MCQs on Human Digestive System

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1. Which of the following is the primary function of the small intestine?

  • A) Absorption of water
  • B) Digestion of carbohydrates
  • C) Absorption of nutrients
  • D) Storage of bile

Answer: C) Absorption of nutrients
Explanation: The small intestine is primarily responsible for absorbing nutrients from digested food. It is lined with villi, which increase surface area for absorption of proteins, fats, carbohydrates, vitamins, and minerals into the bloodstream.

2. What is the role of bile in digestion?

  • Neutralizes stomach acid
  • B) Emulsifies fats
  • C) Breaks down proteins
  • D) Stimulates enzyme activity

Answer: B) Emulsifies fats
Explanation: Bile, produced by the liver and stored in the gallbladder, emulsifies fats, breaking them into smaller droplets, which increases the surface area for lipases to digest fat more effectively in the small intestine.

3. Which of the following enzymes breaks down proteins in the stomach?

  • A) Amylase
  • B) Pepsin
  • C) Lipase
  • D) Lactase

Answer: B) Pepsin
Explanation: Pepsin is an enzyme secreted by the stomach lining in its inactive form, pepsinogen. It is activated by stomach acid and plays a crucial role in the breakdown of proteins into peptides during digestion.

4. The absorption of most nutrients takes place in which part of the digestive system?

  • A) Stomach
  • B) Large intestine
  • C) Small intestine
  • D) Mouth

Answer: C) Small intestine
Explanation: The small intestine is the site of nutrient absorption due to its large surface area provided by villi and microvilli. Nutrients like amino acids, fatty acids, glucose, vitamins, and minerals are absorbed into the bloodstream.

5. The enzyme amylase begins the digestion of which macronutrient?

  • A) Proteins
  • B) Fats
  • C) Carbohydrates
  • D) Nucleic acids

Answer: C) Carbohydrates
Explanation: Amylase, found in saliva and pancreatic secretions, begins the breakdown of carbohydrates into simpler sugars, such as maltose, which are further digested in the small intestine by additional enzymes.

6. What is the main function of the large intestine?

  • A) Digest proteins
  • B) Absorb water and electrolytes
  • C) Store bile
  • D) Neutralize stomach acid

Answer: B) Absorb water and electrolytes
Explanation: The large intestine absorbs water, salts, and electrolytes from the remaining indigestible food matter, forming solid feces. It also hosts bacteria that help in the fermentation of undigested materials.

7. Which of the following structures prevents the backflow of stomach contents into the esophagus?

  • A) Pyloric sphincter
  • B) Ileocaecal valve
  • C) Cardiac sphincter
  • D) Anal sphincter

Answer: C) Cardiac sphincter
Explanation: The cardiac sphincter (also known as the lower esophageal sphincter) prevents the backflow (reflux) of stomach acid and contents into the esophagus, protecting the esophageal lining from damage.

8. Which of the following is not a component of pancreatic juice?

  • A) Amylase
  • B) Lipase
  • C) Trypsinogen
  • D) Pepsin

Answer: D) Pepsin
Explanation: Pepsin is an enzyme found in the stomach for protein digestion, while pancreatic juice contains amylase, lipase, and trypsinogen, which aid in the digestion of carbohydrates, fats, and proteins in the small intestine.

9. What is the function of the liver in digestion?

  • A) Secretion of digestive enzymes
  • B) Production of bile
  • C) Storage of vitamins
  • D) Secretion of hydrochloric acid

Answer: B) Production of bile
Explanation: The liver produces bile, which is stored in the gallbladder and released into the small intestine. Bile is essential for the emulsification of fats and assists in the absorption of fat-soluble vitamins.

10. The process of peristalsis is responsible for:

  • A) The breakdown of food by enzymes
  • B) The movement of food along the digestive tract
  • C) The absorption of nutrients
  • D) The production of bile

Answer: B) The movement of food along the digestive tract
Explanation: Peristalsis is a series of wave-like muscle contractions that move food along the digestive tract from the mouth to the anus. This process occurs throughout the esophagus, stomach, and intestines.

11. Which of the following is the primary function of the stomach?

  • A) Absorption of water
  • B) Absorption of nutrients
  • C) Storage and partial digestion of food
  • D) Production of digestive enzymes

Answer: C) Storage and partial digestion of food
Explanation: The stomach temporarily stores food and initiates the breakdown of proteins through the action of stomach acid and enzymes like pepsin. It also churns food into a semi-liquid substance called chyme.

12. What is the role of intrinsic factor in digestion?

  • A) Digests proteins
  • B) Absorbs vitamin B12
  • C) Stimulates bile production
  • D) Produces pancreatic enzymes

Answer: B) Absorbs vitamin B12
Explanation: Intrinsic factor is a glycoprotein secreted by parietal cells in the stomach that is essential for the absorption of vitamin B12 in the ileum, crucial for red blood cell production and neurological function.

13. Which of the following organs produces insulin?

  • A) Liver
  • B) Stomach
  • C) Pancreas
  • D) Gallbladder

Answer: C) Pancreas
Explanation: The pancreas produces insulin in its beta cells located in the islets of Langerhans. Insulin helps regulate blood glucose levels by promoting the uptake of glucose into cells for energy production.

14. The enzyme lipase breaks down:

  • A) Proteins
  • B) Carbohydrates
  • C) Fats
  • D) Nucleic acids

Answer: C) Fats
Explanation: Lipase is an enzyme that breaks down lipids (fats) into fatty acids and glycerol. It is secreted by the pancreas and works in the small intestine, where it aids in the digestion of dietary fats.

15. Which part of the digestive system is responsible for most of the digestion and nutrient absorption?

  • A) Stomach
  • B) Small intestine
  • C) Large intestine
  • D) Esophagus

Answer: B) Small intestine
Explanation: The small intestine is the primary site for both digestion and nutrient absorption. Enzymes from the pancreas and bile from the liver help digest nutrients, which are absorbed through the intestinal wall into the bloodstream.

16. What is the function of the pyloric sphincter?

  • A) Prevents backflow of food into the stomach
  • B) Controls the release of chyme into the small intestine
  • C) Secretes digestive enzymes
  • D) Absorbs nutrients

Answer: B) Controls the release of chyme into the small intestine
Explanation: The pyloric sphincter controls the release of partially digested food (chyme) from the stomach into the duodenum, the first part of the small intestine, where further digestion occurs.

17. Which of the following is a function of the large intestine?

  • A) Absorption of nutrients
  • B) Digestion of proteins
  • C) Synthesis of vitamins by gut bacteria
  • D) Production of bile

Answer: C) Synthesis of vitamins by gut bacteria
Explanation: The large intestine houses a large population of bacteria that synthesize vitamins, such as vitamin K and some B vitamins, which are absorbed into the bloodstream. It also absorbs water and electrolytes.

18. The villi in the small intestine are important for:

  • A) Breaking down food
  • B) Producing digestive enzymes
  • C) Increasing surface area for absorption
  • D) Secreting bile

Answer: C) Increasing surface area for absorption
Explanation: The villi, tiny finger-like projections in the lining of the small intestine, greatly increase its surface area. This allows for more efficient absorption of nutrients into the bloodstream.

19. The pancreas has both exocrine and endocrine functions. Which of the following is an exocrine function?

  • A) Insulin secretion
  • B) Glucagon secretion
  • C) Production of digestive enzymes
  • D) Regulation of blood sugar

Answer: C) Production of digestive enzymes
Explanation: The pancreas functions as an exocrine gland by secreting digestive enzymes (amylase, lipase, and proteases) into the small intestine to help break down food. Its endocrine function involves insulin and glucagon production.

20. Which structure prevents the entry of food into the trachea during swallowing?

  • A) Epiglottis
  • B) Uvula
  • C) Cardiac sphincter
  • D) Ileocaecal valve

Answer: A) Epiglottis
Explanation: The epiglottis is a flap of tissue that covers the trachea (windpipe) during swallowing. It ensures that food and liquids are directed into the esophagus, preventing aspiration into the lungs.

21. Which of the following is a major function of the liver?

  • A) Producing digestive enzymes
  • B) Storing bile
  • C) Synthesizing proteins and detoxifying harmful substances
  • D) Absorbing nutrients

Answer: C) Synthesizing proteins and detoxifying harmful substances
Explanation: The liver is responsible for synthesizing vital proteins like albumin and clotting factors, storing glycogen, detoxifying harmful substances, and producing bile to aid in digestion.

22. Which of the following cells in the stomach secrete hydrochloric acid?

  • A) Chief cells
  • B) Parietal cells
  • C) Mucous cells
  • D) Enteroendocrine cells

Answer: B) Parietal cells
Explanation: Parietal cells in the stomach lining secrete hydrochloric acid (HCl), which lowers the pH of the stomach, activating pepsinogen to pepsin and facilitating the breakdown of food.

23. What is the main role of the mucosal layer in the stomach?

  • A) Absorbing nutrients
  • B) Protecting the stomach lining from acid
  • C) Producing digestive enzymes
  • D) Secreting bile

Answer: B) Protecting the stomach lining from acid
Explanation: The mucosal layer of the stomach secretes mucus, which forms a protective barrier to prevent the stomach lining from being damaged by the hydrochloric acid and digestive enzymes.

24. What is the primary function of the salivary glands?

  • A) To secrete insulin
  • B) To break down fats
  • C) To secrete saliva containing enzymes for digestion
  • D) To absorb nutrients

Answer: C) To secrete saliva containing enzymes for digestion
Explanation: Salivary glands secrete saliva, which contains amylase for carbohydrate digestion and mucin for lubrication. Saliva also helps in the initial breakdown of starches and moistens food for easier swallowing.

25. The ileocecal valve is located between which two parts of the digestive system?

  • A) Small intestine and large intestine
  • B) Stomach and small intestine
  • C) Small intestine and stomach
  • D) Large intestine and rectum

Answer: A) Small intestine and large intestine
Explanation: The ileocecal valve is located at the junction between the small intestine and the large intestine. It controls the flow of chyme from the ileum into the cecum and prevents the backflow of material into the small intestine.

26. What is the main function of the gallbladder?

  • A) Secretes digestive enzymes
  • B) Stores and concentrates bile
  • C) Produces insulin
  • D) Absorbs nutrients

Answer: B) Stores and concentrates bile
Explanation: The gallbladder stores and concentrates bile produced by the liver. When food, particularly fats, enters the small intestine, bile is released from the gallbladder to help emulsify and digest fats.

27. Which of the following vitamins is synthesized by bacteria in the large intestine?

  • A) Vitamin A
  • B) Vitamin C
  • C) Vitamin K
  • D) Vitamin D

Answer: C) Vitamin K
Explanation: Vitamin K is synthesized by beneficial bacteria in the large intestine. It is important for blood clotting and bone health, and is absorbed into the bloodstream from the colon.

28. Which of the following is a feature of the structure of the small intestine that aids in nutrient absorption?

  • A) Smooth muscle
  • B) Rugae
  • C) Villi and microvilli
  • D) Circular folds

Answer: C) Villi and microvilli
Explanation: The small intestine has villi and microvilli, which are small projections that significantly increase its surface area, allowing for more efficient absorption of nutrients like carbohydrates, proteins, and fats.

29. The majority of water absorption in the digestive system occurs in the:

  • A) Stomach
  • B) Small intestine
  • C) Large intestine
  • D) Mouth

Answer: C) Large intestine
Explanation: While some water is absorbed in the small intestine, the majority of water absorption occurs in the large intestine. This helps in the formation of solid feces and the conservation of water in the body.

30. The process by which food is moved through the digestive tract by alternating contractions of muscle is called:

  • A) Diffusion
  • B) Peristalsis
  • C) Absorption
  • D) Segmentation

Answer: B) Peristalsis
Explanation: Peristalsis is the coordinated, rhythmic contraction of smooth muscles in the digestive tract that propels food from the mouth through the esophagus, stomach, small intestine, and large intestine.

31. The pancreas produces bicarbonate ions that neutralize stomach acid in the duodenum. Which of the following cells secrete these bicarbonate ions?

  • A) Alpha cells
  • B) Beta cells
  • C) Ductal cells
  • D) Acinar cells

Answer: C) Ductal cells
Explanation: Ductal cells in the pancreas secrete bicarbonate ions into the duodenum. These ions neutralize the acidic chyme coming from the stomach, creating a suitable pH for the action of digestive enzymes in the small intestine.

32. What is the main function of the enzyme lactase?

  • A) Breaking down proteins
  • B) Digestion of starches
  • C) Breaking down lactose into glucose and galactose
  • D) Emulsifying fats

Answer: C) Breaking down lactose into glucose and galactose
Explanation: Lactase is an enzyme that breaks down lactose, a sugar found in milk, into its component sugars, glucose and galactose. Deficiency in lactase leads to lactose intolerance, where undigested lactose causes gastrointestinal symptoms.

33. Which of the following is the primary component of gastric juice in the stomach?

  • A) Pepsinogen
  • B) Hydrochloric acid
  • C) Bile
  • D) Amylase

Answer: B) Hydrochloric acid
Explanation: Hydrochloric acid (HCl) is the primary component of gastric juice. It lowers the pH of the stomach to activate pepsinogen to pepsin, which is essential for protein digestion and for killing ingested pathogens.

34. The secretion of digestive enzymes from the pancreas is stimulated by which hormone?

  • A) Insulin
  • B) Gastrin
  • C) Secretin
  • D) Cholecystokinin (CCK)

Answer: D) Cholecystokinin (CCK)
Explanation: Cholecystokinin (CCK) is a hormone released from the small intestine in response to the presence of fats and proteins. It stimulates the pancreas to secrete digestive enzymes and the gallbladder to release bile into the duodenum.

35. What is the primary role of the duodenum in digestion?

  • A) Absorption of water
  • B) Chemical digestion and neutralization of stomach acids
  • C) Storage of bile
  • D) Synthesis of digestive enzymes

Answer: B) Chemical digestion and neutralization of stomach acids
Explanation: The duodenum is the first part of the small intestine, where most chemical digestion takes place. It receives bile and pancreatic enzymes, and its mucosa produces secretions that neutralize stomach acids.

36. Which of the following is responsible for the "flavor" of food?

  • A) Taste buds
  • B) Saliva
  • C) Villi
  • D) Mucus

Answer: A) Taste buds
Explanation: Taste buds are sensory organs located on the tongue and in the mouth. They detect the five basic tastes: sweet, salty, sour, bitter, and umami, which contribute to the flavor perception of food.

37. What type of cell in the stomach secretes pepsinogen?

  • A) Parietal cells
  • B) Chief cells
  • C) G cells
  • D) Enteroendocrine cells

Answer: B) Chief cells
Explanation: Chief cells in the stomach secrete pepsinogen, an inactive precursor of pepsin. When exposed to hydrochloric acid, pepsinogen is converted into pepsin, which is the enzyme responsible for protein digestion.

38. Which of the following processes occurs in the large intestine?

  • A) Protein digestion
  • B) Absorption of most nutrients
  • C) Fermentation of undigested carbohydrates
  • D) Bile production

Answer: C) Fermentation of undigested carbohydrates
Explanation: The large intestine hosts bacteria that ferment undigested carbohydrates, producing gases and short-chain fatty acids. These products can be absorbed and contribute to energy metabolism.

39. What is the main purpose of the rugae in the stomach?

  • A) Increase surface area for nutrient absorption
  • B) Protect the stomach lining from acid
  • C) Allow the stomach to expand as it fills with food
  • D) Secrete digestive enzymes

Answer: C) Allow the stomach to expand as it fills with food
Explanation: The rugae are folds in the stomach lining that allow the stomach to expand as it fills with food. This helps the stomach accommodate varying volumes of food while maintaining its surface area for digestion.

40. Which hormone is primarily responsible for stimulating the secretion of gastric acid?

  • A) Secretin
  • B) Cholecystokinin
  • C) Gastrin
  • D) Insulin

Answer: C) Gastrin
Explanation: Gastrin is a hormone produced by G cells in the stomach. It stimulates the parietal cells to secrete hydrochloric acid, which is essential for protein digestion and creating the acidic environment necessary for enzyme activation.

41. Which of the following is the main digestive enzyme responsible for breaking down proteins in the stomach?

  • A) Pepsin
  • B) Amylase
  • C) Lipase
  • D) Trypsin

Answer: A) Pepsin
Explanation: Pepsin is the main enzyme in the stomach responsible for breaking down proteins into smaller peptides. It is secreted as pepsinogen and is activated by the acidic environment in the stomach.

42. Which section of the small intestine is primarily responsible for the absorption of nutrients?

  • A) Duodenum
  • B) Jejunum
  • C) Ileum
  • D) Cecum

Answer: B) Jejunum
Explanation: The jejunum is the middle section of the small intestine and is primarily responsible for nutrient absorption. It has a highly vascularized lining with villi to maximize nutrient uptake into the bloodstream.

43. Which of the following cells in the stomach are responsible for secreting mucus to protect the stomach lining?

  • A) Chief cells
  • B) Parietal cells
  • C) Mucous cells
  • D) Enteroendocrine cells

Answer: C) Mucous cells
Explanation: Mucous cells secrete mucus in the stomach, which forms a protective barrier on the stomach lining, preventing damage from the hydrochloric acid and digestive enzymes like pepsin.

44. What is the main role of the large intestine in digestion?

  • A) Absorption of nutrients
  • B) Production of digestive enzymes
  • C) Absorption of water and electrolytes
  • D) Neutralization of stomach acids

Answer: C) Absorption of water and electrolytes
Explanation: The large intestine’s main function is the absorption of water and electrolytes from the remaining indigestible food matter, transforming it into solid feces. It also plays a role in fermentation and synthesis of certain vitamins.

45. The enzyme peptidase is involved in the digestion of:

  • A) Carbohydrates
  • B) Proteins
  • C) Fats
  • D) Nucleic acids

Answer: B) Proteins
Explanation: Peptidases (or proteases) are enzymes that break down peptides into amino acids. These enzymes are active in the small intestine and are crucial for the digestion of proteins from food.

46. Which of the following structures absorbs the majority of the nutrients from digested food?

  • A) Stomach
  • B) Duodenum
  • C) Jejunum
  • D) Cecum

Answer: C) Jejunum
Explanation: The jejunum, with its numerous villi and microvilli, is the primary site of nutrient absorption in the small intestine. It absorbs most of the nutrients from the digested food, including carbohydrates, proteins, and fats.

47. What triggers the release of bile from the gallbladder into the duodenum?

  • A) Secretin
  • B) Gastrin
  • C) Cholecystokinin (CCK)
  • D) Insulin

Answer: C) Cholecystokinin (CCK)
Explanation: Cholecystokinin (CCK) is released from the small intestine in response to the presence of fats and proteins in the chyme. It stimulates the gallbladder to contract and release bile into the duodenum to emulsify fats for digestion.

48. The enzyme amylase primarily breaks down which macronutrient?

  • A) Carbohydrates
  • B) Proteins
  • C) Fats
  • D) Nucleic acids

Answer: A) Carbohydrates
Explanation: Amylase is an enzyme that begins the digestion of carbohydrates by breaking down starches into simpler sugars like maltose. It is produced in the salivary glands and the pancreas.

49. The role of the enteric nervous system in the digestive system is to:

  • A) Stimulate secretion of digestive enzymes
  • B) Control the movement of food through the gastrointestinal tract
  • C) Produce bile for fat digestion
  • D) Regulate blood glucose levels

Answer: B) Control the movement of food through the gastrointestinal tract
Explanation: The enteric nervous system is often referred to as the "second brain" of the body. It regulates the motility (movement) of the gastrointestinal tract and coordinates digestive processes, such as peristalsis and segmentation.

50. Which part of the digestive system stores bile before it is released into the duodenum?

  • A) Liver
  • B) Pancreas
  • C) Gallbladder
  • D) Duodenum

Answer: C) Gallbladder
Explanation: The gallbladder stores bile produced by the liver. When needed, particularly after the ingestion of fatty foods, it contracts to release bile into the duodenum, where it aids in the emulsification of fats.

51. Which of the following substances is primarily responsible for the emulsification of fats in the digestive system?

  • A) Amylase
  • B) Pepsin
  • C) Bile
  • D) Lactase

Answer: C) Bile
Explanation: Bile, produced by the liver and stored in the gallbladder, emulsifies fats, breaking them down into smaller droplets. This increases the surface area for enzymes, like lipase, to effectively digest the fats in the small intestine.

52. Which of the following is the correct sequence of the digestive tract from mouth to anus?

  • A) Stomach → Large intestine → Small intestine → Mouth → Esophagus
  • B) Mouth → Esophagus → Stomach → Small intestine → Large intestine
  • C) Small intestine → Stomach → Esophagus → Mouth → Large intestine
  • D) Esophagus → Mouth → Small intestine → Large intestine → Stomach

Answer: B) Mouth → Esophagus → Stomach → Small intestine → Large intestine
Explanation: The correct order of digestion is: food enters the mouth, travels down the esophagus to the stomach, then into the small intestine for absorption, and finally, any remaining material enters the large intestine before being excreted.

53. Which of the following is a function of hydrochloric acid in the stomach?

  • A) Activates pepsinogen into pepsin
  • B) Emulsifies fats
  • C) Breaks down carbohydrates
  • D) Neutralizes stomach acid

Answer: A) Activates pepsinogen into pepsin
Explanation: Hydrochloric acid in the stomach lowers the pH, which activates pepsinogen (secreted by chief cells) into pepsin. Pepsin then breaks down proteins into smaller peptides.

54. Which hormone stimulates the pancreas to release digestive enzymes and bicarbonate?

  • A) Gastrin
  • B) Secretin
  • C) Cholecystokinin
  • D) Insulin

Answer: B) Secretin
Explanation: Secretin is released by the duodenum in response to acidic chyme entering from the stomach. It stimulates the pancreas to release bicarbonate to neutralize stomach acid and digestive enzymes to aid in digestion.

55. Which of the following is a function of the intestinal villi?

  • A) Absorption of nutrients
  • B) Secretion of digestive enzymes
  • C) Storage of bile
  • D) Production of hydrochloric acid

Answer: A) Absorption of nutrients
Explanation: The villi in the small intestine are finger-like projections that increase the surface area for nutrient absorption. They contain capillaries that transport absorbed nutrients into the bloodstream and lymphatic system.

56. What is the primary function of the large intestine?

  • A) Absorbing nutrients from digested food
  • B) Secreting digestive enzymes
  • C) Absorbing water and electrolytes
  • D) Producing bile

Answer: C) Absorbing water and electrolytes
Explanation: The large intestine absorbs most of the water and electrolytes from the remaining undigested food matter, converting it into solid feces for excretion. It also hosts gut bacteria that contribute to fermentation processes.

57. What is the function of the pyloric sphincter?

  • A) Prevents the backflow of stomach contents into the esophagus
  • B) Controls the release of food from the stomach to the duodenum
  • C) Stimulates the release of bile into the small intestine
  • D) Secretes digestive enzymes in the stomach

Answer: B) Controls the release of food from the stomach to the duodenum
Explanation: The pyloric sphincter controls the passage of chyme from the stomach into the duodenum. It opens to allow small amounts of partially digested food to move into the small intestine for further digestion.

58. What is the role of bile salts in the digestive process?

  • A) Neutralize stomach acid
  • B) Break down proteins
  • C) Emulsify fats
  • D) Absorb nutrients

Answer: C) Emulsify fats
Explanation: Bile salts, found in bile, play a critical role in emulsifying fats in the small intestine. By breaking fats into smaller droplets, bile salts increase the surface area for lipase to digest them more efficiently.

59. The enzyme maltase breaks down which of the following?

  • A) Sucrose
  • B) Lactose
  • C) Maltose
  • D) Fructose

Answer: C) Maltose
Explanation: Maltase is an enzyme that breaks down maltose, a disaccharide formed from starch, into two glucose molecules. This process occurs in the small intestine, allowing the body to absorb glucose for energy.

60. The majority of nutrient absorption occurs in which section of the small intestine?

  • A) Duodenum
  • B) Jejunum
  • C) Ileum
  • D) Cecum

Answer: B) Jejunum
Explanation: The jejunum is the second part of the small intestine and is primarily responsible for nutrient absorption. It has a highly vascularized lining with villi and microvilli that maximize nutrient uptake into the bloodstream.

61. Which of the following enzymes is responsible for breaking down starches into maltose?

  • A) Amylase
  • B) Pepsin
  • C) Lactase
  • D) Lipase

Answer: A) Amylase
Explanation: Amylase is the enzyme responsible for breaking down starches (complex carbohydrates) into simpler sugars like maltose. It is produced in the salivary glands and pancreas and acts primarily in the mouth and small intestine.

62. What is the primary function of the colon (large intestine)?

  • A) Digestion of food
  • B) Absorption of water and electrolytes
  • C) Secretion of digestive enzymes
  • D) Storage of bile

Answer: B) Absorption of water and electrolytes
Explanation: The colon (large intestine) primarily absorbs water, electrolytes, and some vitamins, while also fermenting undigested food residues. The remaining material is then excreted as feces.

63. Which of the following hormones stimulates the secretion of hydrochloric acid in the stomach?

  • A) Secretin
  • B) Gastrin
  • C) Cholecystokinin (CCK)
  • D) Insulin

Answer: B) Gastrin
Explanation: Gastrin is a hormone released by G cells in the stomach in response to food. It stimulates parietal cells to secrete hydrochloric acid (HCl), which helps digest food and provides an acidic environment for enzymes like pepsin.

64. Which part of the digestive system absorbs the majority of the nutrients from food?

  • A) Stomach
  • B) Large intestine
  • C) Duodenum
  • D) Small intestine

Answer: D) Small intestine
Explanation: The small intestine is the primary site for digestion and nutrient absorption. It consists of the duodenum, jejunum, and ileum, with villi and microvilli increasing the surface area for nutrient absorption into the bloodstream.

65. What is the role of the sphincter of Oddi?

  • A) Regulates the entry of food into the stomach
  • B) Controls the release of bile and pancreatic juice into the duodenum
  • C) Prevents the backflow of food into the esophagus
  • D) Stimulates the release of digestive enzymes from the pancreas

Answer: B) Controls the release of bile and pancreatic juice into the duodenum
Explanation: The sphincter of Oddi controls the flow of bile from the gallbladder and pancreatic juices into the duodenum. This is essential for the digestion of fats and other nutrients in the small intestine.

66. Which part of the digestive system produces the enzyme trypsinogen?

  • A) Stomach
  • B) Pancreas
  • C) Small intestine
  • D) Liver

Answer: B) Pancreas
Explanation: The pancreas produces trypsinogen, an inactive enzyme that is converted into active trypsin in the small intestine. Trypsin is a protease that breaks down proteins into smaller peptides and amino acids.

67. Which of the following is a feature of the stomach lining that prevents damage from hydrochloric acid?

  • A) Villi
  • B) Mucus secretion
  • C) Bile secretion
  • D) Peristalsis

Answer: B) Mucus secretion
Explanation: The stomach lining is protected by a layer of mucus secreted by mucous cells. This mucus forms a barrier that shields the stomach lining from the corrosive effects of hydrochloric acid and digestive enzymes like pepsin.

68. What is the primary role of the enzyme lipase?

  • A) Breaks down proteins into amino acids
  • B) Breaks down carbohydrates into simple sugars
  • C) Emulsifies fats for digestion
  • D) Breaks down fats into fatty acids and glycerol

Answer: D) Breaks down fats into fatty acids and glycerol
Explanation: Lipase is the enzyme that breaks down fats (lipids) into fatty acids and glycerol. It is secreted by the pancreas and acts in the small intestine, where it aids in fat digestion after bile emulsifies the fats.

69. The majority of absorption of digested nutrients takes place in which part of the small intestine?

  • A) Duodenum
  • B) Jejunum
  • C) Ileum
  • D) Cecum

Answer: B) Jejunum
Explanation: The jejunum is the middle section of the small intestine and is primarily responsible for the absorption of nutrients such as sugars, amino acids, and fatty acids. It has a large surface area with villi and microvilli for efficient absorption.

70. What is the main role of the pancreas in digestion?

  • A) Absorbs nutrients
  • B) Secretes digestive enzymes and bicarbonate
  • C) Stores bile
  • D) Produces hydrochloric acid

Answer: B) Secretes digestive enzymes and bicarbonate
Explanation: The pancreas serves both an exocrine and endocrine function. Exocrine-wise, it secretes digestive enzymes like amylase, lipase, and proteases, as well as bicarbonate to neutralize stomach acid in the small intestine.

71. Which of the following is the primary site for the digestion of carbohydrates?

  • A) Stomach
  • B) Mouth
  • C) Duodenum
  • D) Small intestine

Answer: B) Mouth
Explanation: The digestion of carbohydrates begins in the mouth, where the enzyme amylase, found in saliva, breaks down starches into smaller sugars. However, the majority of carbohydrate digestion occurs in the small intestine.

72. The enzyme lactase is responsible for the breakdown of which sugar?

  • A) Sucrose
  • B) Glucose
  • C) Lactose
  • D) Fructose

Answer: C) Lactose
Explanation: Lactase is the enzyme responsible for breaking down lactose, the sugar found in milk, into its components: glucose and galactose. Deficiency in lactase leads to lactose intolerance, where undigested lactose causes gastrointestinal discomfort.

73. Which of the following structures prevents food from entering the trachea during swallowing?

  • A) Epiglottis
  • B) Uvula
  • C) Pyloric sphincter
  • D) Cardiac sphincter

Answer: A) Epiglottis
Explanation: The epiglottis is a flap of cartilage that covers the trachea during swallowing, preventing food and liquid from entering the airway and directing it to the esophagus.

74. The function of the villi in the small intestine is to:

  • A) Secrete digestive enzymes
  • B) Absorb nutrients into the bloodstream
  • C) Neutralize stomach acid
  • D) Store bile

Answer: B) Absorb nutrients into the bloodstream
Explanation: Villi are finger-like projections in the lining of the small intestine that increase the surface area for nutrient absorption. Each villus contains capillaries and lacteals, which transport absorbed nutrients into the bloodstream and lymphatic system.

75. The primary function of the gastric glands in the stomach is to:

  • A) Secrete digestive enzymes and hydrochloric acid
  • B) Absorb nutrients
  • C) Produce bile
  • D) Store food before digestion

Answer: A) Secrete digestive enzymes and hydrochloric acid
Explanation: The gastric glands secrete hydrochloric acid (HCl), which lowers the pH of the stomach, and digestive enzymes such as pepsinogen. These are essential for protein digestion and maintaining a sterile environment in the stomach.

76. Which of the following is NOT a function of the liver?

  • A) Detoxification of harmful substances
  • B) Production of bile
  • C) Synthesis of clotting factors
  • D) Secretion of digestive enzymes

Answer: D) Secretion of digestive enzymes
Explanation: The liver is responsible for detoxifying harmful substances, producing bile for fat digestion, and synthesizing important proteins like albumin and clotting factors. However, it does not secrete digestive enzymes; this is the role of the pancreas.

77. The small intestine is made up of three sections. Which of the following is the correct order?

  • A) Duodenum, Jejunum, Ileum
  • B) Jejunum, Duodenum, Ileum
  • C) Ileum, Jejunum, Duodenum
  • D) Duodenum, Ileum, Jejunum

Answer: A) Duodenum, Jejunum, Ileum
Explanation: The small intestine is divided into three sections: the duodenum (where most chemical digestion occurs), the jejunum (primarily responsible for nutrient absorption), and the ileum (where vitamin B12 and bile salts are absorbed).

78. Which of the following is the primary role of the sphincter of Oddi?

  • A) Preventing backflow of food into the esophagus
  • B) Controlling the release of bile and pancreatic juices into the duodenum
  • C) Regulating the absorption of nutrients in the small intestine
  • D) Allowing the passage of food from the mouth to the stomach

Answer: B) Controlling the release of bile and pancreatic juices into the duodenum
Explanation: The sphincter of Oddi is a muscular valve that regulates the flow of bile and pancreatic juices from the common bile duct and pancreatic duct into the duodenum, aiding in the digestion of fats and other nutrients.

79. What is the function of the enzyme pepsin?

  • A) Breaks down proteins into amino acids
  • B) Breaks down fats into fatty acids
  • C) Breaks down carbohydrates into simple sugars
  • D) Emulsifies fats for digestion

Answer: A) Breaks down proteins into amino acids
Explanation: Pepsin is a protease enzyme secreted in an inactive form (pepsinogen) by chief cells in the stomach. It is activated by hydrochloric acid and breaks down proteins into smaller peptides and amino acids.

80. Which of the following is a characteristic feature of the large intestine?

  • A) Villi for nutrient absorption
  • B) Presence of digestive enzymes
  • C) Absorption of water and electrolytes
  • D) Production of bile

Answer: C) Absorption of water and electrolytes
Explanation: The primary function of the large intestine is to absorb water, electrolytes, and some vitamins from undigested food matter. This process converts the material into solid feces for elimination.

81. Which of the following enzymes is responsible for breaking down fats into fatty acids and glycerol?

  • A) Amylase
  • B) Pepsin
  • C) Lipase
  • D) Lactase

Answer: C) Lipase
Explanation: Lipase is the enzyme responsible for breaking down fats (lipids) into fatty acids and glycerol. It is secreted by the pancreas and acts in the small intestine after bile emulsifies the fats.

82. Which of the following hormones stimulates the release of gastric acid in the stomach?

  • A) Secretin
  • B) Gastrin
  • C) Cholecystokinin (CCK)
  • D) Insulin

Answer: B) Gastrin
Explanation: Gastrin is a hormone produced by G cells in the stomach. It stimulates the parietal cells of the stomach to secrete hydrochloric acid, which is essential for digestion and maintaining an acidic environment for enzyme activity.

83. Which of the following is the main function of the pancreas in digestion?

  • A) Secretion of bile
  • B) Secretion of digestive enzymes
  • C) Absorption of nutrients
  • D) Neutralizing stomach acid

Answer: B) Secretion of digestive enzymes
Explanation: The pancreas produces digestive enzymes (amylase, lipase, proteases) that help break down carbohydrates, fats, and proteins in the small intestine. It also secretes bicarbonate to neutralize stomach acid entering the duodenum.

84. What is the role of the pyloric sphincter?

  • A) Controls the release of bile into the duodenum
  • B) Prevents the backflow of stomach contents into the esophagus
  • C) Regulates the passage of food from the stomach to the small intestine
  • D) Stimulates the release of digestive enzymes

Answer: C) Regulates the passage of food from the stomach to the small intestine
Explanation: The pyloric sphincter controls the movement of chyme from the stomach into the duodenum. It ensures that food is released in small amounts to allow proper digestion and nutrient absorption.

85. Which section of the small intestine is primarily responsible for absorbing most nutrients?

  • A) Duodenum
  • B) Jejunum
  • C) Ileum
  • D) Cecum

Answer: B) Jejunum
Explanation: The jejunum is the middle section of the small intestine and is primarily responsible for nutrient absorption. Its lining is equipped with villi and microvilli to increase the surface area for absorption of carbohydrates, proteins, and lipids.

86. The enzyme trypsin is involved in the digestion of:

  • A) Carbohydrates
  • B) Proteins
  • C) Fats
  • D) Nucleic acids

Answer: B) Proteins
Explanation: Trypsin is a protease enzyme secreted by the pancreas in an inactive form (trypsinogen) and activated in the small intestine. It breaks down proteins into smaller peptides and amino acids.

87. What is the primary role of bile in digestion?

  • A) Neutralizing stomach acid
  • B) Breaking down carbohydrates
  • C) Emulsifying fats for digestion
  • D) Absorbing water and electrolytes

Answer: C) Emulsifying fats for digestion
Explanation: Bile, produced by the liver and stored in the gallbladder, emulsifies fats in the small intestine. This process breaks fats into smaller droplets, increasing the surface area for enzymes like lipase to digest the fats.

88. What is the function of the large intestine in the digestive process?

  • A) Absorption of nutrients
  • B) Storage of bile
  • C) Absorption of water and electrolytes
  • D) Breakdown of fats

Answer: C) Absorption of water and electrolytes
Explanation: The large intestine is primarily responsible for absorbing water and electrolytes from the remaining indigestible food material. It also houses gut bacteria that contribute to fermentation and synthesis of some vitamins, such as vitamin K.

89. Which of the following is true about the function of the epiglottis?

  • A) It secretes digestive enzymes in the stomach
  • B) It prevents food from entering the trachea during swallowing
  • C) It regulates the release of bile into the duodenum
  • D) It produces insulin for glucose regulation

Answer: B) It prevents food from entering the trachea during swallowing
Explanation: The epiglottis is a flap of cartilage that closes over the trachea during swallowing to prevent food and liquids from entering the airway, directing them instead to the esophagus for digestion.

90. Which enzyme is responsible for the digestion of proteins in the stomach?

  • A) Amylase
  • B) Pepsin
  • C) Lipase
  • D) Trypsin

Answer: B) Pepsin
Explanation: Pepsin is the enzyme responsible for breaking down proteins into smaller peptides in the acidic environment of the stomach. It is secreted as pepsinogen by chief cells and activated by hydrochloric acid.

91. Which of the following substances is produced by the liver to aid in fat digestion?

  • A) Amylase
  • B) Pepsin
  • C) Bile
  • D) Insulin

Answer: C) Bile
Explanation: The liver produces bile, which is stored in the gallbladder and released into the duodenum. Bile helps emulsify fats, breaking them down into smaller droplets to increase the surface area for digestion by enzymes like lipase.

92. The enzyme salivary amylase is secreted by which of the following?

  • A) Stomach
  • B) Pancreas
  • C) Salivary glands
  • D) Liver

Answer: C) Salivary glands
Explanation: Salivary amylase is produced by the salivary glands and begins the process of carbohydrate digestion in the mouth. It breaks down starches into smaller sugars, such as maltose, as the food is chewed.

93. The primary function of the ileum is to:

  • A) Absorb most nutrients
  • B) Absorb water and electrolytes
  • C) Emulsify fats
  • D) Digest proteins

Answer: A) Absorb most nutrients
Explanation: The ileum, the final part of the small intestine, is primarily responsible for the absorption of nutrients, including bile salts and vitamin B12. It absorbs the remaining nutrients that were not absorbed by the jejunum.

94. The process of moving food through the digestive tract is known as:

  • A) Absorption
  • B) Peristalsis
  • C) Emulsification
  • D) Secretion

Answer: B) Peristalsis
Explanation: Peristalsis is the series of wave-like muscle contractions that move food along the digestive tract, from the esophagus to the stomach, and through the small and large intestines.

95. Which of the following digestive enzymes is responsible for breaking down proteins into smaller peptides?

  • A) Amylase
  • B) Pepsin
  • C) Lipase
  • D) Maltase

Answer: B) Pepsin
Explanation: Pepsin is a digestive enzyme in the stomach that breaks down proteins into smaller peptides. It is activated from its inactive form, pepsinogen, by the acidic environment of the stomach.

96. Which of the following is the function of the gallbladder?

  • A) Produce digestive enzymes
  • B) Store and concentrate bile
  • C) Produce insulin
  • D) Absorb nutrients

Answer: B) Store and concentrate bile
Explanation: The gallbladder stores bile produced by the liver. It concentrates the bile and releases it into the duodenum when fat is present in the small intestine, aiding in the digestion and absorption of fats.

97. What triggers the release of cholecystokinin (CCK)?

  • A) Presence of fats and proteins in the stomach
  • B) Presence of bile in the small intestine
  • C) Acidic chyme entering the duodenum
  • D) The presence of carbohydrates in the stomach

Answer: A) Presence of fats and proteins in the stomach
Explanation: Cholecystokinin (CCK) is released from the small intestine in response to the presence of fats and proteins. It stimulates the gallbladder to release bile and the pancreas to secrete digestive enzymes.

98. Which of the following is the primary site of nutrient absorption in the digestive system?

  • A) Large intestine
  • B) Small intestine
  • C) Stomach
  • D) Esophagus

Answer: B) Small intestine
Explanation: The small intestine is the primary site for nutrient absorption. The duodenum, jejunum, and ileum have villi and microvilli that increase surface area for the absorption of carbohydrates, proteins, lipids, and other nutrients.

99. Which of the following is true regarding the pancreas?

  • A) It produces bile to aid fat digestion
  • B) It secretes digestive enzymes and bicarbonate to neutralize stomach acid
  • C) It stores bile for release into the duodenum
  • D) It absorbs nutrients from the digested food

Answer: B) It secretes digestive enzymes and bicarbonate to neutralize stomach acid
Explanation: The pancreas secretes enzymes like amylase, lipase, and proteases to digest carbohydrates, fats, and proteins, respectively. It also produces bicarbonate to neutralize the acidic chyme from the stomach entering the duodenum.

100. What is the role of hydrochloric acid (HCl) in the stomach?

  • A) Break down carbohydrates
  • B) Neutralize stomach acid
  • C) Activate pepsinogen into pepsin
  • D) Absorb nutrients

Answer: C) Activate pepsinogen into pepsin
Explanation: Hydrochloric acid (HCl) in the stomach activates the enzyme pepsinogen into its active form, pepsin. Pepsin is essential for breaking down proteins into smaller peptides in the acidic environment of the stomach.

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