microbiome is also highly adaptable and can change significantly based on long-term dietary patterns, influencing how different foods, especially fiber, are processed and the range of nutrients that can be extracted.
Digestive System Development and Regeneration: The digestive tract lining is one of the most rapidly regenerating tissues in the body, with a complete turnover every few days. This is accomplished by intestinal stem cells located at the base of the crypts of Lieberkühn. These stem cells continuously divide to produce new cells that migrate up the villi, differentiating into absorptive cells, goblet cells, and other specialized cell types, ensuring the integrity and function of the intestinal barrier.
Immune Functions of the Digestive System: The digestive system is a major immunological organ. It contains a large amount of Gut-Associated Lymphoid Tissue (GALT), including Peyer's patches in the ileum. This system constantly samples gut contents to distinguish between harmless food antigens, beneficial commensal bacteria, and harmful pathogens. It mounts an immune response against pathogens while maintaining tolerance to non-harmful substances, a critical function for overall health.
Digestive System and Other Body Systems: The digestive system is intricately linked with other systems. The circulatory system transports absorbed nutrients from the gut to the rest of the body. The nervous system (both central and enteric) regulates digestive motility and secretion. The endocrine system coordinates digestion through hormones and is also influenced by it (e.g., gut hormones affecting appetite and insulin release).
Molecular Mechanisms of Nutrient Absorption: Nutrient absorption is a highly specific process. Monosaccharides like glucose are absorbed via secondary active transport with sodium ions (SGLT1) and facilitated diffusion (GLUT2). Amino acids are also absorbed by various active transport mechanisms. Fatty acids and monoglycerides diffuse into intestinal cells, while water is absorbed by osmosis, following the osmotic gradient created by the absorption of solutes.
Regulation of Digestive Enzyme Secretion: Most digestive enzymes are stored and secreted as inactive precursors called zymogens (e.g., pepsinogen, trypsinogen) to prevent them from digesting the cells that produce them. Activation occurs only in the lumen of the GI tract where they are needed. For example, pepsinogen is activated by HCl in the stomach, and trypsinogen is activated by enterokinase in the small intestine. This activation is often a cascade, where one active enzyme activates others, providing a rapid and amplified response.
Digestive System in Homeostasis: The digestive system is vital for maintaining homeostasis. It regulates fluid and electrolyte balance by absorbing water and minerals from the diet. It plays a role in pH regulation through the secretion of bicarbonate by the pancreas to neutralize stomach acid. Most importantly, it provides a constant supply of nutrients to the blood, which is essential for the energy and building blocks required by all body cells to function.
Evolutionary Adaptations: Compared to herbivorous mammals, which have long and complex digestive tracts with fermentation chambers to break down cellulose, the human digestive system is shorter and simpler, reflecting an omnivorous diet. The human gut lacks the enzyme cellulase. However, compared to carnivores, the human small intestine is relatively long, allowing for efficient absorption of nutrients from plant matter.
Pharmacological Aspects of Digestion: Many drugs target the digestive system. For example, proton pump inhibitors (PPIs) reduce the production of stomach acid to treat GERD and ulcers. Laxatives increase gut motility or water content in feces to treat constipation. The GI tract is also a major site for the absorption of most orally administered drugs, and factors like stomach pH and food presence can significantly affect how well a drug is absorbed.
Diagnostic Methods for Digestive System: Digestive function is assessed using various methods. Endoscopy (upper GI) and colonoscopy (lower GI) involve using a flexible camera to visualize the lining of the digestive tract and take biopsies. Barium swallows or enemas use a contrast agent to visualize the GI tract on X-rays. Stool samples can be analyzed for blood, fat, or pathogens, and blood tests can check for liver enzymes or markers of inflammation.
Surgical Interventions on the Digestive System: Common surgical interventions include appendectomy (removal of the appendix), cholecystectomy (removal of the gallbladder), and colectomy (removal of all or part of the colon), often for cancer or IBD. Bariatric surgery (e.g., gastric bypass) alters the stomach and small intestine to induce weight loss. These surgeries can have significant physiological consequences, such as altered nutrient absorption (malabsorption) or changes in bowel habits.

The Digestive System